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Date:   Fri, 22 May 2020 10:04:15 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Veerabhadrarao Badiganti <vbadigan@...eaurora.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

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@...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.
> 

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.

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;
> > > +}

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