linux-kernel - Re: [PATCH] mmc: sdhci-of-at91: fix wakeup issue when using runtime pm

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Message-ID: <CAPDyKFroVY0ZdqPScpGiJ8Y_QhhZ7asf0R0MzSx0WzVi5c2neg@mail.gmail.com>
Date:	Tue, 16 Feb 2016 15:38:29 +0100
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Ludovic Desroches <ludovic.desroches@...el.com>
Cc:	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH] mmc: sdhci-of-at91: fix wakeup issue when using runtime pm

On 13 February 2016 at 10:56, Ludovic Desroches
<ludovic.desroches@...el.com> wrote:
> When suspending the sdhci host, the only hardware event that could wake
> up the host is a sdio irq if they are enabled. If we want to wakeup on
> card detect events, a gpio as to be used.
> If we don't want to use a gpio but the card detect pio of the controller
> then we need to keep enabled the clock of the controller interface to
> get the interrupt and to not set the host in a suspended state to have the
> interrupt handled.
>
> Signed-off-by: Ludovic Desroches <ludovic.desroches@...el.com>
> ---
>  drivers/mmc/host/sdhci-of-at91.c | 46 ++++++++++++++++++++++++++++++----------
>  1 file changed, 35 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
> index efec736..2159c6e 100644
> --- a/drivers/mmc/host/sdhci-of-at91.c
> +++ b/drivers/mmc/host/sdhci-of-at91.c
> @@ -18,6 +18,7 @@
>  #include <linux/err.h>
>  #include <linux/io.h>
>  #include <linux/mmc/host.h>
> +#include <linux/mmc/slot-gpio.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/of_device.h>
> @@ -45,7 +46,6 @@ static const struct sdhci_ops sdhci_at91_sama5d2_ops = {
>
>  static const struct sdhci_pltfm_data soc_data_sama5d2 = {
>         .ops = &sdhci_at91_sama5d2_ops,
> -       .quirks = SDHCI_QUIRK_BROKEN_CARD_DETECTION,

You probably have some leftovers from earlier local changes, as this
isn't going to apply to my next branch.

>         .quirks2 = SDHCI_QUIRK2_NEED_DELAY_AFTER_INT_CLK_RST,
>  };
>
> @@ -55,17 +55,37 @@ static const struct of_device_id sdhci_at91_dt_match[] = {
>  };
>
>  #ifdef CONFIG_PM
> +static bool sdhci_at91_use_sdhci_runtime(struct sdhci_host *host)
> +{
> +       u32 caps = host->mmc->caps;
> +
> +       return (caps & MMC_CAP_NONREMOVABLE) ||
> +              (!IS_ERR_VALUE(mmc_gpio_get_cd(host->mmc)));
> +}
> +
>  static int sdhci_at91_runtime_suspend(struct device *dev)
>  {
>         struct sdhci_host *host = dev_get_drvdata(dev);
>         struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>         struct sdhci_at91_priv *priv = pltfm_host->priv;
> -       int ret;
> +       int ret = 0;
>
> -       ret = sdhci_runtime_suspend_host(host);
> +       /*
> +        * If we call sdhci_runtime_suspend(), we could wakeup only if sdio
> +        * irqs are enabled. If we want to wakeup on a card detect event there
> +        * are two options:
> +        * - do not call sdhci_runtime_suspend() but save power by disabling
> +        *   all clocks excepting the one for the controller interface.
> +        * - call sdhci_runtime_suspend(), save maximum power by disabling
> +        *   all clocks but use a gpio for the card detect signal to have a way
> +        *   to wakeup.
> +        */
> +       if (sdhci_at91_use_sdhci_runtime(host)) {

I am not sure this approach is safe, particularly for cases when
sdhci_runtime_suspend() isn't invoked.

As I understand it, in those cases potentially the sdhci's IRQ handler
may be invoked to serve even other IRQs than a card detect IRQ. Doing
that while being runtime suspended doesn't seem like a good idea. Will
it even work?

> +               ret = sdhci_runtime_suspend_host(host);
> +               clk_disable_unprepare(priv->hclock);
> +       }
>
>         clk_disable_unprepare(priv->gck);
> -       clk_disable_unprepare(priv->hclock);
>         clk_disable_unprepare(priv->mainck);
>
>         return ret;
> @@ -84,19 +104,23 @@ static int sdhci_at91_runtime_resume(struct device *dev)
>                 return ret;
>         }
>
> -       ret = clk_prepare_enable(priv->hclock);
> -       if (ret) {
> -               dev_err(dev, "can't enable hclock\n");
> -               return ret;
> -       }
> -
>         ret = clk_prepare_enable(priv->gck);
>         if (ret) {
>                 dev_err(dev, "can't enable gck\n");
>                 return ret;
>         }
>
> -       return sdhci_runtime_resume_host(host);
> +       if (sdhci_at91_use_sdhci_runtime(host)) {
> +               ret = clk_prepare_enable(priv->hclock);
> +               if (ret) {
> +                       dev_err(dev, "can't enable hclock\n");
> +                       return ret;
> +               }
> +
> +               ret = sdhci_runtime_resume_host(host);
> +       }
> +
> +       return ret;
>  }
>  #endif /* CONFIG_PM */
>
> --
> 2.7.0
>

Kind regards
Uffe