[PATCH 2/2] mmc: sdhci-brcmstb: Add ability to increase max clock rate for 72116b0

[Alan Cooper]

This seems confusing and seems to overload the meaning of
"max-frequency" which is typically used to limit the clock rate to
something slower than what's in the CAPs register as the base clock.
Instead we're trying to overclock the controller because the hardware
team has verified that it can be run faster than 100MHz which is how
the system is configured and is in the CAPs register as the base
clock.

Al

On Tue, May 17, 2022 at 8:50 AM Ulf Hansson <ulf.hansson at linaro.org> wrote:
>
> On Fri, 13 May 2022 at 22:19, Kamal Dasu <kdasu.kdev at gmail.com> wrote:
> >
> > From: Al Cooper <alcooperx at gmail.com>
> >
> > The 72116B0 has improved SDIO controllers that allow the max clock
> > rate to be increased from a max of 100MHz to a max of 150MHz. The
> > driver will need to get the clock and increase it's default rate
> > and override the caps register, that still indicates a max of 100MHz.
> > The new clock will be named "sdio_freq" in the DT node's "clock-names"
> > list. The driver will use a DT property, "clock-frequency", to
>
> /s/clock-frequency/max-frequency
>
>
> > enable this functionality and will get the actual rate in MHz
> > from the property to allow various speeds to be requested.
> >
> > Signed-off-by: Al Cooper <alcooperx at gmail.com>
> > Signed-off-by: Kamal Dasu <kdasu.kdev at gmail.com>
> > ---
> >  drivers/mmc/host/sdhci-brcmstb.c | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> >
> > diff --git a/drivers/mmc/host/sdhci-brcmstb.c b/drivers/mmc/host/sdhci-brcmstb.c
> > index 8eb57de48e0c..a1ffdd3f1640 100644
> > --- a/drivers/mmc/host/sdhci-brcmstb.c
> > +++ b/drivers/mmc/host/sdhci-brcmstb.c
> > @@ -250,6 +250,9 @@ static int sdhci_brcmstb_probe(struct platform_device *pdev)
> >         struct sdhci_pltfm_host *pltfm_host;
> >         const struct of_device_id *match;
> >         struct sdhci_brcmstb_priv *priv;
> > +       struct clk *master_clk;
> > +       u32 base_clock_hz = 0;
> > +       u32 actual_clock_mhz;
> >         struct sdhci_host *host;
> >         struct resource *iomem;
> >         struct clk *clk;
> > @@ -330,6 +333,33 @@ static int sdhci_brcmstb_probe(struct platform_device *pdev)
> >         if (match_priv->flags & BRCMSTB_MATCH_FLAGS_BROKEN_TIMEOUT)
> >                 host->quirks |= SDHCI_QUIRK_BROKEN_TIMEOUT_VAL;
> >
> > +       /* Change the base clock frequency if the DT property exists */
> > +       if (device_property_read_u32(&pdev->dev, "max-frequency",
> > +                                    &base_clock_hz) != 0)
> > +               goto add_host;
>
> The max-frequency DT property is already being parsed by
> mmc_of_parse() and the value is put in host->mmc->f_max. You could
> probably use that instead, right?
>
> > +
> > +       master_clk = devm_clk_get(&pdev->dev, "sdio_freq");
> > +       if (IS_ERR(master_clk)) {
> > +               dev_warn(&pdev->dev, "Clock for \"sdio_freq\" not found\n");
> > +               goto add_host;
> > +       } else {
> > +               res = clk_prepare_enable(master_clk);
> > +               if (res)
> > +                       goto err;
> > +       }
> > +
> > +       /* set improved clock rate */
> > +       clk_set_rate(master_clk, base_clock_hz);
> > +       actual_clock_mhz = clk_get_rate(master_clk) / 1000000;
> > +
> > +       host->caps &= ~SDHCI_CLOCK_V3_BASE_MASK;
> > +       host->caps |= (actual_clock_mhz << SDHCI_CLOCK_BASE_SHIFT);
> > +       /* Disable presets because they are now incorrect */
> > +       host->quirks2 |= SDHCI_QUIRK2_PRESET_VALUE_BROKEN;
> > +       dev_dbg(&pdev->dev, "Base Clock Frequency changed to %dMHz\n",
> > +               actual_clock_mhz);
> > +
> > +add_host:
> >         res = sdhci_brcmstb_add_host(host, priv);
> >         if (res)
> >                 goto err;
> > --
> > 2.17.1
> >
>
> Kind regards
> Uffe