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450 lines
10 KiB
450 lines
10 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* GPIO based serio bus driver for bit banging the PS/2 protocol |
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* |
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* Author: Danilo Krummrich <[email protected]> |
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*/ |
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#include <linux/gpio/consumer.h> |
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#include <linux/interrupt.h> |
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#include <linux/module.h> |
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#include <linux/serio.h> |
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#include <linux/slab.h> |
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#include <linux/platform_device.h> |
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#include <linux/workqueue.h> |
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#include <linux/completion.h> |
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#include <linux/mutex.h> |
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#include <linux/preempt.h> |
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#include <linux/property.h> |
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#include <linux/of.h> |
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#include <linux/jiffies.h> |
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#include <linux/delay.h> |
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#define DRIVER_NAME "ps2-gpio" |
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#define PS2_MODE_RX 0 |
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#define PS2_MODE_TX 1 |
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#define PS2_START_BIT 0 |
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#define PS2_DATA_BIT0 1 |
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#define PS2_DATA_BIT1 2 |
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#define PS2_DATA_BIT2 3 |
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#define PS2_DATA_BIT3 4 |
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#define PS2_DATA_BIT4 5 |
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#define PS2_DATA_BIT5 6 |
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#define PS2_DATA_BIT6 7 |
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#define PS2_DATA_BIT7 8 |
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#define PS2_PARITY_BIT 9 |
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#define PS2_STOP_BIT 10 |
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#define PS2_TX_TIMEOUT 11 |
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#define PS2_ACK_BIT 12 |
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#define PS2_DEV_RET_ACK 0xfa |
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#define PS2_DEV_RET_NACK 0xfe |
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#define PS2_CMD_RESEND 0xfe |
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struct ps2_gpio_data { |
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struct device *dev; |
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struct serio *serio; |
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unsigned char mode; |
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struct gpio_desc *gpio_clk; |
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struct gpio_desc *gpio_data; |
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bool write_enable; |
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int irq; |
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unsigned char rx_cnt; |
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unsigned char rx_byte; |
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unsigned char tx_cnt; |
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unsigned char tx_byte; |
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struct completion tx_done; |
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struct mutex tx_mutex; |
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struct delayed_work tx_work; |
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}; |
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static int ps2_gpio_open(struct serio *serio) |
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{ |
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struct ps2_gpio_data *drvdata = serio->port_data; |
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enable_irq(drvdata->irq); |
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return 0; |
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} |
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static void ps2_gpio_close(struct serio *serio) |
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{ |
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struct ps2_gpio_data *drvdata = serio->port_data; |
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flush_delayed_work(&drvdata->tx_work); |
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disable_irq(drvdata->irq); |
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} |
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static int __ps2_gpio_write(struct serio *serio, unsigned char val) |
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{ |
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struct ps2_gpio_data *drvdata = serio->port_data; |
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disable_irq_nosync(drvdata->irq); |
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gpiod_direction_output(drvdata->gpio_clk, 0); |
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drvdata->mode = PS2_MODE_TX; |
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drvdata->tx_byte = val; |
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schedule_delayed_work(&drvdata->tx_work, usecs_to_jiffies(200)); |
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return 0; |
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} |
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static int ps2_gpio_write(struct serio *serio, unsigned char val) |
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{ |
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struct ps2_gpio_data *drvdata = serio->port_data; |
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int ret = 0; |
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if (in_task()) { |
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mutex_lock(&drvdata->tx_mutex); |
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__ps2_gpio_write(serio, val); |
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if (!wait_for_completion_timeout(&drvdata->tx_done, |
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msecs_to_jiffies(10000))) |
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ret = SERIO_TIMEOUT; |
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mutex_unlock(&drvdata->tx_mutex); |
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} else { |
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__ps2_gpio_write(serio, val); |
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} |
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return ret; |
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} |
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static void ps2_gpio_tx_work_fn(struct work_struct *work) |
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{ |
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struct delayed_work *dwork = to_delayed_work(work); |
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struct ps2_gpio_data *drvdata = container_of(dwork, |
