linux-kernel - Re: [RFC] mmc: meson-gx-mmc: add delay during poweroff

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Message-ID: <CACqvRUa8EqMbCd2x=di-a6jbMWW8CMo4kgLH=0qnsqHdO16kxA@mail.gmail.com>
Date: Wed, 2 Jul 2025 13:22:15 -0400
From: Da Xue <da@...re.computer>
To: Jerome Brunet <jbrunet@...libre.com>
Cc: Martin Blumenstingl <martin.blumenstingl@...glemail.com>, Anand Moon <linux.amoon@...il.com>, 
	Da Xue <da@...re.computer>, Ulf Hansson <ulf.hansson@...aro.org>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Kevin Hilman <khilman@...libre.com>, 
	linux-mmc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC] mmc: meson-gx-mmc: add delay during poweroff

On Wed, Jul 2, 2025 at 1:07 PM Jerome Brunet <jbrunet@...libre.com> wrote:
...
> If, as the description suggest, the regulator framework somehow ignore
> the timing set in DT, maybe this is what needs to be checked ?

The regulator framework only cares about timing for regulator on.
Regulator off just turns off the regulator and returns without delay.
The code makes incorrect assumptions. Then the kernel resets the board
without having enough time.
I can patch the regulator framework with the same code for regulator
on but that seems very hazardous given how many things might already
depend on the original behavior of returning immediately.

>
> TBH I would suspect the delays before the regulator framework itself.
>
> Those assert/de-assert delays tend to be just copied from boards to
> boards. Maybe some boards need different delays. If those are too short
> for the actual HW, an ON -> OFF -> ON could result in a NOP.

50ms should be sufficient for all boards as many boards don't even
have this functionality. < 30ms is sufficient most of the time.

>
...
>
> --
> Jerome