Re: [PATCH 2/3] ASoC: codec: wcd938x: Convert to GPIO descriptors
From: Linus Walleij
Date: Mon Mar 24 2025 - 05:58:38 EST
On Mon, Mar 24, 2025 at 9:34 AM Peng Fan <peng.fan@xxxxxxx> wrote:
> > 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@xxxxxxx>
> > 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.
Actually when looking closer at it I was wrong.
>From <linux/gpio/consumer.h>:
enum gpiod_flags {
GPIOD_ASIS = 0,
GPIOD_IN = GPIOD_FLAGS_BIT_DIR_SET,
GPIOD_OUT_LOW = GPIOD_FLAGS_BIT_DIR_SET | GPIOD_FLAGS_BIT_DIR_OUT,
GPIOD_OUT_HIGH = GPIOD_FLAGS_BIT_DIR_SET | GPIOD_FLAGS_BIT_DIR_OUT |
GPIOD_FLAGS_BIT_DIR_VAL,
GPIOD_OUT_LOW_OPEN_DRAIN = GPIOD_OUT_LOW | GPIOD_FLAGS_BIT_OPEN_DRAIN,
GPIOD_OUT_HIGH_OPEN_DRAIN = GPIOD_OUT_HIGH | GPIOD_FLAGS_BIT_OPEN_DRAIN,
};
So GPIOD_ASIS does not set GPIOD_FLAGS_BIT_DIR_SET.
Then gpiod_configure_flags() has:
/* No particular flag request, return here... */
if (!(dflags & GPIOD_FLAGS_BIT_DIR_SET)) {
gpiod_dbg(desc, "no flags found for GPIO %s\n", name);
return 0;
}
/* 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);
So the function bails out right above (you could check the debug
print there if in doubt.)
So the behaviour is correct.
So now I have no idea what is going on again :/
But I would suggest trying to set GPIOD_OUT_LOW when requesting
the line and just check if that solves Steev:s problem
(trial-and-error).
Yours,
Linus Walleij