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

[Ritesh Harjani <riteshh@codeaurora.org>]

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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