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

[Ulf Hansson]

On Wed, 2 Mar 2022 at 12:56, Ben Chuang <benchuanggli@xxxxxxxxx> wrote:
>
> Hi,
>
> On Wed, Mar 2, 2022 at 6:04 PM Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote:
> >
> > On Wed, 2 Mar 2022 at 03:10, Ben Chuang <benchuanggli@xxxxxxxxx> wrote:
> > >
> > > Hi,
> > >
> > > On Tue, Mar 1, 2022 at 6:05 PM Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> > > >
> > > > On 28/02/2022 19:03, Ulf Hansson wrote:
> > > > > On Fri, 25 Feb 2022 at 13:56, Ben Chuang <benchuanggli@xxxxxxxxx> wrote:
> > > > >>
> > > > >> From: Ben Chuang <ben.chuang@xxxxxxxxxxxxxxxxxxx>
> > > > >>
> > > > >> 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@xxxxxxxxxxxxxxxxxxx>
> > > > >> Tested-by: Kevin Chang <kevin.chang@xxxxxxxxxxxxxxxxxx>
> > > > >> ---
> > > > >>  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.
> >
>
> I want to explain a little more,
> gl9763e is used as a boot disk controller.
> In gl9763e_runtime_suspend(), gl9763e still needs the internal clock to keep states.
> So gl9763e_runtime_suspend() only clears SDHCI_CLOCK_PLL_EN and SDHCI_CLOCK_CARD_EN.
> The SDHCI_CLOCK_INT_EN is still one (1) In runtime suspend,
>
> If using sdhci_enable_clk()  in gl9763e_runtime_resume(), sdhci_enable_clk()
> only fills one (1) to this bit (SDHCI_CLOCK_INT_EN) again, it cannot cause internal stable bit
> (SDHCI_CLOCK_INT_STABLE) to one for gl9763e in the first while loop.

Okay, I get it now, thanks for clarifying.

In any case, the loop in sdhci_enable_clk() that polls the
SDHCI_CLOCK_CONTROL register to see if the SDHCI_CLOCK_INT_STABLE is
set, could perhaps be split out to a function that you can use here as
well.

[...]

Kind regards
Uffe