linux-kernel - Re: [PATCH v4] mmc: sdhci-of-dwcmshc: Add runtime PM operations

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Message-ID: <9094e3c9-77fd-081f-244a-9454b81bd3b6@intel.com>
Date:   Fri, 19 May 2023 16:19:29 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Liming Sun <limings@...dia.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        David Thompson <davthompson@...dia.com>,
        Shawn Lin <shawn.lin@...k-chips.com>
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] mmc: sdhci-of-dwcmshc: Add runtime PM operations

On 12/05/23 21:15, Liming Sun wrote:
> This commit implements the runtime PM operations to disable eMMC
> card clock when idle.
> 
> Reviewed-by: David Thompson <davthompson@...dia.com>
> Signed-off-by: Liming Sun <limings@...dia.com>
> ---
> 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..2d780a5bc8fb 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>
>  
> @@ -546,6 +547,8 @@ static int dwcmshc_probe(struct platform_device *pdev)
>  		sdhci_enable_v4_mode(host);
>  #endif
>  
> +	pm_runtime_enable(dev);

Is there a reason to call it this early?  That raises questions
about runtime PM racing with the rest of the host initialization.
Perhaps below instead (note also using devm):

diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
index 2d780a5bc8fb..5cee42d72257 100644
--- a/drivers/mmc/host/sdhci-of-dwcmshc.c
+++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
@@ -547,8 +547,6 @@ static int dwcmshc_probe(struct platform_device *pdev)
 		sdhci_enable_v4_mode(host);
 #endif
 
-	pm_runtime_enable(dev);
-
 	host->mmc->caps |= MMC_CAP_WAIT_WHILE_BUSY;
 
 	err = sdhci_setup_host(host);
@@ -562,6 +560,8 @@ static int dwcmshc_probe(struct platform_device *pdev)
 	if (err)
 		goto err_setup_host;
 
+	devm_pm_runtime_enable(dev);
+
 	return 0;
 
 err_setup_host:


> +
>  	host->mmc->caps |= MMC_CAP_WAIT_WHILE_BUSY;
>  
>  	err = sdhci_setup_host(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);
> +	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);
> +	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 = sdhci_runtime_suspend_host(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;
> +
> +	dwcmshc_enable_card_clk(host);
> +	ret = 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)
> +	SET_RUNTIME_PM_OPS(dwcmshc_runtime_suspend,
> +			   dwcmshc_runtime_resume, NULL)
> +};
>  
>  static struct platform_driver sdhci_dwcmshc_driver = {
>  	.driver	= {