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368 lines
8.8 KiB
368 lines
8.8 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Driver for the on-board character LCD found on some ARM reference boards |
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* This is basically an Hitachi HD44780 LCD with a custom IP block to drive it |
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* https://en.wikipedia.org/wiki/HD44780_Character_LCD |
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* Currently it will just display the text "ARM Linux" and the linux version |
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* |
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* Author: Linus Walleij <[email protected]> |
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*/ |
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#include <linux/init.h> |
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#include <linux/interrupt.h> |
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#include <linux/platform_device.h> |
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#include <linux/of.h> |
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#include <linux/completion.h> |
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#include <linux/delay.h> |
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#include <linux/io.h> |
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#include <linux/slab.h> |
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#include <linux/workqueue.h> |
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#include <generated/utsrelease.h> |
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#define DRIVERNAME "arm-charlcd" |
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#define CHARLCD_TIMEOUT (msecs_to_jiffies(1000)) |
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/* Offsets to registers */ |
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#define CHAR_COM 0x00U |
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#define CHAR_DAT 0x04U |
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#define CHAR_RD 0x08U |
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#define CHAR_RAW 0x0CU |
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#define CHAR_MASK 0x10U |
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#define CHAR_STAT 0x14U |
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#define CHAR_RAW_CLEAR 0x00000000U |
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#define CHAR_RAW_VALID 0x00000100U |
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/* Hitachi HD44780 display commands */ |
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#define HD_CLEAR 0x01U |
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#define HD_HOME 0x02U |
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#define HD_ENTRYMODE 0x04U |
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#define HD_ENTRYMODE_INCREMENT 0x02U |
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#define HD_ENTRYMODE_SHIFT 0x01U |
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#define HD_DISPCTRL 0x08U |
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#define HD_DISPCTRL_ON 0x04U |
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#define HD_DISPCTRL_CURSOR_ON 0x02U |
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#define HD_DISPCTRL_CURSOR_BLINK 0x01U |
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#define HD_CRSR_SHIFT 0x10U |
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#define HD_CRSR_SHIFT_DISPLAY 0x08U |
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#define HD_CRSR_SHIFT_DISPLAY_RIGHT 0x04U |
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#define HD_FUNCSET 0x20U |
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#define HD_FUNCSET_8BIT 0x10U |
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#define HD_FUNCSET_2_LINES 0x08U |
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#define HD_FUNCSET_FONT_5X10 0x04U |
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#define HD_SET_CGRAM 0x40U |
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#define HD_SET_DDRAM 0x80U |
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#define HD_BUSY_FLAG 0x80U |
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/** |
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* struct charlcd - Private data structure |
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* @dev: a pointer back to containing device |
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* @phybase: the offset to the controller in physical memory |
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* @physize: the size of the physical page |
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* @virtbase: the offset to the controller in virtual memory |
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* @irq: reserved interrupt number |
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* @complete: completion structure for the last LCD command |
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* @init_work: delayed work structure to initialize the display on boot |
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*/ |
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struct charlcd { |
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struct device *dev; |
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u32 phybase; |
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u32 physize; |
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void __iomem *virtbase; |
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int irq; |
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struct completion complete; |
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struct delayed_work init_work; |
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}; |
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static irqreturn_t charlcd_interrupt(int irq, void *data) |
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{ |
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struct charlcd *lcd = data; |
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u8 status; |
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status = readl(lcd->virtbase + CHAR_STAT) & 0x01; |
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/* Clear IRQ */ |
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writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); |
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if (status) |
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complete(&lcd->complete); |
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else |
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dev_info(lcd->dev, "Spurious IRQ (%02x)\n", status); |
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return IRQ_HANDLED; |
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} |
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static void charlcd_wait_complete_irq(struct charlcd *lcd) |
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{ |
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int ret; |
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ret = wait_for_completion_interruptible_timeout(&lcd->complete, |
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CHARLCD_TIMEOUT); |
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/* Disable IRQ after completion */ |
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writel(0x00, lcd->virtbase + CHAR_MASK); |
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if (ret < 0) { |
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dev_err(lcd->dev, |
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"wait_for_completion_interruptible_timeout() " |
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"returned %d waiting for ready\n", ret); |
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return; |
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} |
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if (ret == 0) { |
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dev_err(lcd->dev, "charlcd controller timed out " |
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"waiting for ready\n"); |
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return; |
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} |
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} |
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static u8 charlcd_4bit_read_char(struct charlcd *lcd) |
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{ |
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u8 data; |
