linux-kernel - Re: [PATCH] mmc: dw_mmc: No bus setup if default pinctrl is used

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Date:	Fri, 8 Feb 2013 04:49:48 +0900
From:	Dongjin Kim <tobetter@...il.com>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	Thomas Abraham <thomas.ab@...sung.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Chris Ball <cjb@...top.org>, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: dw_mmc: No bus setup if default pinctrl is used

Hi Linus,

Thank you for reviewing.

Initially I also considered to use IS_ENABLED(CONFIG_PINCTRL) and
ignore for-block according to its status. But it would make a certain
board failed if gpios is used for pin configuration rather than
default-pinctrl even if CONFIG_PINCTRL is enabled. Also considered to
add a function on pinctrl.c to return if default-pinctrl is used, and
drop down the for-block according to its status. It could replace the
long and complicaed line, IS_ERR(host->dev->pins->default_state), to
simple one as well. :)

The best is obviously to enable CONFIG_PINCTRL and remove the
for-block, it makes the code more simple. I like to have a comment
from Thomas if have to support both cases, gpios and default-pinctrl.

Best regards,
Dongjin.

On Fri, Feb 8, 2013 at 4:03 AM, Linus Walleij <linus.walleij@...aro.org> wrote:
> On Thu, Feb 7, 2013 at 7:17 PM, Dongjin Kim <tobetter@...il.com> wrote:
>
>> Legacy gpio based bus setup is failed when the bus pins are listed with the
>> property 'pinctrl-0' and 'pinctrl-names', instead of 'gpios'. The default
>> pinctrls are handled by device core before probe, no need to configure the
>> pins again in a device driver.
>
> Aha.
>
>>  {
>>         int idx, gpio, ret;
>> +       int nr_pins = NUM_PINS(bus_width);
>>
>>         if (!slot_np)
>>                 return -EINVAL;
>>
>> +#if defined(CONFIG_PINCTRL)
>> +       /* Default pinctrl is used */
>> +       if (!IS_ERR(host->dev->pins->default_state))
>> +               nr_pins = 0;
>> +#endif
>
> Use:
>
> if (IS_ENABLED(CONFIG_PINCTRL))
>    nr_pins = 0;
>
> Without ifdefs. Grep kernel for examples.
> Read <linux/kconfig.h> for explanations.
>
> Put a comment above this to explain exactly why
> you do this.
>
>> +
>>         /* cmd + clock + bus-width pins */
>> -       for (idx = 0; idx < NUM_PINS(bus_width); idx++) {
>> +       for (idx = 0; idx < nr_pins; idx++) {
>>                 gpio = of_get_gpio(slot_np, idx);
>>                 if (!gpio_is_valid(gpio)) {
>>                         dev_err(host->dev, "invalid gpio: %d\n", gpio);
>
> This looks kludgy, is it so that the driver falls back to GPIO
> if it cannot use pinctrl? Can't it just depend on CONFIG_PINCTRL
> in Kconfig or do you absolutely have to support both cases?
>
> I was under the impression that the Exynos requires pinctrl.
>
> Yours,
> Linus Walleij
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