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Message-ID:
<DU0PR04MB9496801A4571142F914BBF4990402@DU0PR04MB9496.eurprd04.prod.outlook.com>
Date: Fri, 18 Oct 2024 03:20:29 +0000
From: Bough Chen <haibo.chen@....com>
To: Ulf Hansson <ulf.hansson@...aro.org>
CC: "adrian.hunter@...el.com" <adrian.hunter@...el.com>,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
"imx@...ts.linux.dev" <imx@...ts.linux.dev>, "shawnguo@...nel.org"
<shawnguo@...nel.org>, "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
"kernel@...gutronix.de" <kernel@...gutronix.de>, "festevam@...il.com"
<festevam@...il.com>, dl-S32 <S32@....com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/4] mmc: host: sdhci-esdhc-imx: refactor the system PM
logic
> -----Original Message-----
> From: Bough Chen
> Sent: 2024年10月18日 9:23
> To: Ulf Hansson <ulf.hansson@...aro.org>
> Cc: adrian.hunter@...el.com; linux-mmc@...r.kernel.org; imx@...ts.linux.dev;
> shawnguo@...nel.org; s.hauer@...gutronix.de; kernel@...gutronix.de;
> festevam@...il.com; dl-S32 <S32@....com>;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: RE: [PATCH 2/4] mmc: host: sdhci-esdhc-imx: refactor the system PM
> logic
>
> > -----Original Message-----
> > From: Ulf Hansson <ulf.hansson@...aro.org>
> > Sent: 2024年10月17日 21:07
> > To: Bough Chen <haibo.chen@....com>
> > Cc: adrian.hunter@...el.com; linux-mmc@...r.kernel.org;
> > imx@...ts.linux.dev; shawnguo@...nel.org; s.hauer@...gutronix.de;
> > kernel@...gutronix.de; festevam@...il.com; dl-S32 <S32@....com>;
> > linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> > Subject: Re: [PATCH 2/4] mmc: host: sdhci-esdhc-imx: refactor the
> > system PM logic
> >
> > On Mon, 14 Oct 2024 at 08:00, <haibo.chen@....com> wrote:
> > >
> > > From: Haibo Chen <haibo.chen@....com>
> > >
> > > Current suspend/resume logic has one issue. in suspend, will config
> > > register when call sdhci_suspend_host(), but at this time, can't
> > > guarantee host in runtime resume state. if not, the per clock is
> > > gate off, access register will hung.
> > >
> > > Now use pm_runtime_force_suspend/resume() in
> NOIRQ_SYSTEM_SLEEP_PM,
> > > add in NOIRQ stage can cover SDIO wakeup feature, because in
> > > interrupt handler, there is register access, need the per clock on.
> > >
> > > In sdhci_esdhc_suspend/sdhci_esdhc_resume, remove
> > > sdhci_suspend_host() and sdhci_resume_host(), all are handled in
> > > runtime PM callbacks except the wakeup irq setting.
> > >
> > > Remove pinctrl_pm_select_default_state() in sdhci_esdhc_resume,
> > > because
> > > pm_runtime_force_resume() already config the pinctrl state according
> > > to ios timing, and here config the default pinctrl state again is
> > > wrong for
> > > SDIO3.0 device if it keep power in suspend.
> >
> > I had a look at the code - and yes, there are certainly several
> > problems with PM support in this driver.
> >
> > >
> > > Signed-off-by: Haibo Chen <haibo.chen@....com>
> > > ---
> > > drivers/mmc/host/sdhci-esdhc-imx.c | 39
> > > +++++++++++++++---------------
> > > 1 file changed, 19 insertions(+), 20 deletions(-)
> > >
> > > diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c
> > > b/drivers/mmc/host/sdhci-esdhc-imx.c
> > > index c7582ad45123..18febfeb60cf 100644
> > > --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> > > +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> > > @@ -1871,11 +1871,13 @@ static int sdhci_esdhc_suspend(struct device
> > *dev)
> > > struct pltfm_imx_data *imx_data = sdhci_pltfm_priv(pltfm_host);
> > > int ret;
> > >
> > > - if (host->mmc->caps2 & MMC_CAP2_CQE) {
> > > - ret = cqhci_suspend(host->mmc);
> > > - if (ret)
> > > - return ret;
> > > - }
> > > + /*
> > > + * Switch to runtime resume for two reasons:
> > > + * 1, there is register access, so need to make sure gate on ipg
> clock.
> >
> > You are right that we need to call pm_runtime_get_sync() for this reason.
> >
> > However, the real question is rather; Under what circumstances do we
> > really need to make a register access beyond this point?
> >
> > If the device is already runtime suspended, I am sure we could just
> > leave it in that state without having to touch any of its registers.
> >
> > As I understand it, there are mainly two reasons why the device may be
> > runtime resumed at this point:
> > *) The runtime PM usage count has been bumped in
> > sdhci_enable_sdio_irq(), since the SDIO irqs are enabled and it's
> > likely that we will configure them for system wakeup too.
