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

[Rafael J. Wysocki]

On 5/6/2020 7:42 PM, Sergey.Semin@xxxxxxxxxxxxxxxxxxxx wrote:
> From: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
>
> Recent commit e61a41256edf ("cpufreq: dev_pm_qos_update_request() can
> return 1 on success") fixed a problem when active policies traverse
> was falsely stopped due to invalidly treating the non-zero return value
> from freq_qos_update_request() method as an error. Yes, that function
> can return positive values if the requested update actually took place.
> The current problem is that the returned value is then passed to the
> return cell of the cpufreq_boost_set_sw() (set_boost callback) method.
> This value is then also analyzed for being non-zero, which is also
> treated as having an error. As a result during the boost activation
> we'll get an error returned while having the QOS frequency update
> successfully performed. Fix this by returning a negative value from the
> cpufreq_boost_set_sw() if actual error was encountered and zero
> otherwise treating any positive values as the successful operations
> completion.
>
> Fixes: 18c49926c4bf ("cpufreq: Add QoS requests for userspace constraints")
> Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
> Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> Cc: Alexey Malahov <Alexey.Malahov@xxxxxxxxxxxxxxxxxxxx>
> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> Cc: Paul Burton <paulburton@xxxxxxxxxx>
> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> Cc: linux-mips@xxxxxxxxxxxxxxx
> Cc: devicetree@xxxxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>   drivers/cpufreq/cpufreq.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 045f9fe157ce..5870cdca88cf 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -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.

Thanks!