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struct ps2_gpio_data, |
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tx_work); |
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enable_irq(drvdata->irq); |
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gpiod_direction_output(drvdata->gpio_data, 0); |
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gpiod_direction_input(drvdata->gpio_clk); |
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} |
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static irqreturn_t ps2_gpio_irq_rx(struct ps2_gpio_data *drvdata) |
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{ |
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unsigned char byte, cnt; |
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int data; |
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int rxflags = 0; |
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static unsigned long old_jiffies; |
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byte = drvdata->rx_byte; |
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cnt = drvdata->rx_cnt; |
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if (old_jiffies == 0) |
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old_jiffies = jiffies; |
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if ((jiffies - old_jiffies) > usecs_to_jiffies(100)) { |
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dev_err(drvdata->dev, |
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"RX: timeout, probably we missed an interrupt\n"); |
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goto err; |
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} |
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old_jiffies = jiffies; |
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data = gpiod_get_value(drvdata->gpio_data); |
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if (unlikely(data < 0)) { |
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dev_err(drvdata->dev, "RX: failed to get data gpio val: %d\n", |
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data); |
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goto err; |
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} |
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switch (cnt) { |
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case PS2_START_BIT: |
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/* start bit should be low */ |
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if (unlikely(data)) { |
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dev_err(drvdata->dev, "RX: start bit should be low\n"); |
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goto err; |
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} |
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break; |
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case PS2_DATA_BIT0: |
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case PS2_DATA_BIT1: |
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case PS2_DATA_BIT2: |
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case PS2_DATA_BIT3: |
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case PS2_DATA_BIT4: |
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case PS2_DATA_BIT5: |
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case PS2_DATA_BIT6: |
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case PS2_DATA_BIT7: |
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/* processing data bits */ |
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if (data) |
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byte |= (data << (cnt - 1)); |
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break; |
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case PS2_PARITY_BIT: |
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/* check odd parity */ |
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if (!((hweight8(byte) & 1) ^ data)) { |
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rxflags |= SERIO_PARITY; |
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dev_warn(drvdata->dev, "RX: parity error\n"); |
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if (!drvdata->write_enable) |
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goto err; |
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} |
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/* Do not send spurious ACK's and NACK's when write fn is |
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* not provided. |
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*/ |
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if (!drvdata->write_enable) { |
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if (byte == PS2_DEV_RET_NACK) |
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goto err; |
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else if (byte == PS2_DEV_RET_ACK) |
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break; |
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} |
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/* Let's send the data without waiting for the stop bit to be |
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* sent. It may happen that we miss the stop bit. When this |
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* happens we have no way to recover from this, certainly |
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* missing the parity bit would be recognized when processing |
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* the stop bit. When missing both, data is lost. |
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*/ |
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serio_interrupt(drvdata->serio, byte, rxflags); |
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dev_dbg(drvdata->dev, "RX: sending byte 0x%x\n", byte); |
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break; |
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case PS2_STOP_BIT: |
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/* stop bit should be high */ |
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if (unlikely(!data)) { |
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dev_err(drvdata->dev, "RX: stop bit should be high\n"); |
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goto err; |
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} |
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cnt = byte = 0; |
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old_jiffies = 0; |
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goto end; /* success */ |
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default: |
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dev_err(drvdata->dev, "RX: got out of sync with the device\n"); |
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goto err; |
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} |
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cnt++; |
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goto end; /* success */ |
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err: |
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cnt = byte = 0; |
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old_jiffies = 0; |
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__ps2_gpio_write(drvdata->serio, PS2_CMD_RESEND); |
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end: |
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drvdata->rx_cnt = cnt; |
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drvdata->rx_byte = byte; |
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return IRQ_HANDLED; |
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} |
