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Date:   Fri, 22 May 2020 18:57:23 +0530
From:   Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     adrian.hunter@...el.com, ulf.hansson@...aro.org,
        robh+dt@...nel.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, Asutosh Das <asutoshd@...eaurora.org>,
        Vijay Viswanath <vviswana@...eaurora.org>,
        Andy Gross <agross@...nel.org>
Subject: Re: [PATCH V2 2/3] mmc: sdhci-msm: Use internal voltage control

Hi Bjorn,

On 5/22/2020 12:37 AM, Bjorn Andersson wrote:
> On Thu 21 May 08:23 PDT 2020, Veerabhadrarao Badiganti wrote:
>
>> On qcom SD host controllers voltage switching be done after the HW
>> is ready for it. The HW informs its readiness through power irq.
>> The voltage switching should happen only then.
>>
>> Use the internal voltage switching and then control the voltage
>> switching using power irq.
>>
>> Set the regulator load as well so that regulator can be configured
>> in LPM mode when in is not being used.
>>
>> Co-developed-by: Asutosh Das <asutoshd@...eaurora.org>
>> Signed-off-by: Asutosh Das <asutoshd@...eaurora.org>
>> Co-developed-by: Vijay Viswanath <vviswana@...eaurora.org>
>> Signed-off-by: Vijay Viswanath <vviswana@...eaurora.org>
>> Co-developed-by: Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
>> Signed-off-by: Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
> Looks better, thanks.
>
>> ---
>>   drivers/mmc/host/sdhci-msm.c | 207 +++++++++++++++++++++++++++++++++++++++++--
>>   1 file changed, 198 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> [..]
>>   static const struct sdhci_msm_offset *sdhci_priv_msm_offset(struct sdhci_host *host)
>> @@ -1298,6 +1302,71 @@ static void sdhci_msm_set_uhs_signaling(struct sdhci_host *host,
>>   		sdhci_msm_hs400(host, &mmc->ios);
>>   }
>>   
>> +static int sdhci_msm_set_vmmc(struct mmc_host *mmc)
>> +{
>> +	int ret;
>> +
>> +	if (IS_ERR(mmc->supply.vmmc))
>> +		return 0;
>> +
>> +	ret = mmc_regulator_set_ocr(mmc, mmc->supply.vmmc, mmc->ios.vdd);
>> +	if (ret)
>> +		dev_err(mmc_dev(mmc), "%s: vmmc set ocr with vdd=%d failed: %d\n",
>> +			mmc_hostname(mmc), mmc->ios.vdd, ret);
> Missed this one on v1, in the event that mmc_regulator_set_ocr() return
> a non-zero value it has already printed an error message. So please
> replace the tail with just:
>
> 	return mmc_regulator_set_ocr(...);
>
>> +
>> +	return ret;
>> +}
>> +
>> +static int sdhci_msm_set_vqmmc(struct sdhci_msm_host *msm_host,
>> +			      struct mmc_host *mmc, bool level)
>> +{
>> +	int load, ret;
>> +	struct mmc_ios ios;
>> +
>> +	if (IS_ERR(mmc->supply.vqmmc)			 ||
>> +	    (mmc->ios.power_mode == MMC_POWER_UNDEFINED) ||
>> +	    (msm_host->vqmmc_enabled == level))
>> +		return 0;
>> +
>> +	if (msm_host->vqmmc_load) {
>> +		load = level ? msm_host->vqmmc_load : 0;
>> +		ret = regulator_set_load(mmc->supply.vqmmc, load);
> Sorry for the late reply on v1, but please see my explanation regarding
> load and always-on regulators there.

<Merging your comment from V1 here>

 >> You should still call regulator_enable()/regulator_disable() on your
 >> consumer regulator in this driver. When you do this the regulator core
 >> will conclude that the regulator_dev (i.e. the part that represents the
 >> hardware) is marked always_on and will not enable/disable the regulator.

 >> But it will still invoke _regulator_handle_consumer_enable() and
 >> _regulator_handle_consumer_disable(), which will aggregate the "load" of
 >> all client regulators and update the regulator's load.

 >> So this will apply the load as you expect regardless of it being
 >> supplied by a regulator marked as always_on.

