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

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Message-ID: <CACqvRUYwwgRqid8AbLJ7bp+gTyHw2c=o-pj435Z0PDriJcnnKQ@mail.gmail.com>
Date: Wed, 2 Jul 2025 15:07:42 -0400
From: Da Xue <da@...re.computer>
To: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc: Da Xue <da@...re.computer>, Jerome Brunet <jbrunet@...libre.com>, 
	Anand Moon <linux.amoon@...il.com>, 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 2:40 PM Martin Blumenstingl
<martin.blumenstingl@...glemail.com> wrote:
>
> On Wed, Jul 2, 2025 at 7:22 PM Da Xue <da@...re.computer> wrote:
> >
> > 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.
> There's an exception to this: gpio-regulators without an enable-gpios
> property. My understanding is that regulator_disable() is a no-op in
> that case (meson_mmc_set_ios() even has a comment above the
> switch/case statement), see [0].
>
> > The code makes incorrect assumptions. Then the kernel resets the board
> > without having enough time.
> Can you please name the board you're testing? I'm worried that I'll be
> looking at one .dts but you're looking at another one.

https://github.com/libre-computer-project/libretech-linux/blob/master/arch/arm64/boot/dts/amlogic/meson-libretech-cottonwood.dtsi#L481

vcc_card is a gpio regulator that gets toggled on->off->on.

I traced the regulator framework a few weeks ago and forgot the final
regulator disable function call, but that call basically returned
immediately while the regulator-enable function complement had delays
implemented.

>
>
> Best regards,
> Martin
>
>
> [0] https://elixir.bootlin.com/linux/v6.15/source/drivers/regulator/core.c#L2980