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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250408155850.GA31497@nxa18884-linux>
Date: Tue, 8 Apr 2025 23:58:50 +0800
From: Peng Fan <peng.fan@....nxp.com>
To: Charles Keepax <ckeepax@...nsource.cirrus.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 01:53:15PM +0100, Charles Keepax wrote:
>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.

yeah. request it in reset state and set HIGH later is better.

I could update to use this new flow.

>
>> 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")

I will update commit log to include this.

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

My bad.

>
>> -		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.

A polarity quirk could be added to gpiolib-of, if this is preferred.
Before adding quirk, I would like to see whether Linus and Bartosz agree
on this.

BTW, [1] shows the chip is discontinued. Since there is no in-tree user
for quite some time, and new users would not use end-of-life chips,
should we totally delete this driver?

[1] https://www.cirrus.com/products/cs42l56/
  

Thanks,
Peng

>
>Thanks,
>Charles
>