[RFC PATCH 6.1.y 1/1] cpufreq: amd-pstate: Enable CPU boost in passive and guided modes

Nabil S. Alramli
2024-10-25T02:06:32Z

The CPU frequency cannot be boosted when using the amd_pstate driver in
passive or guided mode. This is fixed here.

The CPU frequency is dependent on a setting called highest_perf which is
the multiplier used to compute it. The highest_perf value comes from
cppc_init_perf when the driver is built-in and from pstate_init_perf when
it is a loaded module. Both of these calls have the following condition:

highest_perf = amd_get_highest_perf();
if (highest_perf > __cppc_highest_perf_)
highest_perf = __cppc_highest_perf;

Where again __cppc_highest_perf is either the return from
cppc_get_perf_caps in the built-in case or AMD_CPPC_HIGHEST_PERF in the
module case. Both of these functions actually return the nominal value,
Whereas the call to amd_get_highest_perf returns the correct boost value,
so the condition tests true and highest_perf always ends up being the
nominal value, therefore never having the ability to boost CPU frequency.

Since amd_get_highest_perf already returns the boost value we should just
eliminate this check.

Signed-off-by: Nabil S. Alramli <dev@nalramli.com>
Fixes: bedadcfb011f ("cpufreq: amd-pstate: Fix initial highest_perf value")
See-also: 1ec40a175a48 ("cpufreq: amd-pstate: Enable amd-pstate preferred core support")
Cc: Perry.Yuan@amd.com
Cc: li.meng@amd.com
Cc: stable@vger.kernel.org # 6.1 - v6.6.50
---
drivers/cpufreq/amd-pstate.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 90dcf26f0973..c66086ae624a 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -102,9 +102,7 @@ static int pstate_init_perf(struct amd_cpudata *cpudata)
*
* CPPC entry doesn't indicate the highest performance in some ASICs.
*/
- highest_perf = amd_get_highest_perf();
- if (highest_perf > AMD_CPPC_HIGHEST_PERF(cap1))
- highest_perf = AMD_CPPC_HIGHEST_PERF(cap1);
+ highest_perf = max(amd_get_highest_perf(), AMD_CPPC_HIGHEST_PERF(cap1));

WRITE_ONCE(cpudata->highest_perf, highest_perf);

@@ -124,9 +122,7 @@ static int cppc_init_perf(struct amd_cpudata *cpudata)
if (ret)
return ret;

- highest_perf = amd_get_highest_perf();
- if (highest_perf > cppc_perf.highest_perf)
- highest_perf = cppc_perf.highest_perf;
+ highest_perf = max(amd_get_highest_perf(), cppc_perf.highest_perf);

WRITE_ONCE(cpudata->highest_perf, highest_perf);

--
2.35.1