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

[Ritesh Harjani <riteshh@codeaurora.org>]

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).
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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