diff options
Diffstat (limited to 'drivers/input/serio/ps2-gpio.c')
| -rw-r--r-- | drivers/input/serio/ps2-gpio.c | 450 |
1 files changed, 450 insertions, 0 deletions
diff --git a/drivers/input/serio/ps2-gpio.c b/drivers/input/serio/ps2-gpio.c new file mode 100644 index 000000000..8970b49ea --- /dev/null +++ b/drivers/input/serio/ps2-gpio.c @@ -0,0 +1,450 @@ +// 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"); |