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u32 val; |
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int i; |
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/* If we can, use an IRQ to wait for the data, else poll */ |
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if (lcd->irq >= 0) |
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charlcd_wait_complete_irq(lcd); |
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else { |
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i = 0; |
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val = 0; |
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while (!(val & CHAR_RAW_VALID) && i < 10) { |
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udelay(100); |
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val = readl(lcd->virtbase + CHAR_RAW); |
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i++; |
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} |
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writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); |
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} |
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msleep(1); |
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/* Read the 4 high bits of the data */ |
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data = readl(lcd->virtbase + CHAR_RD) & 0xf0; |
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/* |
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* The second read for the low bits does not trigger an IRQ |
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* so in this case we have to poll for the 4 lower bits |
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*/ |
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i = 0; |
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val = 0; |
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while (!(val & CHAR_RAW_VALID) && i < 10) { |
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udelay(100); |
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val = readl(lcd->virtbase + CHAR_RAW); |
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i++; |
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} |
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writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); |
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msleep(1); |
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/* Read the 4 low bits of the data */ |
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data |= (readl(lcd->virtbase + CHAR_RD) >> 4) & 0x0f; |
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return data; |
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} |
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static bool charlcd_4bit_read_bf(struct charlcd *lcd) |
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{ |
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if (lcd->irq >= 0) { |
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/* |
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* If we'll use IRQs to wait for the busyflag, clear any |
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* pending flag and enable IRQ |
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*/ |
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writel(CHAR_RAW_CLEAR, lcd->virtbase + CHAR_RAW); |
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init_completion(&lcd->complete); |
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writel(0x01, lcd->virtbase + CHAR_MASK); |
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} |
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readl(lcd->virtbase + CHAR_COM); |
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return charlcd_4bit_read_char(lcd) & HD_BUSY_FLAG ? true : false; |
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} |
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static void charlcd_4bit_wait_busy(struct charlcd *lcd) |
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{ |
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int retries = 50; |
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udelay(100); |
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while (charlcd_4bit_read_bf(lcd) && retries) |
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retries--; |
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if (!retries) |
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dev_err(lcd->dev, "timeout waiting for busyflag\n"); |
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} |
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static void charlcd_4bit_command(struct charlcd *lcd, u8 cmd) |
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{ |
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u32 cmdlo = (cmd << 4) & 0xf0; |
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u32 cmdhi = (cmd & 0xf0); |
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writel(cmdhi, lcd->virtbase + CHAR_COM); |
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udelay(10); |
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writel(cmdlo, lcd->virtbase + CHAR_COM); |
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charlcd_4bit_wait_busy(lcd); |
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} |
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static void charlcd_4bit_char(struct charlcd *lcd, u8 ch) |
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{ |
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u32 chlo = (ch << 4) & 0xf0; |
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u32 chhi = (ch & 0xf0); |
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writel(chhi, lcd->virtbase + CHAR_DAT); |
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udelay(10); |
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writel(chlo, lcd->virtbase + CHAR_DAT); |
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charlcd_4bit_wait_busy(lcd); |
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} |
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static void charlcd_4bit_print(struct charlcd *lcd, int line, const char *str) |
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{ |
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u8 offset; |
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int i; |
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/* |
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* We support line 0, 1 |
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* Line 1 runs from 0x00..0x27 |
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* Line 2 runs from 0x28..0x4f |
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*/ |
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if (line == 0) |
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offset = 0; |
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else if (line == 1) |
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offset = 0x28; |
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else |
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return; |
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/* Set offset */ |
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charlcd_4bit_command(lcd, HD_SET_DDRAM | offset); |
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/* Send string */ |
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for (i = 0; i < strlen(str) && i < 0x28; i++) |
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charlcd_4bit_char(lcd, str[i]); |
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} |
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static void charlcd_4bit_init(struct charlcd *lcd) |
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{ |
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/* These commands cannot be checked with the busy flag */ |
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writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM); |
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msleep(5); |
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writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM); |
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udelay(100); |
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writel(HD_FUNCSET | HD_FUNCSET_8BIT, lcd->virtbase + CHAR_COM); |
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udelay(100); |
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/* Go to 4bit mode */ |
