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814 lines
22 KiB
814 lines
22 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* ePAPR hypervisor byte channel device driver |
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* |
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* Copyright 2009-2011 Freescale Semiconductor, Inc. |
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* |
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* Author: Timur Tabi <[email protected]> |
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* |
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* This driver support three distinct interfaces, all of which are related to |
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* ePAPR hypervisor byte channels. |
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* |
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* 1) An early-console (udbg) driver. This provides early console output |
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* through a byte channel. The byte channel handle must be specified in a |
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* Kconfig option. |
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* |
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* 2) A normal console driver. Output is sent to the byte channel designated |
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* for stdout in the device tree. The console driver is for handling kernel |
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* printk calls. |
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* |
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* 3) A tty driver, which is used to handle user-space input and output. The |
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* byte channel used for the console is designated as the default tty. |
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*/ |
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|
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#include <linux/init.h> |
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#include <linux/slab.h> |
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#include <linux/err.h> |
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#include <linux/interrupt.h> |
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#include <linux/fs.h> |
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#include <linux/poll.h> |
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#include <asm/epapr_hcalls.h> |
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#include <linux/of.h> |
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#include <linux/of_irq.h> |
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#include <linux/platform_device.h> |
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#include <linux/cdev.h> |
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#include <linux/console.h> |
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#include <linux/tty.h> |
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#include <linux/tty_flip.h> |
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#include <linux/circ_buf.h> |
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#include <asm/udbg.h> |
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/* The size of the transmit circular buffer. This must be a power of two. */ |
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#define BUF_SIZE 2048 |
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|
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/* Per-byte channel private data */ |
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struct ehv_bc_data { |
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struct device *dev; |
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struct tty_port port; |
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uint32_t handle; |
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unsigned int rx_irq; |
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unsigned int tx_irq; |
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spinlock_t lock; /* lock for transmit buffer */ |
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unsigned char buf[BUF_SIZE]; /* transmit circular buffer */ |
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unsigned int head; /* circular buffer head */ |
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unsigned int tail; /* circular buffer tail */ |
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int tx_irq_enabled; /* true == TX interrupt is enabled */ |
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}; |
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/* Array of byte channel objects */ |
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static struct ehv_bc_data *bcs; |
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|
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/* Byte channel handle for stdout (and stdin), taken from device tree */ |
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static unsigned int stdout_bc; |
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/* Virtual IRQ for the byte channel handle for stdin, taken from device tree */ |
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static unsigned int stdout_irq; |
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/**************************** SUPPORT FUNCTIONS ****************************/ |
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|
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/* |
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* Enable the transmit interrupt |
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* |
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* Unlike a serial device, byte channels have no mechanism for disabling their |
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* own receive or transmit interrupts. To emulate that feature, we toggle |
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* the IRQ in the kernel. |
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* |
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* We cannot just blindly call enable_irq() or disable_irq(), because these |
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* calls are reference counted. This means that we cannot call enable_irq() |
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* if interrupts are already enabled. This can happen in two situations: |
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* |
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* 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write() |
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* 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue() |
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* |
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* To work around this, we keep a flag to tell us if the IRQ is enabled or not. |
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*/ |
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static void enable_tx_interrupt(struct ehv_bc_data *bc) |
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{ |
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if (!bc->tx_irq_enabled) { |
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enable_irq(bc->tx_irq); |
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bc->tx_irq_enabled = 1; |
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} |
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} |
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static void disable_tx_interrupt(struct ehv_bc_data *bc) |
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{ |
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if (bc->tx_irq_enabled) { |
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disable_irq_nosync(bc->tx_irq); |
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bc->tx_irq_enabled = 0; |
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} |
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} |
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/* |
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* find the byte channel handle to use for the console |
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* |
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* The byte channel to be used for the console is specified via a "stdout" |
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* property in the /chosen node. |
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*/ |
