--- /dev/null
+/*
+ * GPIO based serio bus driver for bit banging the PS/2 protocol
+ *
+ * Author: Danilo Krummrich <danilokrummrich@dk-develop.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#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;
+
+ 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;
+ }
+
+ drvdata->irq = platform_get_irq(pdev, 0);
+ if (drvdata->irq < 0) {
+ dev_err(dev, "failed to get irq from platform resource: %d\n",
+ drvdata->irq);
+ 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");
projects / users / willy / pagecache.git / commitdiff