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

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Message-ID: <CACRpkdY2fScL3jvKoyR1m3+Yxj2=Nj3PPGm1cAqyn3kBS78aow@mail.gmail.com>
Date:   Thu, 6 May 2021 14:55:01 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     linux-mmc <linux-mmc@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Avri Altman <avri.altman@....com>,
        Masami Hiramatsu <masami.hiramatsu@...aro.org>,
        linux-block <linux-block@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 05/11] mmc: core: Enable eMMC sleep commands to use HW
 busy polling

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

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

Yours,
Linus Walleij