Re: [PATCH v7] serio: PS/2 gpio bit banging driver for serio bus

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Hi Bob,

thanks for reviewing.

On 2017-08-17 17:43, Rob Herring wrote:
On Fri, Aug 11, 2017 at 03:17:36PM +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 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.
v6: - fixed typos
    - use of_match_ptr
v7: remove unnecessary barriers

Sorry for resending, forgot der version tag in the subject.
---
 .../devicetree/bindings/serio/ps2-gpio.txt         |  22 +

It's preferred to split bindings to separate patch.

Together with Documentation/gpio/drivers-on-gpio.txt or would you prefer to have
a separate patch for this as well?
 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 000000000000..099dd6d46cb3
--- /dev/null
+++ b/Documentation/devicetree/bindings/serio/ps2-gpio.txt
@@ -0,0 +1,22 @@
+Device-Tree bindings for ps/2 gpio driver

Bindings don't describe drivers.

Will fix.
+
+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

ps2-gpio is not a vendor prefix, so drop it.

I will do.
+ 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;
+};

Thanks,
Danilo
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