[PATCH v12 1/6] ARM: sunxi: Add driver for SD/MMC hosts found on Allwinner sunxi SoCs

[Ulf Hansson]

On 12 May 2014 13:20, Hans de Goede <hdegoede at redhat.com> wrote:
> Hi,
>
> On 05/12/2014 11:15 AM, Ulf Hansson wrote:
>> On 11 May 2014 09:46, Hans de Goede <hdegoede at redhat.com> wrote:
>>> From: David Lanzendörfer <david.lanzendoerfer at o2s.ch>
>>>
>>> The Allwinner sunxi mmc host uses dma in bus-master mode using a built-in
>>> designware idmac controller, which is identical to the one found in the mmc-dw
>>> hosts. However the rest of the host is not identical to mmc-dw, it deals with
>>> sending stop commands in hardware which makes it significantly different
>>> from the mmc-dw devices.
>>>
>>> HdG: Various cleanups and fixes.
>>>
>>> Signed-off-by: David Lanzendörfer <david.lanzendoerfer at o2s.ch>
>>> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
>>
>> [snip]
>>
>>> +
>>> +static int sunxi_mmc_clk_set_rate(struct sunxi_mmc_host *host,
>>> +                                 struct mmc_ios *ios)
>>> +{
>>> +       u32 rate, oclk_dly, rval, sclk_dly, src_clk;
>>> +       struct clk_hw *hw = __clk_get_hw(host->clk_mmc);
>>
>> Hi Hans,
>>
>> This seems like the wrong approach. But I guess it's related to the
>> "clock phase control" API you have been discussing with the clk
>> maintainer, Mike Turquette!?
>
> Yes, this is meant as a temporary solution until we get a proper
> "clock phase control" API.
>
>>
>> __clk_get_hw is supposed to be used by clk providers, not clk consumers.
>>
>>> +       int ret;
>>> +
>>> +       rate = clk_round_rate(host->clk_mmc, ios->clock);
>>> +       dev_dbg(mmc_dev(host->mmc), "setting clk to %d, rounded %d\n",
>>> +               ios->clock, rate);
>>> +
>>> +       /* setting clock rate */
>>> +       ret = clk_set_rate(host->clk_mmc, rate);
>>> +       if (ret) {
>>> +               dev_err(mmc_dev(host->mmc), "error setting clk to %d: %d\n",
>>> +                       rate, ret);
>>> +               return ret;
>>> +       }
>>> +
>>> +       ret = sunxi_mmc_oclk_onoff(host, 0);
>>> +       if (ret)
>>> +               return ret;
>>> +
>>> +       /* clear internal divider */
>>> +       rval = mmc_readl(host, REG_CLKCR);
>>> +       rval &= ~0xff;
>>> +       mmc_writel(host, REG_CLKCR, rval);
>>> +
>>> +       /* determine delays */
>>> +       if (rate <= 400000) {
>>> +               oclk_dly = 0;
>>> +               sclk_dly = 7;
>>> +       } else if (rate <= 25000000) {
>>> +               oclk_dly = 0;
>>> +               sclk_dly = 5;
>>> +       } else if (rate <= 50000000) {
>>> +               if (ios->timing == MMC_TIMING_UHS_DDR50) {
>>> +                       oclk_dly = 2;
>>> +                       sclk_dly = 4;
>>> +               } else {
>>> +                       oclk_dly = 3;
>>> +                       sclk_dly = 5;
>>> +               }
>>> +       } else {
>>> +               /* rate > 50000000 */
>>> +               oclk_dly = 2;
>>> +               sclk_dly = 4;
>>> +       }
>>> +
>>> +       src_clk = clk_get_rate(clk_get_parent(host->clk_mmc));
>>> +       if (src_clk >= 300000000 && src_clk <= 400000000) {
>>> +               if (oclk_dly)
>>> +                       oclk_dly--;
>>> +               if (sclk_dly)
>>> +                       sclk_dly--;
>>> +       }
>>> +
>>> +       clk_sunxi_mmc_phase_control(hw, sclk_dly, oclk_dly);
>>> +
>>> +       return sunxi_mmc_oclk_onoff(host, 1);
>>> +}
>>> +
>>
>> [snip]
>>
>> Besides the above, I think this looks good!
>
> Thanks!
>
> Since Mike Turquette has already merged clk_sunxi_mmc_phase_control
> I would like to keep this as is, as I already promised Mike, I can
> safely promise you too: I promise clean this up as soon as the
> "clock phase control" API has been worked out.

Thanks for promise. :-)

Anyway, I think I would like Mike to confirm this violation is
accepted as a temporary solution. Additionally I would like it to be
commented in the code here, that it's a temporary solution and that it
violates the clk API.

Kind regards
Ulf Hansson

>
> Regards,
>
> Hans