Re: [PATCH v7 08/14] mmc: sdhci-msm: Implement set_clock callback for sdhci-msm

[Ritesh Harjani <riteshh@xxxxxxxxxxxxxx>]

On 11/16/2016 1:12 PM, Adrian Hunter wrote:
> On 16/11/16 06:42, Ritesh Harjani wrote:
> > Hi,
> >
> > On 11/15/2016 10:40 AM, Ritesh Harjani wrote:
> > > Hi Stephen/Adrian,
> > >
> > > On 11/15/2016 1:07 AM, Stephen Boyd wrote:
> > > > On 11/14, Ritesh Harjani wrote:
> > > > > @@ -577,6 +578,90 @@ static unsigned int
> > > > > sdhci_msm_get_min_clock(struct sdhci_host *host)
> > > > >      return SDHCI_MSM_MIN_CLOCK;
> > > > >  }
> > > > >
> > > > > +/**
> > > > > + * __sdhci_msm_set_clock - sdhci_msm clock control.
> > > > > + *
> > > > > + * Description:
> > > > > + * Implement MSM version of sdhci_set_clock.
> > > > > + * This is required since MSM controller does not
> > > > > + * use internal divider and instead directly control
> > > > > + * the GCC clock as per HW recommendation.
> > > > > + **/
> > > > > +void __sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
> > > > > +{
> > > > > +    u16 clk;
> > > > > +    unsigned long timeout;
> > > > > +
> > > > > +    /*
> > > > > +     * Keep actual_clock as zero -
> > > > > +     * - since there is no divider used so no need of having
> > > > > actual_clock.
> > > > > +     * - MSM controller uses SDCLK for data timeout calculation. If
> > > > > +     *   actual_clock is zero, host->clock is taken for calculation.
> > > > > +     */
> > > > > +    host->mmc->actual_clock = 0;
> > > > > +
> > > > > +    sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
> > > > > +
> > > > > +    if (clock == 0)
> > > > > +        return;
> > > > > +
> > > > > +    /*
> > > > > +     * MSM controller do not use clock divider.
> > > > > +     * Thus read SDHCI_CLOCK_CONTROL and only enable
> > > > > +     * clock with no divider value programmed.
> > > > > +     */
> > > > > +    clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> > > > > +
> > > > > +    clk |= SDHCI_CLOCK_INT_EN;
> > > > > +    sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> > > > > +
> > > > > +    /* Wait max 20 ms */
> > > > > +    timeout = 20;
> > > > > +    while (!((clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
> > > > > +        & SDHCI_CLOCK_INT_STABLE)) {
> > > > > +        if (timeout == 0) {
> > > > > +            pr_err("%s: Internal clock never stabilised\n",
> > > > > +                   mmc_hostname(host->mmc));
> > > > > +            return;
> > > > > +        }
> > > > > +        timeout--;
> > > > > +        mdelay(1);
> > > > > +    }
> > > > > +
> > > > > +    clk |= SDHCI_CLOCK_CARD_EN;
> > > > > +    sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> > > >
> > > > This is almost a copy/paste of sdhci_set_clock(). Can we make
> > > > sdhci_set_clock() call a __sdhci_set_clock() function that takes
> > > > unsigned int clock, and also a flag indicating if we want to set
> > > > the internal clock divider or not? Then we can call
> > > > __sdhci_set_clock() from sdhci_set_clock() with (clock, true) as
> > > > arguments and (clock, false).
> > Actually what you may be referring here is some sort of quirks which is not
> > entertained any more for sdhci driver.
> > sdhci is tending towards becoming a library and hence such changes are
> > restricted.
> >
> > But I think we may do below changes to avoid duplication of code which
> > enables the sdhci internal clock and waits for internal clock to be stable.
> >
> > Adrian, could you please tell if this should be ok?
>
> That seems fine, but the name seems too long - how about changing
> sdhci_set_clock_enable to sdhci_enable_clk.
Sure. Will make the changes then.

