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    SubjectRe: [PATCH 2/2] mmc: sdhci-of-at91: set clocks and presets after resume from deepest PM
    On 11 July 2017 at 15:33, Ludovic Desroches
    <ludovic.desroches@microchip.com> wrote:
    > On Tue, Jul 11, 2017 at 02:42:44PM +0200, Ulf Hansson wrote:
    >> On 16 June 2017 at 09:29, Quentin Schulz
    >> <quentin.schulz@free-electrons.com> wrote:
    >> > This adds deepest (Backup+Self-Refresh) PM support to the ATMEL SAMA5D2
    >> > SoC's SDHCI controller.
    >> >
    >> > When resuming from deepest state, it is required to restore preset
    >> > registers as the registers are lost since VDD core has been shut down
    >> > when entering deepest state on the SAMA5D2. The clocks need to be
    >> > reconfigured as well.
    >>
    >> Right, so compared to runtime resume there is some additional
    >> operations that is needed during system resume. Fair enough.
    >>
    >> However by looking at the changes below, you also change the system
    >> suspend operations, as it now calls sdhci_suspend_host(). Is that
    >> change needed? Then why?
    >>
    >> >
    >> > The other registers and init process are taken care of by the SDHCI
    >> > core.
    >> >
    >> > Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
    >> > ---
    >> > drivers/mmc/host/sdhci-of-at91.c | 34 ++++++++++++++++++++++++++++++++--
    >> > 1 file changed, 32 insertions(+), 2 deletions(-)
    >> >
    >> > diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
    >> > index fb8c6011f13d..300513fc1068 100644
    >> > --- a/drivers/mmc/host/sdhci-of-at91.c
    >> > +++ b/drivers/mmc/host/sdhci-of-at91.c
    >> > @@ -207,6 +207,37 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
    >> > }
    >> >
    >> > #ifdef CONFIG_PM
    >> > +static int sdhci_at91_suspend(struct device *dev)
    >> > +{
    >> > + struct sdhci_host *host = dev_get_drvdata(dev);
    >> > + struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
    >> > + struct sdhci_at91_priv *priv = sdhci_pltfm_priv(pltfm_host);
    >> > + int ret;
    >> > +
    >> > + ret = sdhci_suspend_host(host);
    >> > +
    >>
    >> This is wrong, you can't call sdhci_suspend_host() unless the device
    >> is runtime resumed...
    >>
    >> > + if (host->runtime_suspended)
    >> > + return ret;
    >>
    >> ... and this is weird...
    >>
    >> > +
    >> > + clk_disable_unprepare(priv->gck);
    >> > + clk_disable_unprepare(priv->hclock);
    >> > + clk_disable_unprepare(priv->mainck);
    >> > +
    >> > + return ret;
    >> > +}
    >> > +
    >> > +static int sdhci_at91_resume(struct device *dev)
    >> > +{
    >> > + struct sdhci_host *host = dev_get_drvdata(dev);
    >> > + int ret;
    >> > +
    >> > + ret = sdhci_at91_set_clks_presets(dev);
    >> > + if (ret)
    >> > + return ret;
    >>
    >> Instead of doing it like this, I suggest you set a new flag to true
    >> here, let's call it "restore_needed".
    >>
    >> In the ->runtime_resume() callback, you check the restore_needed flag
    >> and performs the extra operations in that case. When that's done, the
    >> ->runtime_resume() callback clears the flag, as to avoid the next
    >> runtime resume from unnecessary doing the extra operations.
    >>
    >> > +
    >> > + return sdhci_resume_host(host);
    >>
    >> Remove this and call pm_runtime_force_resume().
    >>
    >> > +}
    >> > +
    >> > static int sdhci_at91_runtime_suspend(struct device *dev)
    >> > {
    >> > struct sdhci_host *host = dev_get_drvdata(dev);
    >> > @@ -256,8 +287,7 @@ static int sdhci_at91_runtime_resume(struct device *dev)
    >> > #endif /* CONFIG_PM */
    >> >
    >> > static const struct dev_pm_ops sdhci_at91_dev_pm_ops = {
    >> > - SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
    >>
    >> Leave the pm_runtime_force_suspend() here, unless you have other
    >> reasons not being described in the change log, to change the system
    >> suspend operations.
    >
    > I think we need to keep it to be able to set the restore_needed flag, isn't it?

    Yeah, perhaps it's better to set the flag from sdhci_at91_suspend()
    and instead leave the resume callback being assigned to
    pm_runtime_force_resume().

    I guess that is what you meant?

    [...]

    Kind regards
    Uffe

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