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

Ulf Hansson
2023-08-18T10:20:51Z

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