Re: [PATCH v5] serio: PS/2 gpio bit banging driver for serio bus
From: Antonio Borneo
Date: Thu Aug 03 2017 - 12:16:05 EST
Hi Danilo,
just two minor issues below
On Thu, Aug 3, 2017 at 5:43 PM, Danilo Krummrich
<danilokrummrich@xxxxxxxxxxxxx> 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 RPI1 and on Hikey960 and it worked well together
> with the atkbd and psmouse driver.
>
> Signed-off-by: Danilo Krummrich <danilokrummrich@xxxxxxxxxxxxx>
> ---
> v2: Removed one verbose print statement, changed another one to dev_dbg.
> v3: - fixed compiler warning on blackfin
> - depends on GPIOLIB
> - clarify documentation
> v4: - fixed concurrent calls to ps2_gpio_write (serio->write)
> - use gpiod API
> - use generic device properties
> - request irq separately, do not use gpiod_to_irq
> - abort when gpio is connected via slow bus
> - Fixed a bug where PS2_CMD_RESEND is always send after tx failed once.
> The makes the write functionallity work better, tough timing is still
> critical.
> - disable irq initially until ps2_gpip_open (serio->open) is called
> v5: Checked again why timings are that hard to reach while in tx mode and
> discovered that there is an extra clock pulse between stop bit sent from
> host and acknowledgement from device. By just skipping this clock pulse
> tx works fine now, though it still happens sometimes that the timing can
> not be reached of course.
> ---
> .../devicetree/bindings/serio/ps2-gpio.txt | 22 +
> Documentation/gpio/drivers-on-gpio.txt | 5 +
> drivers/input/serio/Kconfig | 11 +
> drivers/input/serio/Makefile | 1 +
> drivers/input/serio/ps2-gpio.c | 456 +++++++++++++++++++++
> 5 files changed, 495 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/serio/ps2-gpio.txt
> create mode 100644 drivers/input/serio/ps2-gpio.c
>
> diff --git a/Documentation/devicetree/bindings/serio/ps2-gpio.txt b/Documentation/devicetree/bindings/serio/ps2-gpio.txt
> new file mode 100644
> index 0000000..19d42ca
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/serio/ps2-gpio.txt
> @@ -0,0 +1,22 @@
> +Device-Tree bindings for ps2 gpio driver
> +
> +Required properties:
> + - compatible = "ps2-gpio"
> + - gpios: data and clock gpio
> + - interrupts: Should trigger on the falling edge of the clock line.
> +
> +Optional properties:
> + - ps2-gpio,write-enable: Indicates whether write function is provided
> + to serio device. Possibly providing the write fn will not work, because
> + of the tough timing requirements.
> +
> +Example nodes:
> +
> +ps2@0 {
> + compatible = "ps2-gpio";
> + interrupt-parent = <&gpio>;
> + interrupts = <23 IRQ_TYPE_EDGE_FALLING>;
> + data-gpios = <&gpio 24 GPIO_ACTIVE_HIGH>;
> + clk-gpios = <&gpio 23 GPIO_ACTIVE_HIGH>;
> + ps2-gpio,write-enable;
> +};
> diff --git a/Documentation/gpio/drivers-on-gpio.txt b/Documentation/gpio/drivers-on-gpio.txt
> index 3065132..97c8716 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 an PS/2 (IBM) serio
Should be "a PS/2"
> + 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 c3d05b4..292d6e2 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 gpio-ps2.
I think it is called ps2-gpio.
Regars,
Antonio