Re: [PATCH V2 2/3] mmc: sdhci-msm: Use internal voltage control

From: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
To: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: adrian.hunter@intel.com, ulf.hansson@linaro.org,
	robh+dt@kernel.org, linux-mmc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	devicetree@vger.kernel.org, Asutosh Das <asutoshd@codeaurora.org>,
	Vijay Viswanath <vviswana@codeaurora.org>,
	Andy Gross <agross@kernel.org>
Subject: Re: [PATCH V2 2/3] mmc: sdhci-msm: Use internal voltage control
Date: Thu, 28 May 2020 12:43:03 +0530	[thread overview]
Message-ID: <b2db3743-63bd-9a34-3fcb-d9faac96dfee@codeaurora.org> (raw)
In-Reply-To: <20200522170415.GI11847@yoga>


On 5/22/2020 10:34 PM, Bjorn Andersson wrote:
> On Fri 22 May 06:27 PDT 2020, Veerabhadrarao Badiganti wrote:
>
>> 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@codeaurora.org>
>>>> Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
>>>> Co-developed-by: Vijay Viswanath <vviswana@codeaurora.org>
>>>> Signed-off-by: Vijay Viswanath <vviswana@codeaurora.org>
>>>> Co-developed-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.org>
>>>> Signed-off-by: Veerabhadrarao Badiganti <vbadigan@codeaurora.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.
>>
> You call regulator_enable(vqmmc) and regulator_disable() below, so you
> are telling the regulator framework that your struct regulator should be
> "on" or "off".
>
> This will cause the sum of all struct regulator's for the underlying
> struct regulator_dev to be recalculated. So after calling
> regulator_disable() below your effective addition to the load
> calculation is 0, regardless of which load you have specified.
>
> Independent of this the property regulator-always-on (always_on in
> struct regulator_dev) will determine if the enable/disable request will
> actually be sent to the RPMh.
>
>
> So, if you where to not call regulator_disable() for eMMC your argument
> is correct, but as far as I can see you are and you're relying on the
> regulator core to keep it always-on - and then the load logic is in
> effect still.
Thanks for the details Bjorn.
My requirement is, for eMMC i shouldn't be turning this regulator off. 
But has to configure in LPM mode.
For SD-card, i have to turn-off this regulator.
So I'm planning to update the logic as below, let me know if you have 
any other suggestions.

+static int sdhci_msm_set_vqmmc(struct sdhci_msm_host *msm_host,
+                             struct mmc_host *mmc, bool level)
+{
+       int ret;
+       bool always_on;
+
+       if (IS_ERR(mmc->supply.vqmmc)           ||
+           (mmc->ios.power_mode == MMC_POWER_UNDEFINED))
+               return 0;
+       /*
+        * For eMMC don't turn off Vqmmc, Instead just configure it in LPM
+        * and HPM modes by setting the right amount of load.
+        */
+       always_on = mmc->card && mmc_card_mmc(mmc->card);
+
+       if (always_on)
+               ret = msm_config_vqmmc_mode(msm_host, mmc, level);
+       else
+               ret = msm_toggle_vqmmc(msm_host, mmc, level);
+
+       return ret;
+}
> Regards,
> Bjorn
>
>>>> +		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;
>>>> +}