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writel(HD_FUNCSET, lcd->virtbase + CHAR_COM); |
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udelay(100); |
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/* |
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* 4bit mode, 2 lines, 5x8 font, after this the number of lines |
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* and the font cannot be changed until the next initialization sequence |
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*/ |
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charlcd_4bit_command(lcd, HD_FUNCSET | HD_FUNCSET_2_LINES); |
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charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON); |
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charlcd_4bit_command(lcd, HD_ENTRYMODE | HD_ENTRYMODE_INCREMENT); |
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charlcd_4bit_command(lcd, HD_CLEAR); |
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charlcd_4bit_command(lcd, HD_HOME); |
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/* Put something useful in the display */ |
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charlcd_4bit_print(lcd, 0, "ARM Linux"); |
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charlcd_4bit_print(lcd, 1, UTS_RELEASE); |
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} |
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static void charlcd_init_work(struct work_struct *work) |
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{ |
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struct charlcd *lcd = |
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container_of(work, struct charlcd, init_work.work); |
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charlcd_4bit_init(lcd); |
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} |
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static int __init charlcd_probe(struct platform_device *pdev) |
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{ |
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int ret; |
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struct charlcd *lcd; |
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struct resource *res; |
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lcd = kzalloc(sizeof(struct charlcd), GFP_KERNEL); |
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if (!lcd) |
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return -ENOMEM; |
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lcd->dev = &pdev->dev; |
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res = platform_get_resource(pdev, IORESOURCE_MEM, 0); |
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if (!res) { |
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ret = -ENOENT; |
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goto out_no_resource; |
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} |
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lcd->phybase = res->start; |
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lcd->physize = resource_size(res); |
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if (request_mem_region(lcd->phybase, lcd->physize, |
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DRIVERNAME) == NULL) { |
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ret = -EBUSY; |
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goto out_no_memregion; |
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} |
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lcd->virtbase = ioremap(lcd->phybase, lcd->physize); |
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if (!lcd->virtbase) { |
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ret = -ENOMEM; |
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goto out_no_memregion; |
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} |
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lcd->irq = platform_get_irq(pdev, 0); |
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/* If no IRQ is supplied, we'll survive without it */ |
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if (lcd->irq >= 0) { |
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if (request_irq(lcd->irq, charlcd_interrupt, 0, |
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DRIVERNAME, lcd)) { |
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ret = -EIO; |
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goto out_no_irq; |
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} |
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} |
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platform_set_drvdata(pdev, lcd); |
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/* |
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* Initialize the display in a delayed work, because |
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* it is VERY slow and would slow down the boot of the system. |
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*/ |
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INIT_DELAYED_WORK(&lcd->init_work, charlcd_init_work); |
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schedule_delayed_work(&lcd->init_work, 0); |
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dev_info(&pdev->dev, "initialized ARM character LCD at %08x\n", |
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lcd->phybase); |
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return 0; |
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out_no_irq: |
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iounmap(lcd->virtbase); |
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out_no_memregion: |
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release_mem_region(lcd->phybase, SZ_4K); |
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out_no_resource: |
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kfree(lcd); |
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return ret; |
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} |
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static int charlcd_suspend(struct device *dev) |
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{ |
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struct charlcd *lcd = dev_get_drvdata(dev); |
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/* Power the display off */ |
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charlcd_4bit_command(lcd, HD_DISPCTRL); |
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return 0; |
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} |
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static int charlcd_resume(struct device *dev) |
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{ |
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struct charlcd *lcd = dev_get_drvdata(dev); |
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/* Turn the display back on */ |
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charlcd_4bit_command(lcd, HD_DISPCTRL | HD_DISPCTRL_ON); |
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return 0; |
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} |
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static const struct dev_pm_ops charlcd_pm_ops = { |
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.suspend = charlcd_suspend, |
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.resume = charlcd_resume, |
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}; |
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static const struct of_device_id charlcd_match[] = { |
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{ .compatible = "arm,versatile-lcd", }, |
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{} |
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}; |
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static struct platform_driver charlcd_driver = { |
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.driver = { |
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.name = DRIVERNAME, |
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.pm = &charlcd_pm_ops, |
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.suppress_bind_attrs = true, |
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.of_match_table = of_match_ptr(charlcd_match), |
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}, |
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}; |
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builtin_platform_driver_probe(charlcd_driver, charlcd_probe);
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