linux-kernel - Re: [v4, 6/8] PM / OPP: Support adjusting OPP voltages at runtime

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Date:   Mon, 19 Aug 2019 16:48:36 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Andrew-sh.Cheng" <andrew-sh.cheng@...iatek.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        srv_heupstream@...iatek.com, fan.chen@...iatek.com,
        Stephen Boyd <sboyd@...eaurora.org>,
        Roger Lu <roger.lu@...iatek.com>
Subject: Re: [v4, 6/8] PM / OPP: Support adjusting OPP voltages at runtime

On 13-08-19, 21:31, Andrew-sh.Cheng wrote:
> From: Stephen Boyd <sboyd@...eaurora.org>
> 
> On some SoCs the Adaptive Voltage Scaling (AVS) technique is
> employed to optimize the operating voltage of a device. At a
> given frequency, the hardware monitors dynamic factors and either
> makes a suggestion for how much to adjust a voltage for the
> current frequency, or it automatically adjusts the voltage
> without software intervention. Add an API to the OPP library for
> the former case, so that AVS type devices can update the voltages
> for an OPP when the hardware determines the voltage should
> change. The assumption is that drivers like CPUfreq or devfreq
> will register for the OPP notifiers and adjust the voltage
> according to suggestions that AVS makes.
> 
> This patch is devired from [1] submitted by Stephen.
> [1] https://lore.kernel.org/patchwork/patch/599279/
> 
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> Signed-off-by: Roger Lu <roger.lu@...iatek.com>
> ---
>  drivers/opp/core.c     | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pm_opp.h | 11 +++++++++
>  2 files changed, 74 insertions(+)
> 
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index c094d5d20fd7..407a07f29b12 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -2054,6 +2054,69 @@ static int _opp_set_availability(struct device *dev, unsigned long freq,
>  }
>  
>  /**
> + * dev_pm_opp_adjust_voltage() - helper to change the voltage of an OPP
> + * @dev:		device for which we do this operation
> + * @freq:		OPP frequency to adjust voltage of
> + * @u_volt:		new OPP voltage
> + *
> + * Return: -EINVAL for bad pointers, -ENOMEM if no memory available for the
> + * copy operation, returns 0 if no modifcation was done OR modification was
> + * successful.
> + */
> +int dev_pm_opp_adjust_voltage(struct device *dev, unsigned long freq,
> +			      unsigned long u_volt)

Can you please update this to take a triplet instead ? That is what we are
storing in OPP core now a days.

-- 
viresh