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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: 29523f0953 ("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>
hifive-unleashed-5.1
Srinivas Pandruvada 2019-03-25 09:04:39 -07:00 committed by Rafael J. Wysocki
parent 8c2ffd9174
commit edef1ef134
1 changed files with 7 additions and 2 deletions
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9
drivers/acpi/cppc_acpi.c
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@ -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;
cpc_read(cpunum, guaranteed_reg, &guaranteed);
perf_caps->guaranteed_perf = guaranteed;
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;