Commit edef1ef1 authored Mar 25, 2019 by Srinivas Pandruvada Committed by Rafael J. Wysocki Mar 25, 2019

ACPI / CPPC: Fix guaranteed performance handling



As per the ACPI specification, "Guaranteed Performance Register" is
a "Buffer" field and it cannot be "Integer", so treat the "Integer"
type for "Guaranteed Performance Register" field as invalid and
ignore its value in that case.

Also save one cpc_read() call when "Guaranteed Performance Register"
is not present, which means a register defined as:
"Register(SystemMemory, 0, 0, 0, 0)".

Fixes: 29523f09 ("ACPI / CPPC: Add support for guaranteed performance")
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>

parent 8c2ffd91

drivers/acpi/cppc_acpi.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -1150,8 +1150,13 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
		cpc_read(cpunum, nominal_reg, &nom);
		perf_caps->nominal_perf = nom;

		if (guaranteed_reg->type != ACPI_TYPE_BUFFER \|\|
		IS_NULL_REG(&guaranteed_reg->cpc_entry.reg)) {
		perf_caps->guaranteed_perf = 0;
		} else {
		cpc_read(cpunum, guaranteed_reg, &guaranteed);
		perf_caps->guaranteed_perf = guaranteed;
		}

		cpc_read(cpunum, lowest_non_linear_reg, &min_nonlinear);
		perf_caps->lowest_nonlinear_perf = min_nonlinear;

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