linux-kernel - Re: [PATCH v6 1/8] MFD: add bindings for STM32 Timers driver

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Date:   Tue, 13 Dec 2016 15:07:14 -0600
From:   Rob Herring <robh@...nel.org>
To:     Benjamin Gaignard <benjamin.gaignard@...aro.org>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Linux PWM List <linux-pwm@...r.kernel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Fabrice Gasnier <fabrice.gasnier@...com>,
        Gerald Baeza <gerald.baeza@...com>,
        Arnaud Pouliquen <arnaud.pouliquen@...com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
        Benjamin Gaignard <benjamin.gaignard@...com>
Subject: Re: [PATCH v6 1/8] MFD: add bindings for STM32 Timers driver

On Tue, Dec 13, 2016 at 3:29 AM, Benjamin Gaignard
<benjamin.gaignard@...aro.org> wrote:
> 2016-12-12 19:51 GMT+01:00 Rob Herring <robh@...nel.org>:
>> On Fri, Dec 09, 2016 at 03:15:12PM +0100, Benjamin Gaignard wrote:
>>> Add bindings information for STM32 Timers
>>>
>>> version 6:
>>> - rename stm32-gtimer to stm32-timers
>>> - change compatible
>>> - add description about the IPs
>>>
>>> version 2:
>>> - rename stm32-mfd-timer to stm32-gptimer
>>> - only keep one compatible string
>>>
>>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...com>
>>> ---
>>>  .../devicetree/bindings/mfd/stm32-timers.txt       | 46 ++++++++++++++++++++++
>>>  1 file changed, 46 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/mfd/stm32-timers.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/mfd/stm32-timers.txt b/Documentation/devicetree/bindings/mfd/stm32-timers.txt
>>> new file mode 100644
>>> index 0000000..b30868e
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/mfd/stm32-timers.txt
>>> @@ -0,0 +1,46 @@
>>> +STM32 Timers driver bindings
>>> +
>>> +This IP provides 3 types of timer along with PWM functionality:
>>> +- advanced-control timers consist of a 16-bit auto-reload counter driven by a programmable
>>> +  prescaler, break input feature, PWM outputs and complementary PWM ouputs channels.
>>> +- general-purpose timers consist of a 16-bit or 32-bit auto-reload counter driven by a
>>> +  programmable prescaler and PWM outputs.
>>> +- basic timers consist of a 16-bit auto-reload counter driven by a programmable prescaler.
>>> +
>>> +Required parameters:
>>> +- compatible: must be "st,stm32-timers"
>>> +
>>> +- reg:                       Physical base address and length of the controller's
>>> +                     registers.
>>> +- clock-names:               Set to "clk_int".
>>
>> 'clk' is redundant. Also, you don't really need -names when there is
>> only one of them.
>
> I use devm_regmap_init_mmio_clk() which get the clock by it name so
> I have to define it in DT.

Are you sure NULL is not allowed? I don't know, but at least clk_get()
allows NULL.

It's fine to keep, just drop the "clk_" part.

>
>>> +- clocks:            Phandle to the clock used by the timer module.
>>> +                     For Clk properties, please refer to ../clock/clock-bindings.txt
>>> +
>>> +Optional parameters:
>>> +- resets:            Phandle to the parent reset controller.
>>> +                     See ../reset/st,stm32-rcc.txt
>>> +
>>> +Optional subnodes:
>>> +- pwm:                       See ../pwm/pwm-stm32.txt
>>> +- timer:             See ../iio/timer/stm32-timer-trigger.txt
>>> +
>>> +Example:
>>> +     timers@...10000 {
>>> +             #address-cells = <1>;
>>> +             #size-cells = <0>;
>>> +             compatible = "st,stm32-timers";
>>> +             reg = <0x40010000 0x400>;
>>> +             clocks = <&rcc 0 160>;
>>> +             clock-names = "clk_int";
>>> +
>>> +             pwm {
>>> +                     compatible = "st,stm32-pwm";
>>> +                     pinctrl-0       = <&pwm1_pins>;
>>> +                     pinctrl-names   = "default";
>>> +             };
>>> +
>>> +             timer {
>>> +                     compatible = "st,stm32-timer-trigger";
>>> +                     reg = <0>;
>>
>> You don't need reg here as there is only one. In turn, you don't need
>> #address-cells or #size-cells.
>
> I use "reg" to set each timer configuration.
> From hardware point of view they are all the same except for which hardware
> signals they could consume and/or send.

This sounds okay, but...

> "reg" is used as index of the two tables in driver code.

this statement doesn't really sound like valid use of reg.

If you keep reg, then the node needs a unit address (timer@0).

Rob