RE: [PATCH v9] mmc: sdhci-of-dwcmshc: Add runtime PM operations

[Liming Sun]

> -----Original Message-----
> From: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> Sent: Friday, August 18, 2023 6:19 AM
> To: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Cc: Liming Sun <limings@xxxxxxxxxx>; David Thompson
> <davthompson@xxxxxxxxxx>; Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>; linux-
> mmc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v9] mmc: sdhci-of-dwcmshc: Add runtime PM operations
> 
> On Fri, 18 Aug 2023 at 11:36, Adrian Hunter <adrian.hunter@xxxxxxxxx>
> wrote:
> >
> > On 18/08/23 12:00, Ulf Hansson wrote:
> > > On Thu, 17 Aug 2023 at 18:22, 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>
> > >> ---
> > >> v8->v9:
> > >>     - Address Adrian's comment to do the pm_runtime_put() in
> > >>       dwcmshc_resume() instead; Error path changes not included yet.
> > >> v7->v8:
> > >>     - Address Ulf's comment (option-1);
> > >>     - Updates for Adrian's comment to remove the force_suspend/resume
> > >>       in dwcmshc_resume()/dwcmshc_suspend(); Add comments for
> > >>       dwcmshc_resume()/dwcmshc_suspend();
> > >> v6->v7:
> > >>     - Address Ulf's comment;
> > >> 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 | 76
> +++++++++++++++++++++++++++--
> > >>  1 file changed, 72 insertions(+), 4 deletions(-)
> > >>
> > >> diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c
> b/drivers/mmc/host/sdhci-of-dwcmshc.c
> > >> index e68cd87998c8..3b40f55ce2a4 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(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);
> > >> @@ -602,9 +612,13 @@ static int dwcmshc_suspend(struct device *dev)
> > >>         struct rk35xx_priv *rk_priv = priv->priv;
> > >>         int ret;
> > >>
> > >> +       pm_runtime_get_sync(dev);
> > >> +
> > >>         ret = sdhci_suspend_host(host);
> > >> -       if (ret)
> > >> +       if (ret) {
> > >> +               pm_runtime_put(dev);
> > >>                 return ret;
> > >> +       }
> > >>
> > >>         clk_disable_unprepare(pltfm_host->clk);
> > >>         if (!IS_ERR(priv->bus_clk))
> > >> @@ -642,11 +656,65 @@ static int dwcmshc_resume(struct device *dev)
> > >>                         return ret;
> > >>         }
> > >>
> > >> -       return sdhci_resume_host(host);
> > >> +       ret = sdhci_resume_host(host);
> > >> +       if (ret)
> > >> +               return ret;
> > >> +
> > >> +       pm_runtime_put(dev);
> > >
> > > To simplify the error path, I would suggest that you move the call to
> > > pm_runtime_put() to dwcmshc_suspend(). In fact what you need is just a
> > > call to pm_runtime_put_noidle(), somewhere after the call to
> > > pm_runtime_get_sync().
> > >
> > > This is because runtime suspend is prevented by the PM core as it
> > > bumps the usage count with a pm_runtime_get_noresume() in the
> > > device_prepare() phase.
> >
> > I thought you didn't want to assume that, because in that case
> > it can just be pm_runtime_resume() instead of pm_runtime_get_sync(),
> > and then no 'put' is needed at all.
> 
> I don't really care, but just wanted to keep it as simple as possible.
> 
> So yes, I am fine with a pm_runtime_resume() too. Maybe even simpler
> in this case, as we are not using pm_runtime_force_suspend|resume()
> anymore.

Thanks. Will post v10 with ' pm_runtime_resume(dev);' in dwcmshc_suspend() to keep it simple.

> 
> Kind regards
> Uffe