linux-kernel - Re: [RFC PATCH 2/2] mmc: core: sdio: claim host before power up or power off

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Date:	Fri, 11 Sep 2015 14:45:39 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Kishon Vijay Abraham I <kishon@...com>
Cc:	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sekhar Nori <nsekhar@...com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Neil Brown <neilb@...e.de>,
	"Fu, Zhonghui" <zhonghui.fu@...ux.intel.com>,
	Andreas Fenkart <afenkart@...il.com>
Subject: Re: [RFC PATCH 2/2] mmc: core: sdio: claim host before power up or
 power off

On 24 August 2015 at 12:15, Kishon Vijay Abraham I <kishon@...com> wrote:
> mmc_sdio_runtime_resume and mmc_sdio_runtime_suspend does power up and
> power off respectively but does so without claiming the host. Among other
> things mmc_claim_host inovkes pm_runtime_get_sync to enable the clocks.
> Invoke mmc_claim_host before mmc_power_up and mmc_power_off in
> mmc_sdio_runtime_resume and mmc_sdio_runtime_suspend respectively.
>
> This is required since certain platforms (like TI SoCs) access
> the controller registers during power up.

I realize the issue. Actually I have been working on similar patch
which take a bit wider approach. That's because there are more cases
where the host needs to be claimed, when it isn't.

I just posted a patch, please have a look and see if it makes sense to
you, you are on cc.
"[PATCH] mmc: core: Keep host claimed while invoking mmc_power_off|up()"

Kind regards
Uffe

>
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  drivers/mmc/core/sdio.c |   10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> index 0cbbfb8..40795b2 100644
> --- a/drivers/mmc/core/sdio.c
> +++ b/drivers/mmc/core/sdio.c
> @@ -1023,16 +1023,24 @@ static int mmc_sdio_power_restore(struct mmc_host *host)
>
>  static int mmc_sdio_runtime_suspend(struct mmc_host *host)
>  {
> +       mmc_claim_host(host);
>         /* No references to the card, cut the power to it. */
>         mmc_power_off(host);
> +       mmc_release_host(host);
>         return 0;
>  }
>
>  static int mmc_sdio_runtime_resume(struct mmc_host *host)
>  {
> +       int ret;
> +
> +       mmc_claim_host(host);
>         /* Restore power and re-initialize. */
>         mmc_power_up(host, host->card->ocr);
> -       return mmc_sdio_power_restore(host);
> +       ret = _mmc_sdio_power_restore(host);
> +       mmc_release_host(host);
> +
> +       return ret;
>  }
>
>  static int mmc_sdio_reset(struct mmc_host *host)
> --
> 1.7.9.5
>
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