451 lines
10 KiB
C
451 lines
10 KiB
C
// 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 <danilokrummrich@dk-develop.de>
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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 <danilokrummrich@dk-develop.de>");
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MODULE_DESCRIPTION("GPIO PS2 driver");
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MODULE_LICENSE("GPL v2");
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