Re: [PATCH v4 12/13] mmc: mmci: add explicit clk control

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On 28 May 2014 15:47,  <srinivas.kandagatla@xxxxxxxxxx> wrote:
> From: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
>
> On Controllers like Qcom SD card controller where cclk is mclk and mclk should
> be directly controlled by the driver.
>
> This patch adds support to control mclk directly in the driver, and also
> adds explicit_mclk_control flag in variant structure giving more flexibility
> to the driver.
>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> ---
>  drivers/mmc/host/mmci.c | 96 ++++++++++++++++++++++++++++++++-----------------
>  drivers/mmc/host/mmci.h |  2 ++
>  2 files changed, 65 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> index 202f2d5..6eb0a29 100644
> --- a/drivers/mmc/host/mmci.c
> +++ b/drivers/mmc/host/mmci.c
> @@ -72,6 +72,7 @@ static unsigned int fmax = 515633;
>   * @pwrreg_clkgate: MMCIPOWER register must be used to gate the clock
>   * @busy_detect: true if busy detection on dat0 is supported
>   * @pwrreg_nopower: bits in MMCIPOWER don't controls ext. power supply
> + * @explicit_mclk_control: enable explicit mclk control in driver.
>   */
>  struct variant_data {
>         unsigned int            clkreg;
> @@ -93,6 +94,7 @@ struct variant_data {
>         bool                    pwrreg_clkgate;
>         bool                    busy_detect;
>         bool                    pwrreg_nopower;
> +       bool                    explicit_mclk_control;
>  };
>
>  static struct variant_data variant_arm = {
> @@ -199,6 +201,7 @@ static struct variant_data variant_qcom = {
>         .datalength_bits        = 24,
>         .pwrreg_powerup         = MCI_PWR_UP,
>         .f_max                  = 208000000,
> +       .explicit_mclk_control  = true,

This should go in patch3 instead.

>  };
>
>  static int mmci_card_busy(struct mmc_host *mmc)
> @@ -301,7 +304,9 @@ static void mmci_set_clkreg(struct mmci_host *host, unsigned int desired)
>         host->cclk = 0;
>
>         if (desired) {
> -               if (desired >= host->mclk) {
> +               if (variant->explicit_mclk_control) {
> +                       host->cclk = host->mclk;
> +               } else if (desired >= host->mclk) {
>                         clk = MCI_CLK_BYPASS;
>                         if (variant->st_clkdiv)
>                                 clk |= MCI_ST_UX500_NEG_EDGE;
> @@ -1340,6 +1345,18 @@ static void mmci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>         if (!ios->clock && variant->pwrreg_clkgate)
>                 pwr &= ~MCI_PWR_ON;
>
> +       if ((host->variant->explicit_mclk_control) &&
> +           (ios->clock != host->mclk_req)) {
> +               int rc = clk_set_rate(host->clk, ios->clock);
> +               if (rc < 0) {
> +                       dev_err(mmc_dev(host->mmc),
> +                               "Error setting clock rate (%d)\n", rc);
> +               } else {
> +                       host->mclk = clk_get_rate(host->clk);
> +                       host->mclk_req = ios->clock;
> +               }
> +       }
> +
>         spin_lock_irqsave(&host->lock, flags);
>
>         mmci_set_clkreg(host, ios->clock);
> @@ -1490,19 +1507,6 @@ static int mmci_probe(struct amba_device *dev,
>         host->plat = plat;
>         host->variant = variant;
>         host->mclk = clk_get_rate(host->clk);
> -       /*
> -        * According to the spec, mclk is max 100 MHz,
> -        * so we try to adjust the clock down to this,
> -        * (if possible).
> -        */
> -       if (host->mclk > host->variant->f_max) {
> -               ret = clk_set_rate(host->clk, host->variant->f_max);
> -               if (ret < 0)
> -                       goto clk_disable;
> -               host->mclk = clk_get_rate(host->clk);
> -               dev_dbg(mmc_dev(mmc), "eventual mclk rate: %u Hz\n",
> -                       host->mclk);
> -       }

The above code is relevant for Qcom as well, I don't think you need
change/move it.

