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

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Date:   Fri, 22 Jan 2021 18:28:16 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
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()

22.01.2021 09:26, Viresh Kumar пишет:
> 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.
> 

Either way will work, but maybe keeping the dev_pm_opp_set_bw() is a bit
more straightforward variant for now since it will avoid the code's
changes and it's probably a bit more obvious variant for the OPP users.