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static int find_console_handle(void) |
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{ |
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struct device_node *np = of_stdout; |
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const uint32_t *iprop; |
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|
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/* We don't care what the aliased node is actually called. We only |
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* care if it's compatible with "epapr,hv-byte-channel", because that |
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* indicates that it's a byte channel node. |
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*/ |
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if (!np || !of_device_is_compatible(np, "epapr,hv-byte-channel")) |
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return 0; |
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stdout_irq = irq_of_parse_and_map(np, 0); |
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if (stdout_irq == NO_IRQ) { |
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pr_err("ehv-bc: no 'interrupts' property in %pOF node\n", np); |
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return 0; |
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} |
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/* |
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* The 'hv-handle' property contains the handle for this byte channel. |
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*/ |
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iprop = of_get_property(np, "hv-handle", NULL); |
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if (!iprop) { |
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pr_err("ehv-bc: no 'hv-handle' property in %pOFn node\n", |
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np); |
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return 0; |
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} |
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stdout_bc = be32_to_cpu(*iprop); |
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return 1; |
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} |
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static unsigned int local_ev_byte_channel_send(unsigned int handle, |
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unsigned int *count, |
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const char *p) |
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{ |
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char buffer[EV_BYTE_CHANNEL_MAX_BYTES]; |
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unsigned int c = *count; |
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if (c < sizeof(buffer)) { |
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memcpy(buffer, p, c); |
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memset(&buffer[c], 0, sizeof(buffer) - c); |
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p = buffer; |
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} |
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return ev_byte_channel_send(handle, count, p); |
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} |
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/*************************** EARLY CONSOLE DRIVER ***************************/ |
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#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC |
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/* |
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* send a byte to a byte channel, wait if necessary |
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* |
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* This function sends a byte to a byte channel, and it waits and |
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* retries if the byte channel is full. It returns if the character |
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* has been sent, or if some error has occurred. |
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* |
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*/ |
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static void byte_channel_spin_send(const char data) |
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{ |
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int ret, count; |
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do { |
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count = 1; |
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ret = local_ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE, |
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&count, &data); |
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} while (ret == EV_EAGAIN); |
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} |
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/* |
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* The udbg subsystem calls this function to display a single character. |
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* We convert CR to a CR/LF. |
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*/ |
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static void ehv_bc_udbg_putc(char c) |
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{ |
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if (c == '\n') |
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byte_channel_spin_send('\r'); |
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byte_channel_spin_send(c); |
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} |
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/* |
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* early console initialization |
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* |
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* PowerPC kernels support an early printk console, also known as udbg. |
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* This function must be called via the ppc_md.init_early function pointer. |
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* At this point, the device tree has been unflattened, so we can obtain the |
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* byte channel handle for stdout. |
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* |
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* We only support displaying of characters (putc). We do not support |
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* keyboard input. |
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*/ |
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void __init udbg_init_ehv_bc(void) |
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{ |
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unsigned int rx_count, tx_count; |
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unsigned int ret; |
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/* Verify the byte channel handle */ |
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ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE, |
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&rx_count, &tx_count); |
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if (ret) |
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return; |
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udbg_putc = ehv_bc_udbg_putc; |
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register_early_udbg_console(); |
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udbg_printf("ehv-bc: early console using byte channel handle %u\n", |
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CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE); |
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} |
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#endif |
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/****************************** CONSOLE DRIVER ******************************/ |
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static struct tty_driver *ehv_bc_driver; |
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/* |
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* Byte channel console sending worker function. |
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* |
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* For consoles, if the output buffer is full, we should just spin until it |
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* clears. |
