linux-kernel - Re: [PATCH v2 20/20] cpufreq: Return zero on success in boost sw setting

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Message-ID: <a8dfa493-f858-e35d-7e57-78478be555c4@intel.com>
Date:   Mon, 18 May 2020 11:53:22 +0200
From:   "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Serge Semin <fancer.lancer@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Paul Burton <paulburton@...nel.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Arnd Bergmann <arnd@...db.de>,
        Rob Herring <robh+dt@...nel.org>, linux-mips@...r.kernel.org,
        devicetree@...r.kernel.org, stable@...r.kernel.org,
        Frederic Weisbecker <frederic@...nel.org>,
        Ingo Molnar <mingo@...nel.org>, Yue Hu <huyue2@...ong.com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 20/20] cpufreq: Return zero on success in boost sw
 setting

On 5/18/2020 9:41 AM, Viresh Kumar wrote:
> On 16-05-20, 15:52, Serge Semin wrote:
>> On Fri, May 15, 2020 at 05:58:47PM +0200, Rafael J. Wysocki wrote:
>>>> @@ -2554,7 +2554,7 @@ static int cpufreq_boost_set_sw(int state)
>>>>    			break;
>>>>    	}
>>>> -	return ret;
>>>> +	return ret < 0 ? ret : 0;
>>>>    }
>>>>    int cpufreq_boost_trigger_state(int state)
>>> IMO it is better to update the caller of this function to handle the
>>> positive value possibly returned by it correctly.
>> Could you elaborate why? Viresh seems to be ok with this solution.
> And it is absolutely fine for Rafael to not agree with it :)
>
>> As I see it the caller doesn't expect the positive value returned by the
>> original freq_qos_update_request(). It just doesn't need to know whether the
>> effective policy has been updated or not, it only needs to make sure the
>> operations has been successful. Moreover the positive value is related only
>> to the !last! active policy, which doesn't give the caller a full picture
>> of the policy change anyway. So taking all of these into account I'd leave the
>> fix as is.
> Rafael: This function is called via a function pointer, which can call
> this or a platform dependent routine (like in acpi-cpufreq.c), and it
> would be reasonable IMO for the return of that callback to only look
> for 0 or negative values, as is generally done in the kernel.

But it only has one caller that can easily check ret < 0 instead of just 
ret, so the extra branch can be saved.

That said if you really only want it to return 0 on success, you may as 
well add a ret = 0; statement (with a comment explaining why it is 
needed) after the last break in the loop.

Cheers!