As per ACPI specification "Guaranteed Performance Register" is a "Buffer" field. It can't be "Integer" field. So treat "Integer" type as invalid and ignore "Guaranteed Performance Register". Also save one cpc_read() call, when "Guaranteed Performance Register" is not present, which means register defined as: "Register(SystemMemory, 0, 0, 0, 0)".
Fixes: 29523f095397 ("ACPI / CPPC: Add support for guaranteed performance") Signed-off-by: Srinivas Pandruvada srinivas.pandruvada@linux.intel.com Cc: 4.20+ stable@vger.kernel.org # 4.20+ --- drivers/acpi/cppc_acpi.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 1b207fca1420..3f6c290e06af 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -1150,8 +1150,14 @@ 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_INTEGER || + (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;