>
>         host->phybase = dev->res.start;
>         host->base = devm_ioremap_resource(&dev->dev, &dev->res);
> @@ -1511,25 +1515,51 @@ static int mmci_probe(struct amba_device *dev,
>                 goto clk_disable;
>         }
>
> -       /*
> -        * The ARM and ST versions of the block have slightly different
> -        * clock divider equations which means that the minimum divider
> -        * differs too.
> -        */
> -       if (variant->st_clkdiv)
> -               mmc->f_min = DIV_ROUND_UP(host->mclk, 257);

I think you could simplify the change of fixing with f_min and f_max.

Start by, just add another statement here "else if
(variant->explicit_mclk_control)" and do the clk_round_rate()

> -       else
> -               mmc->f_min = DIV_ROUND_UP(host->mclk, 512);
> -       /*
> -        * If no maximum operating frequency is supplied, fall back to use
> -        * the module parameter, which has a (low) default value in case it
> -        * is not specified. Either value must not exceed the clock rate into
> -        * the block, of course.
> -        */
> -       if (mmc->f_max)
> -               mmc->f_max = min(host->mclk, mmc->f_max);
> -       else
> -               mmc->f_max = min(host->mclk, fmax);

Further replace the above with:
if (mmc->f_max)
     mmc->f_max = variant->explicit_mclk_control ? min(mmc->f_max,
variant->f_max) : min(host->mclk, mmc->f_max);
else
     mmc->f_max = variant->explicit_mclk_control ? fmax : min(host->mclk, fmax);

That should do it, right?

> +       if (variant->explicit_mclk_control) {
> +               /* get the nearest minimum clock to 100Khz */
> +               mmc->f_min = clk_round_rate(host->clk, 100000);
> +
> +               if (mmc->f_max)
> +                       mmc->f_max = min(host->variant->f_max, mmc->f_max);
> +               else
> +                       mmc->f_max = min(host->variant->f_max, fmax);
> +
> +       } else {
> +               /*
> +                * According to the spec, mclk is max 100 MHz,
> +                * so we try to adjust the clock down to this,
> +                * (if possible).
> +                */
> +               if (host->mclk > host->variant->f_max) {
> +                       ret = clk_set_rate(host->clk, host->variant->f_max);
> +                       if (ret < 0)
> +                               goto clk_disable;
> +                       host->mclk = clk_get_rate(host->clk);
> +                       dev_dbg(mmc_dev(mmc), "eventual mclk rate: %u Hz\n",
> +                               host->mclk);
> +               }
> +               /*
> +                * The ARM and ST versions of the block have slightly different
> +                * clock divider equations which means that the minimum divider
> +                * differs too.
> +                */
> +               if (variant->st_clkdiv)
> +                       mmc->f_min = DIV_ROUND_UP(host->mclk, 257);
> +               else
> +                       mmc->f_min = DIV_ROUND_UP(host->mclk, 512);
> +               /*
> +                * If no maximum operating frequency is supplied, fall back to
> +                * use the module parameter, which has a (low) default value in
> +                * case it is not specified. Either value must not exceed the
> +                * clock rate into the block, of course.
> +                */
> +               if (mmc->f_max)
> +                       mmc->f_max = min(host->mclk, mmc->f_max);
> +               else
> +                       mmc->f_max = min(host->mclk, fmax);
> +
> +       }
> +
>         dev_dbg(mmc_dev(mmc), "clocking block at %u Hz\n", mmc->f_max);
>
>         /* Get regulators and the supported OCR mask */
> diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
> index 706eb513..1882e20 100644
> --- a/drivers/mmc/host/mmci.h
> +++ b/drivers/mmc/host/mmci.h
> @@ -208,6 +208,8 @@ struct mmci_host {
>         spinlock_t              lock;
>
>         unsigned int            mclk;
> +       /* cached value of requested clk in set_ios */
> +       unsigned int            mclk_req;

How about "clock_cache" instead?

>         unsigned int            cclk;
>         u32                     pwr_reg;
>         u32                     pwr_reg_add;
> --
> 1.9.1
>

Kind regards
Ulf Hansson
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