linux-kernel - Re: [PATCH v1 08/10] ARM: dts: exynos: Add proper regulator states for suspend-to-mem for Exyno5250 smdk5250

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Message-ID: <CANAwSgSQrW8CCg7=rdN98EsoDZ0KsWv84DKOh3K4Jgmgz66XFQ@mail.gmail.com>
Date: Sat, 26 Apr 2025 11:42:07 +0530
From: Anand Moon <linux.amoon@...il.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Chanwoo Choi <cw00.choi@...sung.com>, Michael Turquette <mturquette@...libre.com>, 
	Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Alim Akhtar <alim.akhtar@...sung.com>, 
	"open list:MAXIM PMIC AND MUIC DRIVERS FOR EXYNOS BASED BO..." <linux-kernel@...r.kernel.org>, 
	"open list:COMMON CLK FRAMEWORK" <linux-clk@...r.kernel.org>, 
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@...r.kernel.org>, 
	"moderated list:ARM/SAMSUNG S3C, S5P AND EXYNOS ARM ARCHITECTURES" <linux-arm-kernel@...ts.infradead.org>, 
	"open list:ARM/SAMSUNG S3C, S5P AND EXYNOS ARM ARCHITECTURES" <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH v1 08/10] ARM: dts: exynos: Add proper regulator states
 for suspend-to-mem for Exyno5250 smdk5250

Hi Krzysztof,

On Fri, 25 Apr 2025 at 20:18, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On 25/04/2025 15:26, Anand Moon wrote:
> > The MAX77686 PMCI is able to power down and up key core supplies and other
> > voltage rails via PWRREQ signal to enter / exit (deep) sleep mode.
> > PWRREQ status is ignored during initial power up and down processes.
> > All programming must be done before the AP enterns the sleep mode by
> > pulling PWRREQ low since the AP does not have programming capability
> > in (deep) sleep mode.
> >
> > Add suspend-to-mem node to regulator core to be enabled or disabled
> > during system suspend and also support changing the regulator operating
> > mode during runtime and when the system enter sleep mode (stand by mode).
> >
> > Regulators which can be turned off during system suspend:
> >       -LDOn   :       2, 6-8, 10-12, 14-16,
> >         -BUCKn  :       1-4.
> > Use standard regulator bindings for it ('regulator-off-in-suspend').
>
> I do not believe you tested this but instead send whatever you found
> somewhere without actually understanding the code. In the past you were
> sending such patches - without knowing what they do and without actually
> testing.
>
> NAK
>
Thanks for your review comments,

All the MAX77686 control register supports On/Off Control by PWRREQ signal.

Once the Application Processor (AP) boots up, the AP is able to power
down and up key
core supplies and other voltage rails via PWRREQ signal to enter /
exit (deep) sleep mode.
PWRREQ status is ignored during initial power up and down processes.
All programming must be done before the AP enterns the sleep mode by
pulling PWRREQ l
ow since the AP does not have programming capability in (deep) sleep mode.

So PWRREQ has the following states for control registers

00: OFF (regardless of PWRREQ)
01: Output ON/OFF controlled by PWRREQ PWRREQ=H (1) : Output ON
PWRREQ=L (0) : Output OFF
10: unused
11: ON (Regardless of PWRREQ)

I have dome code mapping through the driver to understand this feature.
If there is some code improvement plz suggest so.

> Best regards,
> Krzysztof

Thanks
-Anand