linux-kernel - Re: [PATCH] mmc: sdhci-omap: Add Support for Suspend/Resume

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Date:   Wed, 19 Feb 2020 16:32:34 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Faiz Abbas <faiz_abbas@...com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kishon <kishon@...com>, Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH] mmc: sdhci-omap: Add Support for Suspend/Resume

On Tue, 18 Feb 2020 at 15:08, Faiz Abbas <faiz_abbas@...com> wrote:
>
> Add power management ops which save and restore the driver context and
> facilitate a system suspend and resume.
>
> Signed-off-by: Faiz Abbas <faiz_abbas@...com>
> ---
>  drivers/mmc/host/sdhci-omap.c | 59 +++++++++++++++++++++++++++++++++++
>  1 file changed, 59 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-omap.c b/drivers/mmc/host/sdhci-omap.c
> index 882053151a47..a524c01da8de 100644
> --- a/drivers/mmc/host/sdhci-omap.c
> +++ b/drivers/mmc/host/sdhci-omap.c
> @@ -108,6 +108,11 @@ struct sdhci_omap_host {
>         struct pinctrl          *pinctrl;
>         struct pinctrl_state    **pinctrl_state;
>         bool                    is_tuning;
> +       /* Omap specific context save */
> +       u32                     con;
> +       u32                     hctl;
> +       u32                     sysctl;
> +       u32                     capa;
>  };
>
>  static void sdhci_omap_start_clock(struct sdhci_omap_host *omap_host);
> @@ -1233,11 +1238,65 @@ static int sdhci_omap_remove(struct platform_device *pdev)
>         return 0;
>  }
>
> +static void sdhci_omap_context_save(struct sdhci_omap_host *omap_host)
> +{
> +       omap_host->con = sdhci_omap_readl(omap_host, SDHCI_OMAP_CON);
> +       omap_host->hctl = sdhci_omap_readl(omap_host, SDHCI_OMAP_HCTL);
> +       omap_host->sysctl = sdhci_omap_readl(omap_host, SDHCI_OMAP_SYSCTL);
> +       omap_host->capa = sdhci_omap_readl(omap_host, SDHCI_OMAP_CAPA);
> +}
> +
> +static void sdhci_omap_context_restore(struct sdhci_omap_host *omap_host)
> +{
> +       sdhci_omap_writel(omap_host, SDHCI_OMAP_CON, omap_host->con);
> +       sdhci_omap_writel(omap_host, SDHCI_OMAP_HCTL, omap_host->hctl);
> +       sdhci_omap_writel(omap_host, SDHCI_OMAP_SYSCTL, omap_host->sysctl);
> +       sdhci_omap_writel(omap_host, SDHCI_OMAP_CAPA, omap_host->capa);
> +}
> +
> +static int __maybe_unused sdhci_omap_suspend(struct device *dev)
> +{
> +       struct sdhci_host *host = dev_get_drvdata(dev);
> +       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +       struct sdhci_omap_host *omap_host = sdhci_pltfm_priv(pltfm_host);
> +
> +       sdhci_suspend_host(host);
> +
> +       sdhci_omap_context_save(omap_host);
> +
> +       pinctrl_pm_select_idle_state(dev);
> +
> +       pm_runtime_put_sync(dev);

What exactly do you want to achieve by calling pm_runtime_put_sync() here?

Restoring the usage count from the pm_runtime_get_sync() during
->probe(), makes little sense to me. This because, the PM core is
preventing the device from being runtime suspended anyway, as it calls
pm_runtime_get_noresume() in device_prepare().

Or maybe there are other reasons?

> +
> +       return 0;
> +}
> +
> +static int __maybe_unused sdhci_omap_resume(struct device *dev)
> +{
> +       struct sdhci_host *host = dev_get_drvdata(dev);
> +       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +       struct sdhci_omap_host *omap_host = sdhci_pltfm_priv(pltfm_host);
> +
> +       pm_runtime_get_sync(dev);
> +
> +       pinctrl_pm_select_default_state(dev);
> +
> +       sdhci_omap_context_restore(omap_host);
> +
> +       sdhci_resume_host(host);
> +
> +       return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(sdhci_omap_dev_pm_ops, sdhci_omap_suspend,
> +                        sdhci_omap_resume);
> +
>  static struct platform_driver sdhci_omap_driver = {
>         .probe = sdhci_omap_probe,
>         .remove = sdhci_omap_remove,
>         .driver = {
>                    .name = "sdhci-omap",
> +                  .pm = &sdhci_omap_dev_pm_ops,
>                    .of_match_table = omap_sdhci_match,
>                   },
>  };
> --
> 2.19.2
>

Kind regards
Uffe