Re: [PATCH v9] mmc: sdhci-of-dwcmshc: Add runtime PM operations

Ulf Hansson
2023-08-18T09:02:22Z

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