linux-kernel - Re: [PATCH 4/7] ASoC: codec: cs42l56: Convert to GPIO descriptors

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Message-ID: <Z/UcOz7RlWSquLXH@opensource.cirrus.com>
Date: Tue, 8 Apr 2025 13:53:15 +0100
From: Charles Keepax <ckeepax@...nsource.cirrus.com>
To: "Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc: Shenghao Ding <shenghao-ding@...com>, Kevin Lu <kevin-lu@...com>,
        Baojun Xu <baojun.xu@...com>, Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Peter Ujfalusi <peter.ujfalusi@...il.com>,
        David Rhodes <david.rhodes@...rus.com>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>,
        linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-gpio@...r.kernel.org, patches@...nsource.cirrus.com,
        Peng Fan <peng.fan@....com>
Subject: Re: [PATCH 4/7] ASoC: codec: cs42l56: Convert to GPIO descriptors

On Tue, Apr 08, 2025 at 09:40:00AM +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@....com>
> Checking the current driver using legacy GPIO API, the
> nreset value is first output HIGH, then LOW, then HIGH.
> 
> Checking the datasheet, nreset is should be held low after power
> on, when nreset is high, it starts to work.
> 

Does feel like it would have made more sense to request it in
reset at the start certainly, but as you say reasonable to leave
well enough alone.

> Per datasheet, the DTS polarity should be GPIOD_ACTIVE_LOW. The binding
> example use value 0(GPIOD_ACTIVE_HIGH) which seems wrong. There is
> no in-tree DTS has the device, so all should be fine.

Yeah it is technically wrong, discussed more below.

> -	pdata->gpio_nreset = of_get_named_gpio(np, "cirrus,gpio-nreset", 0);
> +	pdata->gpio_nreset = devm_gpiod_get_optional(&i2c_client->dev, "cirrus,gpio-nreset",
> +						     GPIOD_OUT_LOW);

Would be nice to call out that this part is already included in
the quirks array in of_find_gpio_rename:

944004eb56dc ("gpiolib: of: add a quirk for reset line for Cirrus CS42L56")

Took me a while to realise this would request the right property.

> -		gpio_set_value_cansleep(cs42l56->pdata.gpio_nreset, 0);
> -		gpio_set_value_cansleep(cs42l56->pdata.gpio_nreset, 1);
> +		gpiod_set_value_cansleep(cs42l56->pdata.gpio_nreset, 1);
> +		gpiod_set_value_cansleep(cs42l56->pdata.gpio_nreset, 0);

I can't say I super love this change as it will mean any users
with a DT that worked with the driver before this change will see
things break. As far as I know the parts you are updating in
this series do not have a lot of users, (and none in tree as you
note) so I guess if everyone else is happy, I don't really object.

Thanks,
Charles