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static irqreturn_t ps2_gpio_irq_tx(struct ps2_gpio_data *drvdata) |
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{ |
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unsigned char byte, cnt; |
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int data; |
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static unsigned long old_jiffies; |
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cnt = drvdata->tx_cnt; |
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byte = drvdata->tx_byte; |
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if (old_jiffies == 0) |
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old_jiffies = jiffies; |
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if ((jiffies - old_jiffies) > usecs_to_jiffies(100)) { |
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dev_err(drvdata->dev, |
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"TX: timeout, probably we missed an interrupt\n"); |
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goto err; |
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} |
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old_jiffies = jiffies; |
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switch (cnt) { |
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case PS2_START_BIT: |
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/* should never happen */ |
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dev_err(drvdata->dev, |
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"TX: start bit should have been sent already\n"); |
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goto err; |
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case PS2_DATA_BIT0: |
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case PS2_DATA_BIT1: |
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case PS2_DATA_BIT2: |
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case PS2_DATA_BIT3: |
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case PS2_DATA_BIT4: |
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case PS2_DATA_BIT5: |
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case PS2_DATA_BIT6: |
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case PS2_DATA_BIT7: |
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data = byte & BIT(cnt - 1); |
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gpiod_set_value(drvdata->gpio_data, data); |
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break; |
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case PS2_PARITY_BIT: |
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/* do odd parity */ |
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data = !(hweight8(byte) & 1); |
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gpiod_set_value(drvdata->gpio_data, data); |
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break; |
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case PS2_STOP_BIT: |
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/* release data line to generate stop bit */ |
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gpiod_direction_input(drvdata->gpio_data); |
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break; |
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case PS2_TX_TIMEOUT: |
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/* Devices generate one extra clock pulse before sending the |
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* acknowledgment. |
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*/ |
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break; |
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case PS2_ACK_BIT: |
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gpiod_direction_input(drvdata->gpio_data); |
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data = gpiod_get_value(drvdata->gpio_data); |
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if (data) { |
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dev_warn(drvdata->dev, "TX: received NACK, retry\n"); |
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goto err; |
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} |
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drvdata->mode = PS2_MODE_RX; |
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complete(&drvdata->tx_done); |
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cnt = 1; |
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old_jiffies = 0; |
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goto end; /* success */ |
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default: |
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/* Probably we missed the stop bit. Therefore we release data |
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* line and try again. |
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*/ |
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gpiod_direction_input(drvdata->gpio_data); |
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dev_err(drvdata->dev, "TX: got out of sync with the device\n"); |
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goto err; |
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} |
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cnt++; |
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goto end; /* success */ |
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err: |
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cnt = 1; |
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old_jiffies = 0; |
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gpiod_direction_input(drvdata->gpio_data); |
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__ps2_gpio_write(drvdata->serio, drvdata->tx_byte); |
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end: |
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drvdata->tx_cnt = cnt; |
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return IRQ_HANDLED; |
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} |
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static irqreturn_t ps2_gpio_irq(int irq, void *dev_id) |
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{ |
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struct ps2_gpio_data *drvdata = dev_id; |
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return drvdata->mode ? ps2_gpio_irq_tx(drvdata) : |
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ps2_gpio_irq_rx(drvdata); |
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} |
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static int ps2_gpio_get_props(struct device *dev, |
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struct ps2_gpio_data *drvdata) |
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{ |
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drvdata->gpio_data = devm_gpiod_get(dev, "data", GPIOD_IN); |
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if (IS_ERR(drvdata->gpio_data)) { |
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dev_err(dev, "failed to request data gpio: %ld", |
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PTR_ERR(drvdata->gpio_data)); |
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return PTR_ERR(drvdata->gpio_data); |
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} |
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drvdata->gpio_clk = devm_gpiod_get(dev, "clk", GPIOD_IN); |
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if (IS_ERR(drvdata->gpio_clk)) { |
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dev_err(dev, "failed to request clock gpio: %ld", |
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PTR_ERR(drvdata->gpio_clk)); |
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return PTR_ERR(drvdata->gpio_clk); |
