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    SubjectRe: [PATCH v9] mmc: sdhci-of-dwcmshc: Add runtime PM operations
    On Thu, 17 Aug 2023 at 18:22, Liming Sun <limings@nvidia.com> wrote:
    >
    > This commit implements the runtime PM operations to disable eMMC
    > card clock when idle.
    >
    > Reviewed-by: David Thompson <davthompson@nvidia.com>
    > Signed-off-by: Liming Sun <limings@nvidia.com>
    > ---
    > v8->v9:
    > - Address Adrian's comment to do the pm_runtime_put() in
    > dwcmshc_resume() instead; Error path changes not included yet.
    > v7->v8:
    > - Address Ulf's comment (option-1);
    > - Updates for Adrian's comment to remove the force_suspend/resume
    > in dwcmshc_resume()/dwcmshc_suspend(); Add comments for
    > dwcmshc_resume()/dwcmshc_suspend();
    > v6->v7:
    > - Address Ulf's comment;
    > v5->v6:
    > - Address Adrian's more comments and add coordination between
    > runtime PM and system PM;
    > v4->v5:
    > - Address Adrian's comment to move the pm_enable to the end to
    > avoid race;
    > v3->v4:
    > - Fix compiling reported by 'kernel test robot';
    > v2->v3:
    > - Revise the commit message;
    > v1->v2:
    > Updates for comments from Ulf:
    > - Make the runtime PM logic generic for sdhci-of-dwcmshc;
    > v1: Initial version.
    > ---
    > drivers/mmc/host/sdhci-of-dwcmshc.c | 76 +++++++++++++++++++++++++++--
    > 1 file changed, 72 insertions(+), 4 deletions(-)
    >
    > diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
    > index e68cd87998c8..3b40f55ce2a4 100644
    > --- a/drivers/mmc/host/sdhci-of-dwcmshc.c
    > +++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
    > @@ -15,6 +15,7 @@
    > #include <linux/module.h>
    > #include <linux/of.h>
    > #include <linux/of_device.h>
    > +#include <linux/pm_runtime.h>
    > #include <linux/reset.h>
    > #include <linux/sizes.h>
    >
    > @@ -548,9 +549,13 @@ static int dwcmshc_probe(struct platform_device *pdev)
    >
    > host->mmc->caps |= MMC_CAP_WAIT_WHILE_BUSY;
    >
    > + pm_runtime_get_noresume(dev);
    > + pm_runtime_set_active(dev);
    > + pm_runtime_enable(dev);
    > +
    > err = sdhci_setup_host(host);
    > if (err)
    > - goto err_clk;
    > + goto err_rpm;
    >
    > if (rk_priv)
    > dwcmshc_rk35xx_postinit(host, priv);
    > @@ -559,10 +564,15 @@ static int dwcmshc_probe(struct platform_device *pdev)
    > if (err)
    > goto err_setup_host;
    >
    > + pm_runtime_put(dev);
    > +
    > return 0;
    >
    > err_setup_host:
    > sdhci_cleanup_host(host);
    > +err_rpm:
    > + pm_runtime_disable(dev);
    > + pm_runtime_put_noidle(dev);
    > err_clk:
    > clk_disable_unprepare(pltfm_host->clk);
    > clk_disable_unprepare(priv->bus_clk);
    > @@ -602,9 +612,13 @@ static int dwcmshc_suspend(struct device *dev)
    > struct rk35xx_priv *rk_priv = priv->priv;
    > int ret;
    >
    > + pm_runtime_get_sync(dev);
    > +
    > ret = sdhci_suspend_host(host);
    > - if (ret)
    > + if (ret) {
    > + pm_runtime_put(dev);
    > return ret;
    > + }
    >
    > clk_disable_unprepare(pltfm_host->clk);
    > if (!IS_ERR(priv->bus_clk))
    > @@ -642,11 +656,65 @@ static int dwcmshc_resume(struct device *dev)
    > return ret;
    > }
    >
    > - return sdhci_resume_host(host);
    > + ret = sdhci_resume_host(host);
    > + if (ret)
    > + return ret;
    > +
    > + pm_runtime_put(dev);

    To simplify the error path, I would suggest that you move the call to
    pm_runtime_put() to dwcmshc_suspend(). In fact what you need is just a
    call to pm_runtime_put_noidle(), somewhere after the call to
    pm_runtime_get_sync().

    This is because runtime suspend is prevented by the PM core as it
    bumps the usage count with a pm_runtime_get_noresume() in the
    device_prepare() phase.

    > +
    > + return 0;
    > }
    > #endif

    [...]

    Kind regards
    Uffe

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