linux-kernel - Re: [PATCH] cpufreq: amd_freq_sensitivity: Fix sensitivity clamping in amd_powersave_bias

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Message-ID: <20251202190904.27c9bc06@pumpkin>
Date: Tue, 2 Dec 2025 19:09:04 +0000
From: David Laight <david.laight.linux@...il.com>
To: Thorsten Blum <thorsten.blum@...ux.dev>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Viresh Kumar
 <viresh.kumar@...aro.org>, Thomas Renninger <trenn@...e.de>, Borislav
 Petkov <bp@...e.de>, Jacob Shin <jacob.shin@....com>,
 stable@...r.kernel.org, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: amd_freq_sensitivity: Fix sensitivity clamping
 in amd_powersave_bias_target

On Tue,  2 Dec 2025 13:44:28 +0100
Thorsten Blum <thorsten.blum@...ux.dev> wrote:

> The local variable 'sensitivity' was never clamped to 0 or
> POWERSAVE_BIAS_MAX because the return value of clamp() was not used. Fix
> this by assigning the clamped value back to 'sensitivity'.

This actually makes no difference
(assuming od_tuners->powersave_bias <= POWERSAVE_BIAS_MAX).
The only use of 'sensitivity' is the test at the end of the diff.

So I think you could just delete the line.

	David

> 
> Cc: stable@...r.kernel.org
> Fixes: 9c5320c8ea8b ("cpufreq: AMD "frequency sensitivity feedback" powersave bias for ondemand governor")
> Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
> ---
>  drivers/cpufreq/amd_freq_sensitivity.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/amd_freq_sensitivity.c b/drivers/cpufreq/amd_freq_sensitivity.c
> index 13fed4b9e02b..713ccf24c97d 100644
> --- a/drivers/cpufreq/amd_freq_sensitivity.c
> +++ b/drivers/cpufreq/amd_freq_sensitivity.c
> @@ -76,7 +76,7 @@ static unsigned int amd_powersave_bias_target(struct cpufreq_policy *policy,
>  	sensitivity = POWERSAVE_BIAS_MAX -
>  		(POWERSAVE_BIAS_MAX * (d_reference - d_actual) / d_reference);
>  
> -	clamp(sensitivity, 0, POWERSAVE_BIAS_MAX);
> +	sensitivity = clamp(sensitivity, 0, POWERSAVE_BIAS_MAX);
>  
>  	/* this workload is not CPU bound, so choose a lower freq */
>  	if (sensitivity < od_tuners->powersave_bias) {