linux-kernel - Re: [PATCH v2] pinctrl: pinctrl-single: Fix pcs_request_gpio() when bits_per

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Date:   Mon, 5 Mar 2018 16:39:51 -0600
From:   David Lechner <david@...hnology.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tony Lindgren <tony@...mide.com>,
        Haojian Zhuang <haojian.zhuang@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH v2] pinctrl: pinctrl-single: Fix pcs_request_gpio() when
 bits_per_mux != 0

On 02/20/2018 06:56 AM, Andy Shevchenko wrote:
> On Mon, Feb 19, 2018 at 11:57 PM, David Lechner <david@...hnology.com> wrote:
>> This fixes pcs_request_gpio() in the pinctrl-single driver when
>> bits_per_mux != 0. It appears this was overlooked when the multiple
>> pins per register feature was added.
>>
>> Fixes: 4e7e8017a80e ("pinctrl: pinctrl-single: enhance to configure multiple pins of different modules")
>> Signed-off-by: David Lechner <david@...hnology.com>
>> ---
>>
>> v2 changes:
>> - don't wrap Fixes: line in commit message since it is a special machine-
>>    readable line.
>>
>> There was some discussion in v1 about using DIV_ROUND_UP(), etc. macros, but
>> the consensus was to leave it as-is since it matches existing code and that
>> macros can be introduced in another patch.
>>
>>   drivers/pinctrl/pinctrl-single.c | 22 +++++++++++++++++++---
>>   1 file changed, 19 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pinctrl/pinctrl-single.c b/drivers/pinctrl/pinctrl-single.c
>> index cec7537..a7c5eb3 100644
>> --- a/drivers/pinctrl/pinctrl-single.c
>> +++ b/drivers/pinctrl/pinctrl-single.c
>> @@ -391,9 +391,25 @@ static int pcs_request_gpio(struct pinctrl_dev *pctldev,
>>                          || pin < frange->offset)
>>                          continue;
> 
>>                  mux_bytes = pcs->width / BITS_PER_BYTE;
>> -               data = pcs->read(pcs->base + pin * mux_bytes) & ~pcs->fmask;
>> -               data |= frange->gpiofunc;
>> -               pcs->write(data, pcs->base + pin * mux_bytes);
>> +
>> +               if (pcs->bits_per_mux) {
>> +                       int byte_num, offset, pin_shift;
>> +
>> +                       byte_num = (pcs->bits_per_pin * pin) / BITS_PER_BYTE;
>> +                       offset = (byte_num / mux_bytes) * mux_bytes;
>> +                       pin_shift = pin % (pcs->width / pcs->bits_per_pin) *
>> +                                   pcs->bits_per_pin;
>> +
>> +                       data = pcs->read(pcs->base + offset);
>> +                       data &= ~(pcs->fmask << pin_shift);
>> +                       data |= frange->gpiofunc << pin_shift;
>> +                       pcs->write(data, pcs->base + offset);
>> +               } else {
> 
>> +                       data = pcs->read(pcs->base + pin * mux_bytes);
>> +                       data &= ~pcs->fmask;
>> +                       data |= frange->gpiofunc;
>> +                       pcs->write(data, pcs->base + pin * mux_bytes);
> 
> Just an idea, you may leave this almost untouched and do calculate
> pin_shift and offset in condition, like
> 
> if (...) {
>   pin_shift = ...
>   offset = ...
> } else {
>   pin_shift = 0;
>   offset = pin * mux_bytes;
> }
> 
>                         data = pcs->read(pcs->base + offset);
>                         data &= ~(pcs->fmask << pin_shift);
>                         data |= frange->gpiofunc << pin_shift;
>                         pcs->write(data, pcs->base + offset);
> 
> It's also possible to split to two changes, where first introduces
> that variables and their default values (see 'else' branch) and second
> one introduces an if branch override.
> 
>> +               }
>>                  break;
> 

Yes, there are many ways this could be done. However, I would like
to just leave it as it is since it matches the patterns used
elsewhere in this file.