linux-kernel - RE: [PATCH 2/3] ASoC: codec: wcd938x: Convert to GPIO descriptors

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Message-ID:
 <PAXPR04MB8459F7BE5AD43E0685C74A6C88A42@PAXPR04MB8459.eurprd04.prod.outlook.com>
Date: Mon, 24 Mar 2025 08:34:57 +0000
From: Peng Fan <peng.fan@....com>
To: Linus Walleij <linus.walleij@...aro.org>
CC: Johan Hovold <johan@...nel.org>, Steev Klimaszewski <steev@...i.org>,
	"Peng Fan (OSS)" <peng.fan@....nxp.com>, Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, Jaroslav Kysela <perex@...ex.cz>, Takashi
 Iwai <tiwai@...e.com>, Bartosz Golaszewski <brgl@...ev.pl>, Srinivas
 Kandagatla <srinivas.kandagatla@...aro.org>, "linux-sound@...r.kernel.org"
	<linux-sound@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-gpio@...r.kernel.org"
	<linux-gpio@...r.kernel.org>, "linux-arm-msm@...r.kernel.org"
	<linux-arm-msm@...r.kernel.org>
Subject: RE: [PATCH 2/3] ASoC: codec: wcd938x: Convert to GPIO descriptors

> Subject: Re: [PATCH 2/3] ASoC: codec: wcd938x: Convert to GPIO
> descriptors
> 
> On Mon, Mar 24, 2025 at 9:09 AM Peng Fan <peng.fan@....com>
> wrote:
> 
> > ok, then the only suspecting point is
> > wcd938x->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_ASIS);
> >
> > I may need to use GPIOD_OUT_LOW to configure it to output as set
> raw
> > set value as 1.
> 
> I think there may be a bug in gpiod_configure_flags() in gpiolib.c:
> 
>         /* Process flags */
>         if (dflags & GPIOD_FLAGS_BIT_DIR_OUT)
>                 ret = gpiod_direction_output_nonotify(desc,
>                                 !!(dflags & GPIOD_FLAGS_BIT_DIR_VAL));
>         else
>                 ret = gpiod_direction_input_nonotify(desc);
> 
> Shouldn't this be:
> 
>         if (dflags & GPIOD_FLAGS_BIT_DIR_OUT)
>                 ret = gpiod_direction_output_nonotify(desc,
>                                 !!(dflags & GPIOD_FLAGS_BIT_DIR_VAL));
>         else if (dflags & GPIOD_FLAGS_BIT_DIR_SET)
>                 ret = gpiod_direction_input_nonotify(desc);

Using GPIO_ASIS should not change direction.
This change makes sense.

> 
> ?
> 
> As it looks, the line will be set into input mode unless explicitly
> requested as output...
> 
> However this means the patch also has another bug: you need to either:
> 
> 1. Specify GPIO_OUT_LOW when requesting it or 2. Explicitly call
> gpiod_direction_out() before setting the value.

1 is better before the gpiolib bug got fixed. Then no need change
direction twice.
2 is better aligned with current driver.

There is no rush, so I could use 2 if you'd fix the gpiolib.

BTW, could I still keep your R-b in my V2?

Thanks,
Peng.

> 
> Yours,
> Linus Walleij