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*/ |
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static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s, |
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unsigned int count) |
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{ |
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unsigned int len; |
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int ret = 0; |
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while (count) { |
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len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES); |
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do { |
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ret = local_ev_byte_channel_send(handle, &len, s); |
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} while (ret == EV_EAGAIN); |
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count -= len; |
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s += len; |
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} |
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return ret; |
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} |
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/* |
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* write a string to the console |
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* |
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* This function gets called to write a string from the kernel, typically from |
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* a printk(). This function spins until all data is written. |
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* |
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* We copy the data to a temporary buffer because we need to insert a \r in |
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* front of every \n. It's more efficient to copy the data to the buffer than |
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* it is to make multiple hcalls for each character or each newline. |
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*/ |
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static void ehv_bc_console_write(struct console *co, const char *s, |
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unsigned int count) |
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{ |
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char s2[EV_BYTE_CHANNEL_MAX_BYTES]; |
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unsigned int i, j = 0; |
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char c; |
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for (i = 0; i < count; i++) { |
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c = *s++; |
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if (c == '\n') |
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s2[j++] = '\r'; |
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s2[j++] = c; |
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if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) { |
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if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j)) |
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return; |
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j = 0; |
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} |
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} |
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if (j) |
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ehv_bc_console_byte_channel_send(stdout_bc, s2, j); |
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} |
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/* |
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* When /dev/console is opened, the kernel iterates the console list looking |
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* for one with ->device and then calls that method. On success, it expects |
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* the passed-in int* to contain the minor number to use. |
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*/ |
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static struct tty_driver *ehv_bc_console_device(struct console *co, int *index) |
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{ |
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*index = co->index; |
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return ehv_bc_driver; |
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} |
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static struct console ehv_bc_console = { |
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.name = "ttyEHV", |
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.write = ehv_bc_console_write, |
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.device = ehv_bc_console_device, |
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.flags = CON_PRINTBUFFER | CON_ENABLED, |
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}; |
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/* |
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* Console initialization |
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* |
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* This is the first function that is called after the device tree is |
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* available, so here is where we determine the byte channel handle and IRQ for |
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* stdout/stdin, even though that information is used by the tty and character |
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* drivers. |
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*/ |
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static int __init ehv_bc_console_init(void) |
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{ |
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if (!find_console_handle()) { |
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pr_debug("ehv-bc: stdout is not a byte channel\n"); |
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return -ENODEV; |
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} |
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#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC |
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/* Print a friendly warning if the user chose the wrong byte channel |
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* handle for udbg. |
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*/ |
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if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE) |
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pr_warn("ehv-bc: udbg handle %u is not the stdout handle\n", |
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CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE); |
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#endif |
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/* add_preferred_console() must be called before register_console(), |
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otherwise it won't work. However, we don't want to enumerate all the |
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byte channels here, either, since we only care about one. */ |
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add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL); |
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register_console(&ehv_bc_console); |
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pr_info("ehv-bc: registered console driver for byte channel %u\n", |
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stdout_bc); |
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return 0; |
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} |
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console_initcall(ehv_bc_console_init); |
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/******************************** TTY DRIVER ********************************/ |
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/* |
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* byte channel receive interrupt handler |
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* |
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* This ISR is called whenever data is available on a byte channel. |
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*/ |