> > Then we may be able to call for sdhci_set_clock_enable function from
> > sdhci_msm_set_clock.
> >
> >
> > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> > index 42ef3eb..28e605c 100644
> > --- a/drivers/mmc/host/sdhci.c
> > +++ b/drivers/mmc/host/sdhci.c
> > @@ -1343,19 +1343,8 @@ u16 sdhci_calc_clk(struct sdhci_host *host, unsigned
> > int clock,
> >  }
> >  EXPORT_SYMBOL_GPL(sdhci_calc_clk);
> >
> > -void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
> > +void sdhci_set_clock_enable(struct sdhci_host *host, unsigned short clk)
> >  {
> > -       u16 clk;
> > -       unsigned long timeout;
> > -
> > -       host->mmc->actual_clock = 0;
> > -
> > -       sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
> > -
> > -       if (clock == 0)
> > -               return;
> > -
> > -       clk = sdhci_calc_clk(host, clock, &host->mmc->actual_clock);
> >
> >         clk |= SDHCI_CLOCK_INT_EN;
> >         sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> > @@ -1377,6 +1366,24 @@ void sdhci_set_clock(struct sdhci_host *host,
> > unsigned int clock)
> >         clk |= SDHCI_CLOCK_CARD_EN;
> >         sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> >  }
> > +EXPORT_SYMBOL_GPL(sdhci_set_clock_enable);
> > +
> > +void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
> > +{
> > +       u16 clk;
> > +       unsigned long timeout;
> > +
> > +       host->mmc->actual_clock = 0;
> > +
> > +       sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
> > +
> > +       if (clock == 0)
> > +               return;
> > +
> > +       clk = sdhci_calc_clk(host, clock, &host->mmc->actual_clock);
> > +
> > +       sdhci_set_clock_enable(host, clk);
> > +}
> >  EXPORT_SYMBOL_GPL(sdhci_set_clock);
> >
> >  static void sdhci_set_power_reg(struct sdhci_host *host, unsigned char mode,
> > diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> > index 766df17..43382e1 100644
> > --- a/drivers/mmc/host/sdhci.h
> > +++ b/drivers/mmc/host/sdhci.h
> > @@ -681,6 +681,7 @@ static inline bool sdhci_sdio_irq_enabled(struct
> > sdhci_host *host)
> >  u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock,
> >                    unsigned int *actual_clock);
> >  void sdhci_set_clock(struct sdhci_host *host, unsigned int clock);
> > +void sdhci_set_clock_enable(struct sdhci_host *host, unsigned short clk);
> >  void sdhci_set_power(struct sdhci_host *host, unsigned char mode,
> >                      unsigned short vdd);
> >  void sdhci_set_power_noreg(struct sdhci_host *host, unsigned char mode,
> >
> >
> >
> > > Adrian,
> > > Could you please comment here ?
> > >
> > > > > +}
> > > > > +
> > > > > +/* sdhci_msm_set_clock - Called with (host->lock) spinlock held. */
> > > > > +static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned
> > > > > int clock)
> > > > > +{
> > > > > +    struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> > > > > +    struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> > > > > +    int rc;
> > > > > +
> > > > > +    if (!clock) {
> > > > > +        msm_host->clk_rate = clock;
> > > > > +        goto out;
> > > > > +    }
> > > > > +
> > > > > +    spin_unlock_irq(&host->lock);
> > > > > +    if (clock != msm_host->clk_rate) {
> > > >
> > > > Why do we need to check here? Can't we call clk_set_rate()
> > > > Unconditionally?
> > > Since it may so happen that above layers may call for ->set_clock
> > > function with same requested clock more than once, hence we cache the
> > > host->clock here.
> > > Also, since requested clock (host->clock) can be say 400Mhz but the
> > > actual pltfm supported clock would be say 384MHz.
> > >
> > >
> > > > > +        rc = clk_set_rate(msm_host->clk, clock);
> > > > > +        if (rc) {
> > > > > +            pr_err("%s: Failed to set clock at rate %u\n",
> > > > > +                   mmc_hostname(host->mmc), clock);
> > > > > +            spin_lock_irq(&host->lock);
> > > > > +            goto out;
> > > >
> > > > Or replace the above two lines with goto err;
> > > Ok, I will have another label out_lock instead of err.
> > > > > +        }
> > > > > +        msm_host->clk_rate = clock;
> > > > > +        pr_debug("%s: Setting clock at rate %lu\n",
> > > > > +             mmc_hostname(host->mmc), clk_get_rate(msm_host->clk));
> > > > > +    }
> > > >
> > > > And put an err label here.
> > > will put the label here as out_lock;
> > > > > +    spin_lock_irq(&host->lock);
> > > > > +out:
> > > > > +    __sdhci_msm_set_clock(host, clock);
> > > > > +}
> > > > > +
> > > > >  static const struct of_device_id sdhci_msm_dt_match[] = {
> > > > >      { .compatible = "qcom,sdhci-msm-v4" },
> > > > >      {},

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