linux-kernel - Re: [PATCH] regulator: s5m8767: Convert to GPIO descriptors

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Message-ID: <20250324033038.GA9886@nxa18884-linux>
Date: Mon, 24 Mar 2025 12:21:52 +0800
From: Peng Fan <peng.fan@....nxp.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Peng Fan <peng.fan@....com>,
	Andy Shevchenko <andriy.shevchenko@...el.com>,
	"lgirdwood@...il.com" <lgirdwood@...il.com>,
	"broonie@...nel.org" <broonie@...nel.org>,
	"linus.walleij@...aro.org" <linus.walleij@...aro.org>,
	"brgl@...ev.pl" <brgl@...ev.pl>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" <linux-samsung-soc@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH] regulator: s5m8767: Convert to GPIO descriptors

On Tue, Mar 18, 2025 at 02:48:05PM +0100, Krzysztof Kozlowski wrote:
>On 18/03/2025 13:38, Peng Fan wrote:
>>> Also the commit message doesn't tell anything about the existing DTS
>>> files.
>>> Do we have this device described in any in the kernel? Do we have any
>>> googled examples? Why I'm asking because often the issue is the
>>> incorrect setting of the polarity, which needs to be carefully checked,
>>> esp. for the voltage regulators case.
>> 
>> 
>> Under arch/arm/boot/dts/samsung/, a few dtsi files have the property 
>> with results from output of
>> `grep "s5m8767" ./arch/arm/boot/dts/samsung/ -rn | grep gpios`
>> 
>> Exynos5250-spring.dts uses GPIO_ACTIVE_LOW.
>> Others use GPIO_ACTIVE_HIGH.
>> 
>These are old devices and not many people are actually providing tests,
>so you need to preserve existing ABI. IOW, if previously GPIO flags were
>ignored, meaning "1" is ACTIVE_HIGH, then you must preserve this behavior.

Per google,
Manual Reset function is for Hardware reset in the Active mode.
If MR1B and MR2B is kept low during the VLDO3 is active state, the
system makes all internal presetting registers as default in the
active mode (automatic power on sequence). If this hardware reset
function is not required, connect MRB pin to high.

So the reset is ACTIVE LOW if my understanding is correct.

To keep DTS unchanged, we need update polarity in gpiolib to
force GPIO_ACTIVE_LOW.

please see whether this is ok for you.

Thanks,
Peng

>
>Best regards,
>Krzysztof