linux-kernel - Re: [PATCH v9] mmc: sdhci-of-dwcmshc: Add runtime PM operations

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Message-ID: <CAPDyKFpEfc7EjpKDczwk9XDySug+uJ064FbrxsD6A0CY9ccOaw@mail.gmail.com>
Date:   Fri, 18 Aug 2023 12:19:18 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Liming Sun <limings@...dia.com>,
        David Thompson <davthompson@...dia.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9] mmc: sdhci-of-dwcmshc: Add runtime PM operations

On Fri, 18 Aug 2023 at 11:36, Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> On 18/08/23 12:00, Ulf Hansson wrote:
> > On Thu, 17 Aug 2023 at 18:22, Liming Sun <limings@...dia.com> 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>
> >> ---
> >> 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.

Kind regards
Uffe