linux-kernel - Re: [PATCH 02/11] mmc: dw_mmc: Re-store SDIO IRQs mask at system resume

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Message-ID: <20190905170110.GJ70797@google.com>
Date:   Thu, 5 Sep 2019 10:01:10 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Douglas Anderson <dianders@...omium.org>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        Yong Mao <yong.mao@...iatek.com>,
        Chaotian Jing <chaotian.jing@...iatek.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 02/11] mmc: dw_mmc: Re-store SDIO IRQs mask at system
 resume

On Thu, Sep 05, 2019 at 09:29:04AM +0200, Ulf Hansson wrote:
> On Thu, 5 Sep 2019 at 02:14, Matthias Kaehlcke <mka@...omium.org> wrote:
> >
> > On Tue, Sep 03, 2019 at 04:21:58PM +0200, Ulf Hansson wrote:
> > > In cases when SDIO IRQs have been enabled, runtime suspend is prevented by
> > > the driver. However, this still means dw_mci_runtime_suspend|resume() gets
> > > called during system suspend/resume, via pm_runtime_force_suspend|resume().
> > > This means during system suspend/resume, the register context of the dw_mmc
> > > device most likely loses its register context, even in cases when SDIO IRQs
> > > have been enabled.
> > >
> > > To re-enable the SDIO IRQs during system resume, the dw_mmc driver
> > > currently relies on the mmc core to re-enable the SDIO IRQs when it resumes
> > > the SDIO card, but this isn't the recommended solution. Instead, it's
> > > better to deal with this locally in the dw_mmc driver, so let's do that.
> > >
> > > Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> > > ---
> > >  drivers/mmc/host/dw_mmc.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> > > index eea52e2c5a0c..f114710e82b4 100644
> > > --- a/drivers/mmc/host/dw_mmc.c
> > > +++ b/drivers/mmc/host/dw_mmc.c
> > > @@ -3460,6 +3460,10 @@ int dw_mci_runtime_resume(struct device *dev)
> > >       /* Force setup bus to guarantee available clock output */
> > >       dw_mci_setup_bus(host->slot, true);
> > >
> > > +     /* Re-enable SDIO interrupts. */
> > > +     if (sdio_irq_enabled(host->slot->mmc))
> > > +             __dw_mci_enable_sdio_irq(host->slot, 1);
> > > +
> > >       /* Now that slots are all setup, we can enable card detect */
> > >       dw_mci_enable_cd(host);
> >
> > Looks reasonable to me, besides the bikeshedding over
> > 'sdio_irq_enabled' (in "mmc: core: Add helper function to indicate
> > if SDIO IRQs is enabled").
> >
> > One thing I wonder is why this change is only needed for dw_mmc and
> > mtk-sd, but not for others like sunxi_mmc. Any insights for a SDIO
> > newb?
> 
> mtk-sd and dw_mmc is using MMC_CAP2_SDIO_IRQ_NOTHREAD and
> sdio_signal_irq(). This is also the case for sdhci, but sdhci is
> already internally dealing restoring SDIO IRQs during system resume.
> 
> The other host drivers haven't yet converted to
> MMC_CAP2_SDIO_IRQ_NOTHREAD. I have a series for that, not yet
> completed and thus not ready to be posted. Once that happens, all host
> drivers needs to care about re-enabling SDIO IRQs durings system
> resume as well.
> 
> For those host that currently doesn't use MMC_CAP2_SDIO_IRQ_NOTHREAD,
> the core wakes up the sdio_irq_thread from mmc_sdio_resume(), which
> later will calls the ->enable_sdio_irq().
> 
> Perhaps I should add some information about this in the changelog, let
> me think about it for the next version.

It makes sense now, thanks for the clarification!