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static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data) |
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{ |
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struct ehv_bc_data *bc = data; |
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unsigned int rx_count, tx_count, len; |
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int count; |
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char buffer[EV_BYTE_CHANNEL_MAX_BYTES]; |
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int ret; |
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/* Find out how much data needs to be read, and then ask the TTY layer |
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* if it can handle that much. We want to ensure that every byte we |
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* read from the byte channel will be accepted by the TTY layer. |
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*/ |
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ev_byte_channel_poll(bc->handle, &rx_count, &tx_count); |
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count = tty_buffer_request_room(&bc->port, rx_count); |
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/* 'count' is the maximum amount of data the TTY layer can accept at |
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* this time. However, during testing, I was never able to get 'count' |
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* to be less than 'rx_count'. I'm not sure whether I'm calling it |
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* correctly. |
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*/ |
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while (count > 0) { |
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len = min_t(unsigned int, count, sizeof(buffer)); |
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/* Read some data from the byte channel. This function will |
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* never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes. |
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*/ |
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ev_byte_channel_receive(bc->handle, &len, buffer); |
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/* 'len' is now the amount of data that's been received. 'len' |
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* can't be zero, and most likely it's equal to one. |
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*/ |
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/* Pass the received data to the tty layer. */ |
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ret = tty_insert_flip_string(&bc->port, buffer, len); |
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/* 'ret' is the number of bytes that the TTY layer accepted. |
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* If it's not equal to 'len', then it means the buffer is |
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* full, which should never happen. If it does happen, we can |
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* exit gracefully, but we drop the last 'len - ret' characters |
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* that we read from the byte channel. |
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*/ |
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if (ret != len) |
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break; |
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count -= len; |
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} |
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/* Tell the tty layer that we're done. */ |
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tty_flip_buffer_push(&bc->port); |
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return IRQ_HANDLED; |
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} |
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/* |
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* dequeue the transmit buffer to the hypervisor |
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* |
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* This function, which can be called in interrupt context, dequeues as much |
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* data as possible from the transmit buffer to the byte channel. |
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*/ |
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static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc) |
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{ |
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unsigned int count; |
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unsigned int len, ret; |
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unsigned long flags; |
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do { |
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spin_lock_irqsave(&bc->lock, flags); |
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len = min_t(unsigned int, |
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CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE), |
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EV_BYTE_CHANNEL_MAX_BYTES); |
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ret = local_ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail); |
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/* 'len' is valid only if the return code is 0 or EV_EAGAIN */ |
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if (!ret || (ret == EV_EAGAIN)) |
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bc->tail = (bc->tail + len) & (BUF_SIZE - 1); |
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count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE); |
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spin_unlock_irqrestore(&bc->lock, flags); |
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} while (count && !ret); |
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spin_lock_irqsave(&bc->lock, flags); |
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if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE)) |
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/* |
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* If we haven't emptied the buffer, then enable the TX IRQ. |
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* We'll get an interrupt when there's more room in the |
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* hypervisor's output buffer. |
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*/ |
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enable_tx_interrupt(bc); |
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else |
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disable_tx_interrupt(bc); |
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spin_unlock_irqrestore(&bc->lock, flags); |
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} |
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/* |
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* byte channel transmit interrupt handler |
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* |
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* This ISR is called whenever space becomes available for transmitting |
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* characters on a byte channel. |
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*/ |
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static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data) |
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{ |
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struct ehv_bc_data *bc = data; |
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ehv_bc_tx_dequeue(bc); |
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tty_port_tty_wakeup(&bc->port); |
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return IRQ_HANDLED; |
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} |
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/* |
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* This function is called when the tty layer has data for us send. We store |
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* the data first in a circular buffer, and then dequeue as much of that data |
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* as possible. |
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* |
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* We don't need to worry about whether there is enough room in the buffer for |
