Re: [PATCH v5] mmc: sdhci-of-dwcmshc: Add runtime PM operations

[Adrian Hunter <adrian.hunter@intel.com>]

On 28/07/23 15:20, Liming Sun 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>
> ---
> 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 | 54 ++++++++++++++++++++++++++++-
>  1 file changed, 53 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
> index e68cd87998c8..5cee42d72257 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>
>  
> @@ -559,6 +560,8 @@ static int dwcmshc_probe(struct platform_device *pdev)
>  	if (err)
>  		goto err_setup_host;
>  
> +	devm_pm_runtime_enable(dev);

By default, runtime PM regards the device as not active, so
typically drivers will use something like pm_runtime_set_active()
prior to pm_runtime_enable(dev)

In fact it is better to enable before adding the host but
increment the usage count to prevent runtime suspend.  That
means adding some get/puts, ending up with something like:

+	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);

	err = __sdhci_add_host(host);
	if (err)
		goto err_setup_host;

+	pm_runtime_put_sync(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);
	if (rk_priv)
		clk_bulk_disable_unprepare(RK35xx_MAX_CLKS,
					   rk_priv->rockchip_clks);
free_pltfm:
	sdhci_pltfm_free(pdev);
	return err;

> +
>  	return 0;
>  
>  err_setup_host:
> @@ -646,7 +649,56 @@ static int dwcmshc_resume(struct device *dev)
>  }
>  #endif
>  
> -static SIMPLE_DEV_PM_OPS(dwcmshc_pmops, dwcmshc_suspend, dwcmshc_resume);
> +#ifdef CONFIG_PM
> +
> +static void dwcmshc_enable_card_clk(struct sdhci_host *host)
> +{
> +	u16 ctrl;
> +
> +	ctrl = sdhci_readw(host, SDHCI_CLOCK_CONTROL);

You could save an mmio write:

	if (ctrl & SDHCI_CLOCK_INT_EN && !(ctrl & SDHCI_CLOCK_CARD_EN)) {

> +	ctrl |= SDHCI_CLOCK_CARD_EN;
> +	sdhci_writew(host, ctrl, SDHCI_CLOCK_CONTROL);

	}

> +}
> +
> +static void dwcmshc_disable_card_clk(struct sdhci_host *host)
> +{
> +	u16 ctrl;
> +
> +	ctrl = sdhci_readw(host, SDHCI_CLOCK_CONTROL);

You could save an mmio write:

	if (ctrl & SDHCI_CLOCK_CARD_EN) {

> +	ctrl &= ~SDHCI_CLOCK_CARD_EN;
> +	sdhci_writew(host, ctrl, SDHCI_CLOCK_CONTROL);

	}

> +}
> +
> +static int dwcmshc_runtime_suspend(struct device *dev)
> +{
> +	struct sdhci_host *host = dev_get_drvdata(dev);
> +	int ret = 0;

ret doesn't need initialization

> +
> +	ret = sdhci_runtime_suspend_host(host);

If you *only* want to disable the card clock, then
it is probably not necessary to call sdhci_runtime_suspend_host()
and sdhci_runtime_resume_host().

> +	if (!ret)
> +		dwcmshc_disable_card_clk(host);
> +
> +	return ret;
> +}
> +
> +static int dwcmshc_runtime_resume(struct device *dev)
> +{
> +	struct sdhci_host *host = dev_get_drvdata(dev);
> +	int ret = 0;

ret isn't needed

> +
> +	dwcmshc_enable_card_clk(host);
> +	ret = sdhci_runtime_resume_host(host, 0);

just
	return sdhci_runtime_resume_host(host, 0);

> +
> +	return ret;
> +}
> +
> +#endif
> +
> +static const struct dev_pm_ops dwcmshc_pmops = {
> +	SET_SYSTEM_SLEEP_PM_OPS(dwcmshc_suspend, dwcmshc_resume)

Typically you need a way to coordinate runtime PM and system PM, refer:

https://www.kernel.org/doc/html/latest/power/runtime_pm.html#runtime-pm-and-system-sleep

> +	SET_RUNTIME_PM_OPS(dwcmshc_runtime_suspend,
> +			   dwcmshc_runtime_resume, NULL)
> +};
>  
>  static struct platform_driver sdhci_dwcmshc_driver = {
>  	.driver	= {