> > *) The device has been used, but nothing really prevents it from being
> > put into a low power state via the ->runtime_suspend() callback.
> >
> > > + * 2, make sure the pm_runtime_force_suspend() in NOIRQ
> > > + stage
> > really
> > > + * invoke its ->runtime_suspend callback.
> > > + */
> >
> > Rather than using the *noirq-callbacks, we should be able to call
> > pm_runtime_force_suspend() from sdhci_esdhc_suspend(). And vice versa
> > for sdhci_esdhc_resume().
> >
> > Although, according to my earlier comment above, we also need to take
> > into account the SDIO irq. If it's being enabled for system wakeup, we
> > must not put the controller into low power mode by calling
> > pm_runtime_force_suspend(), otherwise we will not be able to deliver the
> wakeup, right?
>
> Thanks for your careful review!
> Yes, I agree.
Hi Ulf,
Sorry, I maybe give the wrong answer.
I double check the IP, usdhc can support sdio irq wakeup even when usdhc clock gate off.
So to save power, need to call pm_runtime_force_suspend() to gate off the clock when enable sdio irq for system wakeup.
This is the main reason I involve pm_runtime_force_suspend in noirq stage, because in sdhci_irq, there is register access, need gate on clock.
Best Regards
Haibo Chen
>
> >
> > > + pm_runtime_get_sync(dev);
> > >
> > > if ((imx_data->socdata->flags &
> > ESDHC_FLAG_STATE_LOST_IN_LPMODE) &&
> > > (host->tuning_mode != SDHCI_TUNING_MODE_1))
> { @@
> > > -1883,12 +1885,11 @@ static int sdhci_esdhc_suspend(struct device *dev)
> > > mmc_retune_needed(host->mmc);
> > > }
> > >
> > > - if (host->tuning_mode != SDHCI_TUNING_MODE_3)
> > > - mmc_retune_needed(host->mmc);
> > > -
> > > - ret = sdhci_suspend_host(host);
> > > - if (ret)
> > > - return ret;
> > > + if (device_may_wakeup(dev)) {
> > > + ret = sdhci_enable_irq_wakeups(host);
> > > + if (!ret)
> > > + dev_warn(dev, "Failed to enable irq
> wakeup\n");
> > > + }
> > >
> > > ret = pinctrl_pm_select_sleep_state(dev);
> > > if (ret)
> > > @@ -1904,22 +1905,18 @@ static int sdhci_esdhc_resume(struct device
> > *dev)
> > > struct sdhci_host *host = dev_get_drvdata(dev);
> > > int ret;
> > >
> > > - ret = pinctrl_pm_select_default_state(dev);
> > > + ret = mmc_gpio_set_cd_wake(host->mmc, false);
> > > if (ret)
> > > return ret;
> > >
> > > /* re-initialize hw state in case it's lost in low power mode */
> > > sdhci_esdhc_imx_hwinit(host);
> >
> > This looks like another special use-case. If I understand correctly,
> > on some platforms some additional re-initialization of the controller
> > may be needed at system resume.
> >
> > If you want to move towards using pm_runtime_force_suspend|resume(), I
> > suggest moving the above call into the ->runtime_resume() callback. To
> > allow the ->runtime_resume() callback to know when this
> > re-initialization is needed, we can use a flag that we set here and
> > clear in the ->runtime_resume() callback.
>
> Yes, I can do like that. Seems I can remove the NOIRQ in v2.
>
> Thanks for your suggestion
>
> Regards
> Haibo Chen
>
>
> >
> > >
> > > - ret = sdhci_resume_host(host);
> > > - if (ret)
> > > - return ret;
> > > -
> > > - if (host->mmc->caps2 & MMC_CAP2_CQE)
> > > - ret = cqhci_resume(host->mmc);
> > > + if (host->irq_wake_enabled)
> > > + sdhci_disable_irq_wakeups(host);
> > >
> > > - if (!ret)
> > > - ret = mmc_gpio_set_cd_wake(host->mmc, false);
> > > + pm_runtime_mark_last_busy(dev);
> > > + pm_runtime_put_autosuspend(dev);
> > >
> > > return ret;
> > > }
> > > @@ -2011,6 +2008,8 @@ static const struct dev_pm_ops
> > > sdhci_esdhc_pmops
> > = {
> > > SET_SYSTEM_SLEEP_PM_OPS(sdhci_esdhc_suspend,
> > sdhci_esdhc_resume)
> > > SET_RUNTIME_PM_OPS(sdhci_esdhc_runtime_suspend,
> > > sdhci_esdhc_runtime_resume,
> NULL)
> > > +
> SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
> > > +
> pm_runtime_force_resume)
> > > };
> > >
> > > static struct platform_driver sdhci_esdhc_imx_driver = {
> > > --
> > > 2.34.1
> > >
> >
> > Kind regards
> > Uffe
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