linux-kernel - RE: [PATCH] cpufreq: imx6q: Disable only available frequencies

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Message-ID: <a377e725107341a8bf57b5aaf63f058b@dh-electronics.com>
Date:   Thu, 11 May 2023 20:51:33 +0000
From:   Christoph Niedermaier <cniedermaier@...electronics.com>
To:     Marek Vasut <marex@...x.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
CC:     Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <festevam@...x.de>,
        NXP Linux Team <linux-imx@....com>,
        "open list:CPU FREQUENCY SCALING FRAMEWORK" 
        <linux-pm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] cpufreq: imx6q: Disable only available frequencies

From: Marek Vasut [mailto:marex@...x.de]
Sent: Thursday, May 11, 2023 9:26 PM
> On 5/11/23 11:23, Christoph Niedermaier wrote:
>> In the example in Documentation/power/opp.rst, an availability check
>> is present before disabling a specific frequency. If a frequency isn't
>> available, the warning of a failed disabling of a non-existent
>> frequency is misleading. Therefore, check the availability of the
>> frequency in a separate inline function before disabling it.
> 
> [...]
> 
>> diff --git a/drivers/cpufreq/imx6q-cpufreq.c b/drivers/cpufreq/imx6q-cpufreq.c
>> index 48e1772e98fd..4e2d2bc47aba 100644
>> --- a/drivers/cpufreq/imx6q-cpufreq.c
>> +++ b/drivers/cpufreq/imx6q-cpufreq.c
>> @@ -209,6 +209,21 @@ static struct cpufreq_driver imx6q_cpufreq_driver = {
>>       .suspend = cpufreq_generic_suspend,
>>   };
>>
>> +static inline int disable_freq_if_available(struct device *dev,
> 
> The inline isn't needed, esp. on static function, let the compiler
> figure it out.
> 
> Also, "disable if available" should rather be "disable if unavailable" I
> think ?

Here I mean the OPP and I can only disable an available frequency.

> 
>> +                                         unsigned long freq)
>> +{
>> +     struct dev_pm_opp *opp;
>> +     int ret = 0;
>> +
>> +     opp = dev_pm_opp_find_freq_exact(dev, freq, true);
>> +     if (!IS_ERR(opp)) {
>> +             dev_pm_opp_put(opp);
>> +             ret = dev_pm_opp_disable(dev, freq);
>> +     }
>> +
>> +     return ret;
>> +}
>> +
>>   #define OCOTP_CFG3                  0x440
>>   #define OCOTP_CFG3_SPEED_SHIFT              16
>>   #define OCOTP_CFG3_SPEED_1P2GHZ             0x3
>> @@ -254,16 +269,16 @@ static int imx6q_opp_check_speed_grading(struct device *dev)
>>       val &= 0x3;
>>
>>       if (val < OCOTP_CFG3_SPEED_996MHZ)
>> -             if (dev_pm_opp_disable(dev, 996000000))
>> +             if (disable_freq_if_available(dev, 996000000))
>>                       dev_warn(dev, "failed to disable 996MHz OPP\n");
>>
>>       if (of_machine_is_compatible("fsl,imx6q") ||
>>           of_machine_is_compatible("fsl,imx6qp")) {
> 
> Can we introduce a function like:
> 
> void imx_disable_freq_if_unavailable(struct device *dev, u32 freq_mhz,
> u32 val, u32 mask)
> {
>     if (val == mask)
>       return;
>     if (!disable_freq_if_available(dev, freq_mhz * 1000000))
>       return;
>     dev_warn(dev, "failed to disable %dMHz OPP\n", mhz);
> }
> 
> And then just call it multiple times in here, to reduce duplication ?
> 
>>               if (val != OCOTP_CFG3_SPEED_852MHZ)
>> -                     if (dev_pm_opp_disable(dev, 852000000))
>> +                     if (disable_freq_if_available(dev, 852000000))
>>                               dev_warn(dev, "failed to disable 852MHz OPP\n");
> 

Yes, using a function to reduce duplications would be good.


Regards
Christoph