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

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Message-ID: <20200128213336.GH46072@google.com>
Date:   Tue, 28 Jan 2020 13:33:36 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Sibi Sankar <sibis@...eaurora.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

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'?

> + * @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;

> +	}
> +
> +	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).