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

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Message-ID: <CANAwSgTH67T9SBQSFQgFjvyrxNCbtfd9ZaCDZFACWA=ZQ-PYtQ@mail.gmail.com>
Date: Tue, 1 Jul 2025 15:29:53 +0530
From: Anand Moon <linux.amoon@...il.com>
To: Da Xue <da@...re.computer>
Cc: Ulf Hansson <ulf.hansson@...aro.org>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Kevin Hilman <khilman@...libre.com>, Jerome Brunet <jbrunet@...libre.com>, 
	Martin Blumenstingl <martin.blumenstingl@...glemail.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

Hi Da,

On Sat, 28 Jun 2025 at 09:15, Da Xue <da@...re.computer> wrote:
>
> Regulators controlling the SD card power need some settling time for SD
> cards to fully reset from UHS modes. The regulator framework seems to
> ignore falling times set in the device tree causing a few boards with the
> same hardware implementation to hang on reboot because the SD card still
> had some voltage and did not reset properly to be initialized again.
>
> Add a delay sufficiently long for the voltage to drop so that the SD card
> can reset properly. Otherwise the reboot will hang at missing SD card
> especially with Samsung cards.
>
Although the driver defines reset identifiers such as
RESET_SD_EMMC_A, RESET_SD_EMMC_B, and RESET_SD_EMMC_C,
It does not implement proper reset controller functionality,
specifically lacking support
for reset_control_assert() and reset_control_deassert() operations.

Thanks
-Anand