linux-kernel - Re: [RFC v3 04/10] OPP: Add and export helper to update voltage

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Date:   Wed, 29 Jan 2020 19:19:47 +0530
From:   Sibi Sankar <sibis@...eaurora.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     viresh.kumar@...aro.org, sboyd@...nel.org,
        georgi.djakov@...aro.org, saravanak@...gle.com, nm@...com,
        bjorn.andersson@...aro.org, agross@...nel.org,
        david.brown@...aro.org, robh+dt@...nel.org, mark.rutland@....com,
        rjw@...ysocki.net, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, dianders@...omium.org,
        vincent.guittot@...aro.org, amit.kucheria@...aro.org,
        ulf.hansson@...aro.org
Subject: Re: [RFC v3 04/10] OPP: Add and export helper to update voltage

On 2020-01-29 03:03, Matthias Kaehlcke wrote:
> Hi Sibi,
> 
> On Tue, Jan 28, 2020 at 01:33:44AM +0530, Sibi Sankar wrote:
>> Add and export 'dev_pm_opp_update_voltage' to find and update voltage
>> of an opp for a given frequency. This will be useful to update the 
>> opps
>> with voltages read back from firmware.
>> 
>> Signed-off-by: Sibi Sankar <sibis@...eaurora.org>
>> ---
>>  drivers/opp/core.c     | 55 
>> ++++++++++++++++++++++++++++++++++++++++++
>>  include/linux/pm_opp.h | 10 ++++++++
>>  2 files changed, 65 insertions(+)
>> 
>> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
>> index 9aa2a44a5d638..f241e83ec926a 100644
>> --- a/drivers/opp/core.c
>> +++ b/drivers/opp/core.c
>> @@ -2503,6 +2503,61 @@ int dev_pm_opp_disable(struct device *dev, 
>> unsigned long freq)
>>  }
>>  EXPORT_SYMBOL_GPL(dev_pm_opp_disable);
>> 
>> +/**
>> + * dev_pm_opp_update_voltage() - Find and update voltage
> 
> The comment should mention that this is done for an OPP.
> 
> Maybe omit the 'find' part here and just say 'Update the voltage of
> an OPP'?

sure makes sense

> 
>> + * @dev:	device for which we do this operation
>> + * @freq:	OPP frequency to update voltage
>> + * @u_volt:	voltage requested for this opp
>> + *
>> + * Find and update voltage of a disabled opp corresponding to the 
>> given
>> + * frequency. This is useful only for devices with single power 
>> supply.
>> + *
>> + * Return: 0 if modification was successful or a negative error 
>> value.
>> + */
>> +int dev_pm_opp_update_voltage(struct device *dev, unsigned long freq,
>> +			      unsigned long u_volt)
>> +{
>> +	struct dev_pm_opp *opp = ERR_PTR(-ENODEV);
> 
> initialization is not needed
> 
>> +	struct opp_table *opp_table;
>> +	unsigned long tol;
>> +	int ret = 0;
>> +
>> +	/* Find the opp_table */
> 
> Drop the comment, it's obvious from the code.
> 
>> +	opp_table = _find_opp_table(dev);
>> +	if (IS_ERR(opp_table)) {
>> +		ret = PTR_ERR(opp_table);
>> +		dev_err(dev, "%s: OPP table not found (%d)\n", __func__, ret);
>> +		return PTR_ERR(opp_table);
> 
>   		return ret;

missed that :(

> 
>> +	}
>> +
>> +	opp = dev_pm_opp_find_freq_exact(dev, freq, false);
>> +	if (IS_ERR(opp)) {
>> +		ret = PTR_ERR(opp);
>> +		goto put_table;
>> +	}
>> +
>> +	mutex_lock(&opp_table->lock);
>> +
>> +	/* update only if the opp is disabled */
>> +	if (opp->available) {
>> +		ret = -EBUSY;
>> +		goto unlock;
>> +	}
>> +
>> +	tol = u_volt * opp_table->voltage_tolerance_v1 / 100;
>> +	opp->supplies[0].u_volt_min = u_volt - tol;
>> +	opp->supplies[0].u_volt = u_volt;
>> +	opp->supplies[0].u_volt_min = u_volt + tol;
> 
>   			.u_volt_max =
> 
> I suppose the assignments need to be done for all possible supplies,
> i.e. 0 to (opp_table->regulator_count - 1).

a single value for all possible
supplies seems wrong. Anyway
will wait to see what Viresh
thinks about it.

-- 
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