linux-kernel - Re: [RFC v2 01/11] OPP: Don't overwrite rounded clk rate

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Date:   Mon, 17 Jun 2019 09:20:58 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     swboyd@...omium.org, Rajendra Nayak <rnayak@...eaurora.org>,
        vincent.guittot@...aro.org, mturquette@...libre.com
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-spi@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-scsi@...r.kernel.org, ulf.hansson@...aro.org,
        dianders@...omium.org, rafael@...nel.org
Subject: Re: [RFC v2 01/11] OPP: Don't overwrite rounded clk rate

On 14-06-19, 10:57, Viresh Kumar wrote:
> Hmm, so this patch won't break anything and I am inclined to apply it again :)
> 
> Does anyone see any other issues with it, which I might be missing ?

I have updated the commit log a bit more to clarify on things, please let me
know if it looks okay.

    opp: Don't overwrite rounded clk rate
    
    The OPP table normally contains 'fmax' values corresponding to the
    voltage or performance levels of each OPP, but we don't necessarily want
    all the devices to run at fmax all the time. Running at fmax makes sense
    for devices like CPU/GPU, which have a finite amount of work to do and
    since a specific amount of energy is consumed at an OPP, its better to
    run at the highest possible frequency for that voltage value.
    
    On the other hand, we have IO devices which need to run at specific
    frequencies only for their proper functioning, instead of maximum
    possible frequency.
    
    The OPP core currently roundup to the next possible OPP for a frequency
    and select the fmax value. To support the IO devices by the OPP core,
    lets do the roundup to fetch the voltage or performance state values,
    but not use the OPP frequency value. Rather use the value returned by
    clk_round_rate().
    
    The current user, cpufreq, of dev_pm_opp_set_rate() already does the
    rounding to the next OPP before calling this routine and it won't
    have any side affects because of this change.
    
    Signed-off-by: Stephen Boyd <swboyd@...omium.org>
    Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
    [ Viresh: Massaged changelog and use temp_opp variable instead ]
    Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>


-- 
viresh