[PATCH] serio: PS/2 gpio bit banging driver for serio bus

2017-08-11 Thread Danilo Krummrich 
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 
---
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.
v6: - fixed typos
- use of_match_ptr
v7: remove unnecessary barriers
---
 .../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 | 453 +
 5 files changed, 492 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 ..099dd6d46cb3
--- /dev/null
+++ b/Documentation/devicetree/bindings/serio/ps2-gpio.txt
@@ -0,0 +1,22 @@
+Device-Tree bindings for ps/2 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 = <>;
+   interrupts = <23 IRQ_TYPE_EDGE_FALLING>;
+   data-gpios = < 24 GPIO_ACTIVE_HIGH>;
+   clk-gpios = < 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 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

[PATCH] serio: PS/2 gpio bit banging driver for serio bus

2017-08-11 Thread Danilo Krummrich 
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 
---
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.
v6: - fixed typos
- use of_match_ptr
v7: remove unnecessary barriers
---
 .../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 | 453 +
 5 files changed, 492 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 ..099dd6d46cb3
--- /dev/null
+++ b/Documentation/devicetree/bindings/serio/ps2-gpio.txt
@@ -0,0 +1,22 @@
+Device-Tree bindings for ps/2 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 = <>;
+   interrupts = <23 IRQ_TYPE_EDGE_FALLING>;
+   data-gpios = < 24 GPIO_ACTIVE_HIGH>;
+   clk-gpios = < 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 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