linux-kernel - Re: [PATCH 2/2] cpufreq: CPPC: Fix error handling in cppc_scale_freq

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Message-ID: <20250730063930.cercfcpjwnfbnskj@vireshk-i7>
Date: Wed, 30 Jul 2025 12:09:30 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Bowen Yu <yubowen8@...wei.com>
Cc: rafael@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxarm@...wei.com,
	jonathan.cameron@...wei.com, zhanjie9@...ilicon.com,
	lihuisong@...wei.com, zhenglifeng1@...wei.com,
	Prashant Malani <pmalani@...gle.com>,
	Beata Michalska <beata.michalska@....com>,
	Ionela Voinescu <ionela.voinescu@....com>
Subject: Re: [PATCH 2/2] cpufreq: CPPC: Fix error handling in
 cppc_scale_freq_workfn()

+ Prashant/Beata/Ionela

On 30-07-25, 11:23, Bowen Yu wrote:
> From: Jie Zhan <zhanjie9@...ilicon.com>
> 
> Perf counters could be 0 if the cpu is in a low-power idle state. Just try
> it again next time and update the frequency scale when the cpu is active
> and perf counters successfully return.
> 
> Also, remove the FIE source on an actual failure.
> 
> Signed-off-by: Jie Zhan <zhanjie9@...ilicon.com>
> ---
>  drivers/cpufreq/cppc_cpufreq.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> index 904006027df2..e95844d3d366 100644
> --- a/drivers/cpufreq/cppc_cpufreq.c
> +++ b/drivers/cpufreq/cppc_cpufreq.c
> @@ -78,12 +78,23 @@ static void cppc_scale_freq_workfn(struct kthread_work *work)
>  	struct cppc_cpudata *cpu_data;
>  	unsigned long local_freq_scale;
>  	u64 perf;
> +	int ret;
>  
>  	cppc_fi = container_of(work, struct cppc_freq_invariance, work);
>  	cpu_data = cppc_fi->cpu_data;
>  
> -	if (cppc_get_perf_ctrs(cppc_fi->cpu, &fb_ctrs)) {
> +	ret = cppc_get_perf_ctrs(cppc_fi->cpu, &fb_ctrs);
> +	/*
> +	 * Perf counters could be 0 if the cpu is in a low-power idle state.
> +	 * Just try it again next time.
> +	 */
> +	if (ret == -EFAULT)
> +		return;
> +
> +	if (ret) {
>  		pr_warn("%s: failed to read perf counters\n", __func__);
> +		topology_clear_scale_freq_source(SCALE_FREQ_SOURCE_CPPC,
> +						 cpu_data->shared_cpu_map);
>  		return;
>  	}
>  
> -- 
> 2.33.0

-- 
viresh