5.0-stable review patch. If anyone has any objections, please let me know.
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From: Srinivas Pandruvada srinivas.pandruvada@linux.intel.com
commit 92a3e426ec06e72b1c363179c79d30712447ff76 upstream.
The ACPI specification states that if the "Guaranteed Performance Register" is not implemented, the OSPM assumes guaranteed performance to always be equal to nominal performance.
So for invalid or unimplemented guaranteed performance register, use nominal performance as guaranteed performance.
This change will fall back to nominal_perf when guranteed_perf is invalid. If nominal_perf is also invalid or not present, fall back to the existing implementation, which is to read from HWP Capabilities MSR.
Fixes: 86d333a8cc7f ("cpufreq: intel_pstate: Add base_frequency attribute") Suggested-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Srinivas Pandruvada srinivas.pandruvada@linux.intel.com Cc: 4.20+ stable@vger.kernel.org # 4.20+ Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/cpufreq/intel_pstate.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
--- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -383,7 +383,10 @@ static int intel_pstate_get_cppc_gurante if (ret) return ret;
- return cppc_perf.guaranteed_perf; + if (cppc_perf.guaranteed_perf) + return cppc_perf.guaranteed_perf; + + return cppc_perf.nominal_perf; }
#else /* CONFIG_ACPI_CPPC_LIB */