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* all the data. The purpose of ehv_bc_tty_write_room() is to tell the tty |
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* layer how much data it can safely send to us. We guarantee that |
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* ehv_bc_tty_write_room() will never lie, so the tty layer will never send us |
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* too much data. |
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*/ |
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static int ehv_bc_tty_write(struct tty_struct *ttys, const unsigned char *s, |
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int count) |
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{ |
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struct ehv_bc_data *bc = ttys->driver_data; |
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unsigned long flags; |
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unsigned int len; |
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unsigned int written = 0; |
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while (1) { |
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spin_lock_irqsave(&bc->lock, flags); |
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len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE); |
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if (count < len) |
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len = count; |
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if (len) { |
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memcpy(bc->buf + bc->head, s, len); |
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bc->head = (bc->head + len) & (BUF_SIZE - 1); |
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} |
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spin_unlock_irqrestore(&bc->lock, flags); |
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if (!len) |
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break; |
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s += len; |
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count -= len; |
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written += len; |
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} |
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ehv_bc_tx_dequeue(bc); |
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return written; |
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} |
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|
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/* |
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* This function can be called multiple times for a given tty_struct, which is |
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* why we initialize bc->ttys in ehv_bc_tty_port_activate() instead. |
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* |
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* The tty layer will still call this function even if the device was not |
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* registered (i.e. tty_register_device() was not called). This happens |
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* because tty_register_device() is optional and some legacy drivers don't |
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* use it. So we need to check for that. |
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*/ |
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static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp) |
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{ |
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struct ehv_bc_data *bc = &bcs[ttys->index]; |
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if (!bc->dev) |
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return -ENODEV; |
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return tty_port_open(&bc->port, ttys, filp); |
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} |
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|
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/* |
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* Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will |
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* still call this function to close the tty device. So we can't assume that |
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* the tty port has been initialized. |
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*/ |
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static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp) |
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{ |
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struct ehv_bc_data *bc = &bcs[ttys->index]; |
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|
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if (bc->dev) |
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tty_port_close(&bc->port, ttys, filp); |
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} |
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|
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/* |
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* Return the amount of space in the output buffer |
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* |
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* This is actually a contract between the driver and the tty layer outlining |
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* how much write room the driver can guarantee will be sent OR BUFFERED. This |
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* driver MUST honor the return value. |
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*/ |
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static int ehv_bc_tty_write_room(struct tty_struct *ttys) |
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{ |
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struct ehv_bc_data *bc = ttys->driver_data; |
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unsigned long flags; |
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int count; |
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|
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spin_lock_irqsave(&bc->lock, flags); |
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count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE); |
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spin_unlock_irqrestore(&bc->lock, flags); |
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return count; |
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} |
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|
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/* |
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* Stop sending data to the tty layer |
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* |
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* This function is called when the tty layer's input buffers are getting full, |
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* so the driver should stop sending it data. The easiest way to do this is to |
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* disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being |
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* called. |
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* |
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* The hypervisor will continue to queue up any incoming data. If there is any |
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* data in the queue when the RX interrupt is enabled, we'll immediately get an |
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* RX interrupt. |
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*/ |
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static void ehv_bc_tty_throttle(struct tty_struct *ttys) |
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{ |
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struct ehv_bc_data *bc = ttys->driver_data; |
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|
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disable_irq(bc->rx_irq); |
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} |
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|
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/* |
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* Resume sending data to the tty layer |
