Re: [PATCH 05/11] mmc: core: Enable eMMC sleep commands to use HW busy polling

From: Linus Walleij
Date: Thu May 06 2021 - 08:55:22 EST

On Tue, May 4, 2021 at 6:12 PM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:

> After the eMMC sleep command (CMD5) has been sent, the card start signals
> busy on the DAT0 line, which can be monitored to understand when it's
> allowed to proceed to power off the VCC regulator.
> When MMC_CAP_WAIT_WHILE_BUSY isn't supported by the host the DAT0 line
> isn't being monitored for busy completion, but instead we are waiting a
> fixed period of time. The time corresponds to the sleep timeout that is
> specified in the EXT_CSD register of the eMMC card. This is many cases
> suboptimal, as the timeout corresponds to the worst case scenario.
> To improve the situation add support for HW busy polling through the
> ->card_busy() host ops, when the host supports this.
> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>

Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Linus Walleij