linux-kernel - Re: [PATCH 11/13] devfreq: tegra30: Migrate to dev_pm_opp_set

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Message-ID: <20210122062659.qss3hef4kltfgciu@vireshk-i7>
Date:   Fri, 22 Jan 2021 11:56:59 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Stephen Boyd <sboyd@...nel.org>, Nishanth Menon <nm@...com>,
        Sibi Sankar <sibis@...eaurora.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-tegra@...r.kernel.org
Subject: Re: [PATCH 11/13] devfreq: tegra30: Migrate to dev_pm_opp_set_opp()

On 22-01-21, 00:36, Dmitry Osipenko wrote:
> 21.01.2021 14:17, Viresh Kumar пишет:
> > dev_pm_opp_set_bw() is getting removed and dev_pm_opp_set_opp() should
> > be used instead. Migrate to the new API.
> > 
> > Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> > ---
> >  drivers/devfreq/tegra30-devfreq.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
> > index 117cad7968ab..d2477d7d1f66 100644
> > --- a/drivers/devfreq/tegra30-devfreq.c
> > +++ b/drivers/devfreq/tegra30-devfreq.c
> > @@ -647,7 +647,7 @@ static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
> >  		return PTR_ERR(opp);
> >  	}
> >  
> > -	ret = dev_pm_opp_set_bw(dev, opp);
> > +	ret = dev_pm_opp_set_opp(dev, opp);
> >  	dev_pm_opp_put(opp);
> >  
> >  	return ret;
> > 
> 
> This patch introduces a very serious change that needs to be fixed.
> 
> Now dev_pm_opp_set_opp() changes both clock rate and bandwidth, this is
> unacceptable for this driver because it shall not touch the clock rate.
> 
> I think dev_pm_opp_set_bw() can't be removed.

I am wondering here on what would be a better solution, do what you
said or introduce another helper like dev_pm_opp_clear_clk(), which
will make sure the OPP core doesn't play with device's clk.

-- 
viresh