linux-kernel - Re: [PATCH 2/3] arch_topology: obtain cpu capacity using information from CPPC

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Date:   Tue, 18 May 2021 14:12:14 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Ionela Voinescu <ionela.voinescu@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/3] arch_topology: obtain cpu capacity using information from CPPC

On 14/05/21 10:53, Ionela Voinescu wrote:
> +#ifdef CONFIG_ACPI_CPPC_LIB
> +#include <acpi/cppc_acpi.h>
> +
> +void init_cpu_capacity_cppc(void)
> +{
> +	struct cppc_perf_caps perf_caps;
> +	int cpu;
> +
> +	if (likely(acpi_disabled || !acpi_cpc_valid()))
> +		return;
> +
> +	raw_capacity = kcalloc(num_possible_cpus(), sizeof(*raw_capacity),
> +			       GFP_KERNEL);

Per the below loop, the memory shouldn't need to be cleared.

> +	if (!raw_capacity)
> +		return;
> +
> +	for_each_possible_cpu(cpu) {
> +		if (!cppc_get_perf_caps(cpu, &perf_caps)) {
> +			raw_capacity[cpu] = perf_caps.highest_perf;
> +			pr_debug("%s: CPU%d cpu_capacity=%u (raw).\n",
> +				 __func__, cpu, raw_capacity[cpu]);
> +		} else {
> +			pr_err("%s: CPU%d missing highest performance.\n",
> +				 __func__, cpu);
> +			pr_err("%s: fallback to 1024 for all CPUs\n",
> +				 __func__);
> +			goto exit;
> +		}
> +	}
> +
> +	topology_normalize_cpu_scale();
> +	schedule_work(&update_topology_flags_work);
> +	pr_debug("%s: cpu_capacity initialization done\n", __func__);
> +
> +exit:
> +	free_raw_capacity();
> +}
> +#endif