[PATCH v2 6/9] cpufreq: amd_pstate: add AMD pstate EPP support for shared memory type processor

From: Perry Yuan
Date: Sun Oct 09 2022 - 03:11:59 EST


Add Energy Performance Preference support for AMD SOCs which do not
contain a designated MSR for CPPC support. A shared memory interface
is used for CPPC on these SOCs and the ACPI PCC channel is used to
enable EPP and reset the desired performance.

Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
---
drivers/cpufreq/amd-pstate.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 14a275c22aff..4c24fe391a55 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -135,12 +135,25 @@ static inline int pstate_enable(bool enable)

static int cppc_enable(bool enable)
{
+ struct cppc_perf_ctrls perf_ctrls;
int cpu, ret = 0;

for_each_present_cpu(cpu) {
ret = cppc_set_enable(cpu, enable);
if (ret)
return ret;
+ if (epp_enabled) {
+ /* Enable autonomous mode for EPP */
+ ret = cppc_set_auto_epp(cpu, enable);
+ if (ret)
+ return ret;
+
+ /* Set desired perf as zero to allow EPP firmware control */
+ perf_ctrls.desired_perf = 0;
+ ret = cppc_set_perf(cpu, &perf_ctrls);
+ if (ret)
+ return ret;
+ }
}

return ret;
--
2.34.1