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} |
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drvdata->write_enable = device_property_read_bool(dev, |
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"write-enable"); |
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return 0; |
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} |
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static int ps2_gpio_probe(struct platform_device *pdev) |
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{ |
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struct ps2_gpio_data *drvdata; |
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struct serio *serio; |
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struct device *dev = &pdev->dev; |
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int error; |
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drvdata = devm_kzalloc(dev, sizeof(struct ps2_gpio_data), GFP_KERNEL); |
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serio = kzalloc(sizeof(struct serio), GFP_KERNEL); |
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if (!drvdata || !serio) { |
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error = -ENOMEM; |
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goto err_free_serio; |
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} |
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error = ps2_gpio_get_props(dev, drvdata); |
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if (error) |
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goto err_free_serio; |
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if (gpiod_cansleep(drvdata->gpio_data) || |
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gpiod_cansleep(drvdata->gpio_clk)) { |
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dev_err(dev, "GPIO data or clk are connected via slow bus\n"); |
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error = -EINVAL; |
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goto err_free_serio; |
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} |
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drvdata->irq = platform_get_irq(pdev, 0); |
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if (drvdata->irq < 0) { |
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error = drvdata->irq; |
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goto err_free_serio; |
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} |
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error = devm_request_irq(dev, drvdata->irq, ps2_gpio_irq, |
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IRQF_NO_THREAD, DRIVER_NAME, drvdata); |
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if (error) { |
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dev_err(dev, "failed to request irq %d: %d\n", |
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drvdata->irq, error); |
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goto err_free_serio; |
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} |
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/* Keep irq disabled until serio->open is called. */ |
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disable_irq(drvdata->irq); |
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serio->id.type = SERIO_8042; |
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serio->open = ps2_gpio_open; |
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serio->close = ps2_gpio_close; |
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/* Write can be enabled in platform/dt data, but possibly it will not |
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* work because of the tough timings. |
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*/ |
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serio->write = drvdata->write_enable ? ps2_gpio_write : NULL; |
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serio->port_data = drvdata; |
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serio->dev.parent = dev; |
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strlcpy(serio->name, dev_name(dev), sizeof(serio->name)); |
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strlcpy(serio->phys, dev_name(dev), sizeof(serio->phys)); |
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drvdata->serio = serio; |
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drvdata->dev = dev; |
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drvdata->mode = PS2_MODE_RX; |
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/* Tx count always starts at 1, as the start bit is sent implicitly by |
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* host-to-device communication initialization. |
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*/ |
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drvdata->tx_cnt = 1; |
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INIT_DELAYED_WORK(&drvdata->tx_work, ps2_gpio_tx_work_fn); |
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init_completion(&drvdata->tx_done); |
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mutex_init(&drvdata->tx_mutex); |
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serio_register_port(serio); |
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platform_set_drvdata(pdev, drvdata); |
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return 0; /* success */ |
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err_free_serio: |
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kfree(serio); |
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return error; |
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} |
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static int ps2_gpio_remove(struct platform_device *pdev) |
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{ |
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struct ps2_gpio_data *drvdata = platform_get_drvdata(pdev); |
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serio_unregister_port(drvdata->serio); |
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return 0; |
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} |
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#if defined(CONFIG_OF) |
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static const struct of_device_id ps2_gpio_match[] = { |
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{ .compatible = "ps2-gpio", }, |
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{ }, |
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}; |
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MODULE_DEVICE_TABLE(of, ps2_gpio_match); |
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#endif |
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static struct platform_driver ps2_gpio_driver = { |
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.probe = ps2_gpio_probe, |
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.remove = ps2_gpio_remove, |
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.driver = { |
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.name = DRIVER_NAME, |
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.of_match_table = of_match_ptr(ps2_gpio_match), |
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}, |
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}; |
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module_platform_driver(ps2_gpio_driver); |
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MODULE_AUTHOR("Danilo Krummrich <[email protected]>"); |
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MODULE_DESCRIPTION("GPIO PS2 driver"); |
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MODULE_LICENSE("GPL v2");
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