On Mon, Aug 21, 2017 at 09:31:41PM +0200, Danilo Krummrich wrote:
> This driver provides PS/2 serio bus support by implementing bit banging
> with the GPIO API. The GPIO pins, data and clock, can be configured with
> a node in the device tree or by generic device properties (GDP).
>
> Writing to a device is supported as well, though it is possible timings
> can not be halt as they are tough and difficult to reach with bit banging.
> Therefore it can be configured (also in DT and GDP) whether the serio
> write function should be available for clients.
>
> This driver is for development purposes and not recommended for productive
> use. However, this driver can be useful e.g. when no USB port is available
> or using old peripherals is desired as PS/2 controller chips getting rare.
>
> This driver was tested on bcm2825 and on Kirin 960 and it worked well
> together with the atkbd and psmouse driver.
>
> Signed-off-by: Danilo Krummrich <danilokrummrich@xxxxxxxxxxxxx>
Applied, thank you.
> ---
> Documentation/gpio/drivers-on-gpio.txt | 5 +
> drivers/input/serio/Kconfig | 11 +
> drivers/input/serio/Makefile | 1 +
> drivers/input/serio/ps2-gpio.c | 453 +++++++++++++++++++++++++++++++++
> 4 files changed, 470 insertions(+)
> create mode 100644 drivers/input/serio/ps2-gpio.c
>
> diff --git a/Documentation/gpio/drivers-on-gpio.txt b/Documentation/gpio/drivers-on-gpio.txt
> index 306513251713..9a78d385b92e 100644
> --- a/Documentation/gpio/drivers-on-gpio.txt
> +++ b/Documentation/gpio/drivers-on-gpio.txt
> @@ -84,6 +84,11 @@ hardware descriptions such as device tree or ACPI:
> NAND flash MTD subsystem and provides chip access and partition parsing like
> any other NAND driving hardware.
>
> +- ps2-gpio: drivers/input/serio/ps2-gpio.c is used to drive a PS/2 (IBM) serio
> + bus, data and clock line, by bit banging two GPIO lines. It will appear as
> + any other serio bus to the system and makes it possible to connect drivers
> + for e.g. keyboards and other PS/2 protocol based devices.
> +
> Apart from this there are special GPIO drivers in subsystems like MMC/SD to
> read card detect and write protect GPIO lines, and in the TTY serial subsystem
> to emulate MCTRL (modem control) signals CTS/RTS by using two GPIO lines. The
> diff --git a/drivers/input/serio/Kconfig b/drivers/input/serio/Kconfig
> index c3d05b4d3118..21488c048fa3 100644
> --- a/drivers/input/serio/Kconfig
> +++ b/drivers/input/serio/Kconfig
> @@ -292,6 +292,17 @@ config SERIO_SUN4I_PS2
> To compile this driver as a module, choose M here: the
> module will be called sun4i-ps2.
>
> +config SERIO_GPIO_PS2
> + tristate "GPIO PS/2 bit banging driver"
> + depends on GPIOLIB
> + help
> + Say Y here if you want PS/2 bit banging support via GPIO.
> +
> + To compile this driver as a module, choose M here: the
> + module will be called ps2-gpio.
> +
> + If you are unsure, say N.
> +
> config USERIO
> tristate "User space serio port driver support"
> help
> diff --git a/drivers/input/serio/Makefile b/drivers/input/serio/Makefile
> index 2374ef9b33d7..767bd9b6e1ed 100644
> --- a/drivers/input/serio/Makefile
> +++ b/drivers/input/serio/Makefile
> @@ -30,4 +30,5 @@ obj-$(CONFIG_SERIO_APBPS2) += apbps2.o
> obj-$(CONFIG_SERIO_OLPC_APSP) += olpc_apsp.o
> obj-$(CONFIG_HYPERV_KEYBOARD) += hyperv-keyboard.o
> obj-$(CONFIG_SERIO_SUN4I_PS2) += sun4i-ps2.o
> +obj-$(CONFIG_SERIO_GPIO_PS2) += ps2-gpio.o
> obj-$(CONFIG_USERIO) += userio.o
> diff --git a/drivers/input/serio/ps2-gpio.c b/drivers/input/serio/ps2-gpio.c
> new file mode 100644
> index 000000000000..b50e3817f3c4
> --- /dev/null
> +++ b/drivers/input/serio/ps2-gpio.c
> @@ -0,0 +1,453 @@
> +/*
> + * GPIO based serio bus driver for bit banging the PS/2 protocol
> + *
> + * Author: Danilo Krummrich <danilokrummrich@xxxxxxxxxxxxx>
> + *
> + * 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@xxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("GPIO PS2 driver");
> +MODULE_LICENSE("GPL v2");
> --
> 2.14.1
>
--
Dmitry
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