As per ACPI 6.x s8.4.6.1.4 (CPPC Enable register): "If supported by the platform, OSPM writes a one to this register to enable CPPC on this processor. If not implemented, OSPM assumes the platform always has CPPC enabled." The driver never writes this register. Call cppc_set_enable() at the start of cppc_cpufreq_cpu_init(). Errors are logged but not fatal, as the register is optional. Fixes: 5477fb3bd1e8 ("ACPI / CPPC: Add a CPUFreq driver for use with CPPC") Cc: stable@vger.kernel.org # v6.16+ Signed-off-by: Sumit Gupta --- Sending this separately from the autonomous mode boot parameter series where it was patch 1/2, as it is an independent bug fix. v5 of the series: https://lore.kernel.org/lkml/20260623080652.3353386-1-sumitg@nvidia.com/ drivers/cpufreq/cppc_cpufreq.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c index 957fa7775260..b8f4399b6e0b 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -679,6 +679,14 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy) caps = &cpu_data->perf_caps; policy->driver_data = cpu_data; + /* + * Enable CPPC. The Enable register is optional - some platforms + * may not support it. + */ + ret = cppc_set_enable(cpu, true); + if (ret && ret != -EOPNOTSUPP) + pr_warn("Failed to enable CPPC for CPU%u (%d)\n", cpu, ret); + /* * Set min to lowest nonlinear perf to avoid any efficiency penalty (see * Section 8.4.7.1.1.5 of ACPI 6.1 spec) -- 2.34.1