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

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Message-ID: <5893a5a264436ec720dbe977fad37105@dk-develop.de>
Date:   Thu, 17 Aug 2017 18:13:01 +0200
From:   Danilo Krummrich <danilokrummrich@...develop.de>
To:     Rob Herring <robh@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        dmitry.torokhov@...il.com, linus.walleij@...aro.org,
        rdunlap@...radead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v7] serio: PS/2 gpio bit banging driver for serio bus

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@...develop.de>
>> ---
>> 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