linux-kernel - Re: [PATCH] mmc: dw_mmc: Don't send clock off command if power is off

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Date:	Sun, 22 Mar 2015 17:46:46 +0530
From:	Alim Akhtar <alim.akhtar@...il.com>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Jaehoon Chung <jh80.chung@...sung.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Sonny Rao <sonnyrao@...omium.org>,
	Andrew Bresticker <abrestic@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Addy Ke <addy.ke@...k-chips.com>,
	Alexandru Stan <amstan@...omium.org>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Chris Ball <chris@...ntf.net>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: dw_mmc: Don't send clock off command if power is off

Hi Doug,

On Fri, Mar 20, 2015 at 11:30 PM, Doug Anderson <dianders@...omium.org> wrote:
> We've already seen that it causes failures if we try to send the
> "SDMMC_CMD_UPD_CLK" command when power is off to the system.  Here's
> another case where we were doing it: we were sending an
> SDMMC_CMD_UPD_CLK to set the clock to 0 when the card was already
> powered off and the clock was already at 0.  Let's avoid that command
> and avoid problems.
>
> Signed-off-by: Doug Anderson <dianders@...omium.org>
> ---
>  drivers/mmc/host/dw_mmc.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 47dfd0e..aeec698 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -1172,8 +1172,9 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>
>                 break;
>         case MMC_POWER_OFF:
> -               /* Turn clock off before power goes down */
> -               dw_mci_setup_bus(slot, false);
> +               /* Turn clock off before power goes down; only if powered */
> +               if (slot->host->vqmmc_enabled)
> +                       dw_mci_setup_bus(slot, false);
>
vqmmc_enabled is always _true_ when entering MMC_POWER_OFF case..right?
Is this done for extra protection? Or do you have a case where vqmmc
is OFF and driver still calls dw_mci_setup_bus from here?

>                 if (!IS_ERR(mmc->supply.vmmc))
>                         mmc_regulator_set_ocr(mmc, mmc->supply.vmmc, 0);
> --
> 2.2.0.rc0.207.ga3a616c
>
> --
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-- 
Regards,
Alim
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