[PATCH] [PATCH] amd_pstate: fix erroneous highest_perf value on some CPUs

Lucas Lee Jing Yi
2024-02-18T16:15:07Z

On a Ryzen 7840HS the highest_perf value is 196, not 166 as AMD assumed.
This leads to the advertised max clock speed to only be 4.35ghz instead of 5.14ghz , leading to a large degradation in performance.

Fix the broken assumption and revert back to the old logic for getting highest_perf.

TEST:
Geekbench 6 Before Patch:
Single Core: 2325 (-22%)!
Multi Core: 11335 (-10%)

Geekbench 6 AFTER Patch:
Single Core: 2635
Multi Core: 12487

Signed-off-by: Lucas Lee Jing Yi <lucasleeeeeeeee@gmail.com>
---
drivers/cpufreq/amd-pstate.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 08e112444c27..54df68773620 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -50,7 +50,6 @@

#define AMD_PSTATE_TRANSITION_LATENCY 20000
#define AMD_PSTATE_TRANSITION_DELAY 1000
-#define AMD_PSTATE_PREFCORE_THRESHOLD 166

/*
* TODO: We need more time to fine tune processors with shared memory solution
@@ -299,15 +298,12 @@ static int pstate_init_perf(struct amd_cpudata *cpudata)
&cap1);
if (ret)
return ret;
-
- /* For platforms that do not support the preferred core feature, the
- * highest_pef may be configured with 166 or 255, to avoid max frequency
- * calculated wrongly. we take the AMD_CPPC_HIGHEST_PERF(cap1) value as
- * the default max perf.
+
+ /* Some CPUs have different highest_perf from others, it is safer
+ * to read it than to assume some erroneous value, leading to performance issues.
*/
- if (cpudata->hw_prefcore)
- highest_perf = AMD_PSTATE_PREFCORE_THRESHOLD;
- else
+ highest_perf = amd_get_highest_perf();
+ if(highest_perf > AMD_CPPC_HIGHEST_PERF(cap1))
highest_perf = AMD_CPPC_HIGHEST_PERF(cap1);

WRITE_ONCE(cpudata->highest_perf, highest_perf);
@@ -329,9 +325,11 @@ static int cppc_init_perf(struct amd_cpudata *cpudata)
if (ret)
return ret;

- if (cpudata->hw_prefcore)
- highest_perf = AMD_PSTATE_PREFCORE_THRESHOLD;
- else
+ /* Some CPUs have different highest_perf from others, it is safer
+ * to read it than to assume some erroneous value, leading to performance issues.
+ */
+ highest_perf = amd_get_highest_perf();
+ if(highest_perf > cppc_perf.highest_perf)
highest_perf = cppc_perf.highest_perf;

WRITE_ONCE(cpudata->highest_perf, highest_perf);
--
2.43.2