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

[Liming Sun]

> -----Original Message-----
> From: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> Sent: Tuesday, August 8, 2023 5:40 AM
> To: Liming Sun <limings@xxxxxxxxxx>
> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>; David Thompson
> <davthompson@xxxxxxxxxx>; Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>; linux-
> mmc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v6] mmc: sdhci-of-dwcmshc: Add runtime PM operations
> 
> On Sat, 5 Aug 2023 at 01:30, Liming Sun <limings@xxxxxxxxxx> wrote:
> >
> > This commit implements the runtime PM operations to disable eMMC
> > card clock when idle.
> >
> > Reviewed-by: David Thompson <davthompson@xxxxxxxxxx>
> > Signed-off-by: Liming Sun <limings@xxxxxxxxxx>
> > ---
> > 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