linux-kernel - Re: [PATCH v7 3/3] pinctrl: nuvoton: Add ma35d1 pinctrl and GPIO driver

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Message-ID: <843c3c2a-2f46-4d49-aed4-ad07ebcb7b27@gmail.com>
Date: Mon, 22 Apr 2024 17:19:15 +0800
From: Jacky Huang <ychuang570808@...il.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: linus.walleij@...aro.org, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 p.zabel@...gutronix.de, j.neuschaefer@....net,
 linux-arm-kernel@...ts.infradead.org, linux-gpio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 ychuang3@...oton.com, schung@...oton.com
Subject: Re: [PATCH v7 3/3] pinctrl: nuvoton: Add ma35d1 pinctrl and GPIO
 driver

Dear Andy,


On 2024/4/22 下午 04:16, Andy Shevchenko wrote:
> On Mon, Apr 22, 2024 at 7:10 AM Jacky Huang <ychuang570808@...il.com> wrote:
>> On 2024/4/10 下午 04:54, Andy Shevchenko wrote:
> ...
>
>>>> +#define MA35_GP_MODE_MASK_WIDTH              2
>>>> +
>>>> +#define MA35_GP_SLEWCTL_MASK_WIDTH   2
>>> I looked at the code how you use these... Oh, please switch to FIELD_GET() /
>>> FIELD_PREP() (don't forget to include bitfield.h)
>>>
>>> ...
>>>
>>> ...
>>>> +             regval &= ~GENMASK(setting->shift + MA35_MFP_BITS_PER_PORT - 1,
>>>> +                                setting->shift);
>>> This will generate an awful code. Use respective FIELD_*() macros.
>>>
>>> ...
>>>
>>>> +     regval &= ~GENMASK(gpio * MA35_GP_MODE_MASK_WIDTH - 1,
>>>> +                        gpio * MA35_GP_MODE_MASK_WIDTH);
>>>> +     regval |= mode << gpio * MA35_GP_MODE_MASK_WIDTH;
>>> Ditto.
>>>
>>> ...
>>>
>>>> +     regval &= GENMASK(gpio * MA35_GP_MODE_MASK_WIDTH - 1,
>>>> +                       gpio * MA35_GP_MODE_MASK_WIDTH);
>>>> +
>>>> +     return regval >> gpio * MA35_GP_MODE_MASK_WIDTH;
>>> Ditto.
> ...
>
>> Allow me to remove irrelevant parts.
>>
>> I attempted to follow your advice and use FIELD_GET() and FIELD_PREP(),
>> but found
>> it impractical. The reason is that these two macros require their 'mask'
>> argument
>> to be a constant, otherwise compilation errors occur, which is the issue
>> I encountered.
>> Since the mask here is calculated and not a constant, compilation errors
>> occur.
>>
>> Taking MA35_GP_REG_MODE as an example, within 32 bits, every 2 bits
>> represent
>> the mode of a GPIO pin, and the mask is obtained by GENMASK(gpio * 2 -1,
>> gpio * 2),
> This is not good for the compiler, it can't figure out (at least in
> some _supported_ by Linux kernel versions on some architectures) that
> GENMASK can be constant here just left-shifted by arbitrary bits.
>
>> where the 'gpio' argument is a variable, not a constant, leading to
>> compilation
>> errors.
>>
>> Due to this reason, I will leave this part unchanged, or do you have any
>> other suggestions?
> If you need non-constant field_get()/field_prep(), add a new patch
> that moves them from drivers/iio/temperature/mlx90614.c (and there are
> more custom implementations:
> https://elixir.bootlin.com/linux/latest/A/ident/field_get) to the
> bitfield.h and use them in your code.
>

Thank you. It works for me. I will adopt the approach used in mlx90614.c.


Best Regards,
Jacky Huang