Since I'm not turning off this regulator for eMMC, I wanted to keep it 
in LPM mode
to save some power.
When the regulator configured in auto mode (RPMH_REGULATOR_MODE_AUTO) it
switches to LPM/HPM mode based on the active load.
So i have to minimize my driver load requirement so that I can let this 
regulator
in LPM mode.
So i need to set load every-time I disable/enable the regulator.

>> +		if (ret) {
>> +			dev_err(mmc_dev(mmc), "%s: vqmmc set load failed: %d\n",
>> +				mmc_hostname(mmc), ret);
>> +			goto out;
>> +		}
>> +	}
>> +
>> +	if (level) {
>> +		/* Set the IO voltage regulator to default voltage level */
>> +		if (msm_host->caps_0 & CORE_3_0V_SUPPORT)
>> +			ios.signal_voltage = MMC_SIGNAL_VOLTAGE_330;
>> +		else if (msm_host->caps_0 & CORE_1_8V_SUPPORT)
>> +			ios.signal_voltage = MMC_SIGNAL_VOLTAGE_180;
>> +
>> +		if (msm_host->caps_0 & CORE_VOLT_SUPPORT) {
>> +			ret = mmc_regulator_set_vqmmc(mmc, &ios);
>> +			if (ret < 0) {
>> +				dev_err(mmc_dev(mmc), "%s: vqmmc set volgate failed: %d\n",
>> +					mmc_hostname(mmc), ret);
>> +				goto out;
>> +			}
>> +		}
>> +		ret = regulator_enable(mmc->supply.vqmmc);
>> +	} else {
>> +		ret = regulator_disable(mmc->supply.vqmmc);
>> +	}
>> +
>> +	if (ret)
>> +		dev_err(mmc_dev(mmc), "%s: vqmm %sable failed: %d\n",
>> +			mmc_hostname(mmc), level ? "en":"dis", ret);
>> +	else
>> +		msm_host->vqmmc_enabled = level;
>> +out:
>> +	return ret;
>> +}
> [..]
>> +static int sdhci_msm_start_signal_voltage_switch(struct mmc_host *mmc,
>> +				      struct mmc_ios *ios)
>> +{
>> +	struct sdhci_host *host = mmc_priv(mmc);
>> +	u16 ctrl, status;
>> +
>> +	/*
>> +	 * Signal Voltage Switching is only applicable for Host Controllers
>> +	 * v3.00 and above.
>> +	 */
>> +	if (host->version < SDHCI_SPEC_300)
>> +		return 0;
>> +
>> +	ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>> +
>> +	switch (ios->signal_voltage) {
>> +	case MMC_SIGNAL_VOLTAGE_330:
>> +		if (!(host->flags & SDHCI_SIGNALING_330))
>> +			return -EINVAL;
>> +
>> +		/* Set 1.8V Signal Enable in the Host Control2 register to 0 */
>> +		ctrl &= ~SDHCI_CTRL_VDD_180;
>> +		break;
>> +	case MMC_SIGNAL_VOLTAGE_180:
>> +		if (!(host->flags & SDHCI_SIGNALING_180))
>> +			return -EINVAL;
>> +
>> +		/*
>> +		 * Enable 1.8V Signal Enable in the Host Control2
>> +		 * register
>> +		 */
>> +		ctrl |= SDHCI_CTRL_VDD_180;
>> +		break;
>> +	case MMC_SIGNAL_VOLTAGE_120:
>> +		if (!(host->flags & SDHCI_SIGNALING_120))
>> +			return -EINVAL;
>> +		return 0;
>> +	default:
>> +		/* No signal voltage switch required */
>> +		return 0;
>> +	}
>> +
>> +	sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
>> +
>> +	/* Wait for 5ms */
>> +	usleep_range(5000, 5500);
>> +
>> +	/* regulator output should be stable within 5 ms */
>> +	status = !!(ctrl & SDHCI_CTRL_VDD_180);
>> +	ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
>> +	if (!!(ctrl &  SDHCI_CTRL_VDD_180) == status)
> You should be able to drop the !! both here and when assigning status.
>
> Overall this looks neater, thanks for reworking it.
>
> Regards,
> Bjorn


Thanks

Veera

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