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