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* |
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* This function is called after previously calling ehv_bc_tty_throttle(). The |
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* tty layer's input buffers now have more room, so the driver can resume |
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* sending it data. |
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*/ |
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static void ehv_bc_tty_unthrottle(struct tty_struct *ttys) |
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{ |
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struct ehv_bc_data *bc = ttys->driver_data; |
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|
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/* If there is any data in the queue when the RX interrupt is enabled, |
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* we'll immediately get an RX interrupt. |
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*/ |
|
enable_irq(bc->rx_irq); |
|
} |
|
|
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static void ehv_bc_tty_hangup(struct tty_struct *ttys) |
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{ |
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struct ehv_bc_data *bc = ttys->driver_data; |
|
|
|
ehv_bc_tx_dequeue(bc); |
|
tty_port_hangup(&bc->port); |
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} |
|
|
|
/* |
|
* TTY driver operations |
|
* |
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* If we could ask the hypervisor how much data is still in the TX buffer, or |
|
* at least how big the TX buffers are, then we could implement the |
|
* .wait_until_sent and .chars_in_buffer functions. |
|
*/ |
|
static const struct tty_operations ehv_bc_ops = { |
|
.open = ehv_bc_tty_open, |
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.close = ehv_bc_tty_close, |
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.write = ehv_bc_tty_write, |
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.write_room = ehv_bc_tty_write_room, |
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.throttle = ehv_bc_tty_throttle, |
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.unthrottle = ehv_bc_tty_unthrottle, |
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.hangup = ehv_bc_tty_hangup, |
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}; |
|
|
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/* |
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* initialize the TTY port |
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* |
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* This function will only be called once, no matter how many times |
|
* ehv_bc_tty_open() is called. That's why we register the ISR here, and also |
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* why we initialize tty_struct-related variables here. |
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*/ |
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static int ehv_bc_tty_port_activate(struct tty_port *port, |
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struct tty_struct *ttys) |
|
{ |
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struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port); |
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int ret; |
|
|
|
ttys->driver_data = bc; |
|
|
|
ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc); |
|
if (ret < 0) { |
|
dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n", |
|
bc->rx_irq, ret); |
|
return ret; |
|
} |
|
|
|
/* request_irq also enables the IRQ */ |
|
bc->tx_irq_enabled = 1; |
|
|
|
ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc); |
|
if (ret < 0) { |
|
dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n", |
|
bc->tx_irq, ret); |
|
free_irq(bc->rx_irq, bc); |
|
return ret; |
|
} |
|
|
|
/* The TX IRQ is enabled only when we can't write all the data to the |
|
* byte channel at once, so by default it's disabled. |
|
*/ |
|
disable_tx_interrupt(bc); |
|
|
|
return 0; |
|
} |
|
|
|
static void ehv_bc_tty_port_shutdown(struct tty_port *port) |
|
{ |
|
struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port); |
|
|
|
free_irq(bc->tx_irq, bc); |
|
free_irq(bc->rx_irq, bc); |
|
} |
|
|
|
static const struct tty_port_operations ehv_bc_tty_port_ops = { |
|
.activate = ehv_bc_tty_port_activate, |
|
.shutdown = ehv_bc_tty_port_shutdown, |
|
}; |
|
|
|
static int ehv_bc_tty_probe(struct platform_device *pdev) |
|
{ |
|
struct device_node *np = pdev->dev.of_node; |
|
struct ehv_bc_data *bc; |
|
const uint32_t *iprop; |
|
unsigned int handle; |
|
int ret; |
|
static unsigned int index = 1; |
|
unsigned int i; |
|
|
|
iprop = of_get_property(np, "hv-handle", NULL); |
|
if (!iprop) { |
|
dev_err(&pdev->dev, "no 'hv-handle' property in %pOFn node\n", |
|
np); |
|
return -ENODEV; |
|
} |
|
|
|
/* We already told the console layer that the index for the console |
|
* device is zero, so we need to make sure that we use that index when |
|
* we probe the console byte channel node. |
|
*/ |
|
handle = be32_to_cpu(*iprop); |
|
i = (handle == stdout_bc) ? 0 : index++; |
|
bc = &bcs[i]; |
|
|
|
bc->handle = handle; |
|
bc->head = 0; |
|
bc->tail = 0; |
|
spin_lock_init(&bc->lock); |
|
|
|
bc->rx_irq = irq_of_parse_and_map(np, 0); |
|
bc->tx_irq = irq_of_parse_and_map(np, 1); |
|
if ((bc->rx_irq == NO_IRQ) || (bc->tx_irq == NO_IRQ)) { |
|
dev_err(&pdev->dev, "no 'interrupts' property in %pOFn node\n", |
|
np); |
|
ret = -ENODEV; |
|
goto error; |
|
} |
|
|
|
tty_port_init(&bc->port); |
|
bc->port.ops = &ehv_bc_tty_port_ops; |
|
|
|
bc->dev = tty_port_register_device(&bc->port, ehv_bc_driver, i, |
|
&pdev->dev); |
|
if (IS_ERR(bc->dev)) { |
|
ret = PTR_ERR(bc->dev); |
|
dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret); |
|
goto error; |
|
} |
|
|
|
dev_set_drvdata(&pdev->dev, bc); |
|
|
|
dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n", |
|
ehv_bc_driver->name, i, bc->handle); |
|
|
|
return 0; |
|
|
|
error: |
|
tty_port_destroy(&bc->port); |
|
irq_dispose_mapping(bc->tx_irq); |
|
irq_dispose_mapping(bc->rx_irq); |
|
|
|
memset(bc, 0, sizeof(struct ehv_bc_data)); |
|
return ret; |
|
} |
|
|
|
static const struct of_device_id ehv_bc_tty_of_ids[] = { |
|
{ .compatible = "epapr,hv-byte-channel" }, |
|
{} |
|
}; |
|
|
|
static struct platform_driver ehv_bc_tty_driver = { |
|
.driver = { |
|
.name = "ehv-bc", |
|
.of_match_table = ehv_bc_tty_of_ids, |
|
.suppress_bind_attrs = true, |
|
}, |
|
.probe = ehv_bc_tty_probe, |
|
}; |
|
|
|
/** |
|
* ehv_bc_init - ePAPR hypervisor byte channel driver initialization |
|
* |
|
* This function is called when this driver is loaded. |
|
*/ |
|
static int __init ehv_bc_init(void) |
|
{ |
|
struct device_node *np; |
|
unsigned int count = 0; /* Number of elements in bcs[] */ |
|
int ret; |
|
|
|
pr_info("ePAPR hypervisor byte channel driver\n"); |
|
|
|
/* Count the number of byte channels */ |
|
for_each_compatible_node(np, NULL, "epapr,hv-byte-channel") |
|
count++; |
|
|
|
if (!count) |
|
return -ENODEV; |
|
|
|
/* The array index of an element in bcs[] is the same as the tty index |
|
* for that element. If you know the address of an element in the |
|
* array, then you can use pointer math (e.g. "bc - bcs") to get its |
|
* tty index. |
|
*/ |
|
bcs = kcalloc(count, sizeof(struct ehv_bc_data), GFP_KERNEL); |
|
if (!bcs) |
|
return -ENOMEM; |
|
|
|
ehv_bc_driver = alloc_tty_driver(count); |
|
if (!ehv_bc_driver) { |
|
ret = -ENOMEM; |
|
goto err_free_bcs; |
|
} |
|
|
|
ehv_bc_driver->driver_name = "ehv-bc"; |
|
ehv_bc_driver->name = ehv_bc_console.name; |
|
ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE; |
|
ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE; |
|
ehv_bc_driver->init_termios = tty_std_termios; |
|
ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV; |
|
tty_set_operations(ehv_bc_driver, &ehv_bc_ops); |
|
|
|
ret = tty_register_driver(ehv_bc_driver); |
|
if (ret) { |
|
pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret); |
|
goto err_put_tty_driver; |
|
} |
|
|
|
ret = platform_driver_register(&ehv_bc_tty_driver); |
|
if (ret) { |
|
pr_err("ehv-bc: could not register platform driver (ret=%i)\n", |
|
ret); |
|
goto err_deregister_tty_driver; |
|
} |
|
|
|
return 0; |
|
|
|
err_deregister_tty_driver: |
|
tty_unregister_driver(ehv_bc_driver); |
|
err_put_tty_driver: |
|
put_tty_driver(ehv_bc_driver); |
|
err_free_bcs: |
|
kfree(bcs); |
|
|
|
return ret; |
|
} |
|
device_initcall(ehv_bc_init);
|
|
|