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

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On 2/21/2024 11:19, Lucas Lee Jing Yi wrote:
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


Yes; the max boost for your system should be 5.1GHz according to the specification [1].

Would you please open a kernel Bugzilla and attach an acpidump and dmesg for your system? I believe we need to better understand your system's situation before deciding on how to correctly approach it.

[1] https://www.amd.com/en/product/13041

Signed-off-by: Lucas Lee Jing Yi <lucasleeeeeeeee@xxxxxxxxx>
---
  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);





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