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

[Ulf Hansson]

On Tue, 8 Aug 2023 at 15:21, Liming Sun <limings@xxxxxxxxxx> wrote:
>
>
>
> > -----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?

The ACPI PM domain doesn't support drivers using
pm_runtime_force_suspend|resume(). Unless that has been changed
without me knowing about it.

Anyway, it looks like it shouldn't be a problem at this point. We can
also add separate callbacks for other SoCs, if that comes into play
going forward.

[...]

Kind regards
Uffe