linux-kernel - Re: [PATCH] mmc: sdhci-pci-gli: Add runtime PM for GL9763E

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Date:   Wed, 2 Mar 2022 11:03:52 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Ben Chuang <benchuanggli@...il.com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        greg.tu@...esyslogic.com.tw,
        Ben Chuang <ben.chuang@...esyslogic.com.tw>,
        SeanHY.Chen@...esyslogic.com.tw,
        Kevin Chang <kevin.chang@...uturecenter.com>
Subject: Re: [PATCH] mmc: sdhci-pci-gli: Add runtime PM for GL9763E

On Wed, 2 Mar 2022 at 03:10, Ben Chuang <benchuanggli@...il.com> wrote:
>
> Hi,
>
> On Tue, Mar 1, 2022 at 6:05 PM Adrian Hunter <adrian.hunter@...el.com> wrote:
> >
> > On 28/02/2022 19:03, Ulf Hansson wrote:
> > > On Fri, 25 Feb 2022 at 13:56, Ben Chuang <benchuanggli@...il.com> wrote:
> > >>
> > >> From: Ben Chuang <ben.chuang@...esyslogic.com.tw>
> > >>
> > >> Add runtime PM for GL9763E and disable PLL in runtime suspend. So power
> > >> gated of upstream port can be enabled.
> > >>
> > >> Signed-off-by: Ben Chuang <ben.chuang@...esyslogic.com.tw>
> > >> Tested-by: Kevin Chang <kevin.chang@...uturecenter.com>
> > >> ---
> > >>  drivers/mmc/host/sdhci-pci-gli.c | 54 ++++++++++++++++++++++++++++++++
> > >>  1 file changed, 54 insertions(+)
> > >>
> > >> diff --git a/drivers/mmc/host/sdhci-pci-gli.c b/drivers/mmc/host/sdhci-pci-gli.c
> > >> index 97035d77c18c..cf99b6af792d 100644
> > >> --- a/drivers/mmc/host/sdhci-pci-gli.c
> > >> +++ b/drivers/mmc/host/sdhci-pci-gli.c
> > >> @@ -873,6 +873,55 @@ static void gli_set_gl9763e(struct sdhci_pci_slot *slot)
> > >>         pci_write_config_dword(pdev, PCIE_GLI_9763E_VHS, value);
> > >>  }
> > >>
> > >> +#ifdef CONFIG_PM
> > >> +static int gl9763e_runtime_suspend(struct sdhci_pci_chip *chip)
> > >> +{
> > >> +       struct sdhci_pci_slot *slot = chip->slots[0];
> > >> +       struct sdhci_host *host = slot->host;
> > >> +       u16 clock;
> > >> +
> > >> +       clock = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> > >> +       clock &= ~(SDHCI_CLOCK_PLL_EN | SDHCI_CLOCK_CARD_EN);
> > >> +       sdhci_writew(host, clock, SDHCI_CLOCK_CONTROL);
> > >> +
> > >> +       return 0;
> > >> +}
> > >> +
> > >> +static int gl9763e_runtime_resume(struct sdhci_pci_chip *chip)
> > >> +{
> > >> +       struct sdhci_pci_slot *slot = chip->slots[0];
> > >> +       struct sdhci_host *host = slot->host;
> > >> +       ktime_t timeout;
> > >> +       u16 clock;
> > >> +
> > >> +       clock = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> > >> +
> > >> +       clock |= SDHCI_CLOCK_PLL_EN;
> > >> +       clock &= ~SDHCI_CLOCK_INT_STABLE;
> > >> +       sdhci_writew(host, clock, SDHCI_CLOCK_CONTROL);
> > >> +
> > >> +       timeout = ktime_add_ms(ktime_get(), 150);
> > >> +       while (1) {
> > >> +               bool timedout = ktime_after(ktime_get(), timeout);
> > >> +
> > >> +               clock = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> > >> +               if (clock & SDHCI_CLOCK_INT_STABLE)
> > >> +                       break;
> > >> +               if (timedout) {
> > >> +                       pr_err("%s: PLL clock never stabilised.\n",
> > >> +                              mmc_hostname(host->mmc));
> > >> +                       sdhci_dumpregs(host);
> > >> +                       break;
> > >> +               }
> > >> +               udelay(10);
> > >> +       }
> >
> > Could use something like read_poll_timeout() here e.g.
> >
> >         if (read_poll_timeout(sdhci_readw, clk, (clk & SDHCI_CLOCK_INT_STABLE),
> >                               1000, 150000, false, host, SDHCI_CLOCK_CONTROL)) {
> >                 pr_err("%s: PLL clock never stabilised.\n",
> >                        mmc_hostname(host->mmc));
> >                 sdhci_dumpregs(host);
> >         }
> >
> >
>
> Thanks for the tip. I will prepare the next patch.
>
> > >> +       clock |= SDHCI_CLOCK_CARD_EN;
> > >> +       sdhci_writew(host, clock, SDHCI_CLOCK_CONTROL);
> > >> +
> > >> +       return 0;
> > >> +}
> > >
> > > Both functions above look very similar to what sdhci_set_clock() does.
> > > Can you use that, rather than open coding the above?
> > >
>
> The codes turn on/off the clock but it doesn't change the clock.
> Using sdhci_set_clock()  needs to store the clock value because it
> clears the clock.

Well, in that case at least you can call sdhci_enable_clk() from
gl9763e_runtime_resume(), rather than open coding it (the code looks
like a direct copy of that code). All you need is to give the
sdhci_enable_clk() the correct "clk" as in-parameter.

>
> > > Other than that, I would appreciate it if Adrian could have a look at
> > > this too. For example, I wonder if perhaps
> > > sdhci_runtime_suspend|resume_host() should be called in these paths
> > > too.
> >
> > Assuming the host controller does not lose state information, it should be fine.
> >
>
> Yes, the host always has aux. power and keep state.
>
> Thank you both for your comments.

Okay, thanks for confirming!

[...]

Kind regards
Uffe