RE: [PATCH v6] mmc: sdhci-of-dwcmshc: Add runtime PM operations

Liming Sun
2023-08-08T16:03:54Z

> -----Original Message-----
> From: Ulf Hansson <ulf.hansson@linaro.org>
> Sent: Tuesday, August 8, 2023 5:40 AM
> To: Liming Sun <limings@nvidia.com>
> Cc: Adrian Hunter <adrian.hunter@intel.com>; David Thompson
> <davthompson@nvidia.com>; Shawn Lin <shawn.lin@rock-chips.com>; linux-
> mmc@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v6] mmc: sdhci-of-dwcmshc: Add runtime PM operations
>
> On Sat, 5 Aug 2023 at 01:30, 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>
> > ---
> > 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 | 72
> ++++++++++++++++++++++++++++-
> > 1 file changed, 70 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-
> of-dwcmshc.c
> > index e68cd87998c8..aaf66358f626 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_sync(dev);
> > +
>
> The async pm_runtime_put() is probably sufficient - and it would allow
> the probe to complete a bit "sooner".

Sure, will test and update the line in v7.

>
> > 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);
> > @@ -606,6 +616,12 @@ static int dwcmshc_suspend(struct device *dev)
> > if (ret)
> > return ret;
> >
> > + ret = pm_runtime_force_suspend(dev);
>
> Can dwcmshc_suspend() be called for a device that may be attached to
> the ACPI PM domain?

BlueField SoC is the only chip that uses ACPI in this driver for now and it doesn't support System Sleep. Thus, the dwcmshc_suspend() won't be called. But I guess it might be possible when other new chip support is added into this driver. Is it a concern?

>
> > + if (ret) {
> > + sdhci_resume_host(host);
> > + return ret;
> > + }
> > +
> > clk_disable_unprepare(pltfm_host->clk);
> > if (!IS_ERR(priv->bus_clk))
> > clk_disable_unprepare(priv->bus_clk);
> > @@ -625,6 +641,10 @@ static int dwcmshc_resume(struct device *dev)
> > struct rk35xx_priv *rk_priv = priv->priv;
> > int ret;
> >
> > + ret = pm_runtime_force_resume(dev);
> > + if (ret)
> > + return ret;
> > +
> > ret = clk_prepare_enable(pltfm_host->clk);
> > if (ret)
> > return ret;
> > @@ -646,7 +666,55 @@ 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);
> > + 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);
> > + 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);
> > +
> > + dwcmshc_disable_card_clk(host);
> > +
> > + return 0;
> > +}
> > +
> > +static int dwcmshc_runtime_resume(struct device *dev)
> > +{
> > + struct sdhci_host *host = dev_get_drvdata(dev);
> > +
> > + dwcmshc_enable_card_clk(host);
> > +
> > + return 0;
> > +}
> > +
> > +#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 = {
> > --
>
> Kind regards
> Uffe