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| author | K Prateek Nayak <kprateek.nayak@amd.com> | 2026-07-27 07:20:49 +0000 |
|---|---|---|
| committer | Mario Limonciello <superm1@kernel.org> | 2026-07-27 19:46:50 -0500 |
| commit | 0e850278016ee7207b58f4e38fa5303ea6a751b4 (patch) | |
| tree | 33369b9587d41317d9c6891f39a3b67ae9f9cc29 | |
| parent | 5c3ecf36d2918facff40548ee6ae28eef0865266 (diff) | |
| download | linux-next-0e850278016ee7207b58f4e38fa5303ea6a751b4.tar.gz linux-next-0e850278016ee7207b58f4e38fa5303ea6a751b4.zip | |
cpufreq/amd-pstate: Remove the defensive check for bios_min_perf
Initialization of bios_min_perf (BIOS Requested CPU Min Freq.) only
succeeds when the driver init finds the CPPC_REQ MSRs to have all 0s
except for MIN_PERF bits.
A kexec puts the driver through the suspend path which, although resets
the min_perf back to bios_min_perf, keeps the rest of the CPPR_REQ
intact with the last value at the time of suspend.
The defensive check for bios_min_perf exists to prevent the min perf
from last CPPC_REQ being incorrectly considered as bios_min_perf when
a kexec switches from an older kernel running the version of driver
which is not aware of bios_min_perf to a newer one.
This scenario is extremely unlikely and Mario suggested it is better to
simplify the initialization rather than complicating the suspend resume
paths.
Drop the defensive check for bios_min_perf initialization and add a
debug message to dump the BIOS Requested Min Freq. to console leaving
enough breadcrumbs for debug if a situation so arises.
Suggested-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://lore.kernel.org/r/20260727072056.1248-3-kprateek.nayak@amd.com
Signed-off-by: Mario Limonciello <superm1@kernel.org>
| -rw-r--r-- | drivers/cpufreq/amd-pstate.c | 19 |
1 files changed, 8 insertions, 11 deletions
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c index 25a179b89a74..4c608dad1b0b 100644 --- a/drivers/cpufreq/amd-pstate.c +++ b/drivers/cpufreq/amd-pstate.c @@ -462,7 +462,6 @@ static int msr_init_perf(struct amd_cpudata *cpudata) { union perf_cached perf = READ_ONCE(cpudata->perf); u64 cap1, numerator, cppc_req; - u8 min_perf; int ret = rdmsrq_safe_on_cpu(cpudata->cpu, MSR_AMD_CPPC_CAP1, &cap1); @@ -478,16 +477,6 @@ static int msr_init_perf(struct amd_cpudata *cpudata) return ret; WRITE_ONCE(cpudata->cppc_req_cached, cppc_req); - min_perf = FIELD_GET(AMD_CPPC_MIN_PERF_MASK, cppc_req); - - /* - * Clear out the min_perf part to check if the rest of the MSR is 0, if yes, this is an - * indication that the min_perf value is the one specified through the BIOS option - */ - cppc_req &= ~(AMD_CPPC_MIN_PERF_MASK); - - if (!cppc_req) - perf.bios_min_perf = min_perf; perf.highest_perf = numerator; perf.max_limit_perf = numerator; @@ -495,6 +484,7 @@ static int msr_init_perf(struct amd_cpudata *cpudata) perf.nominal_perf = FIELD_GET(AMD_CPPC_NOMINAL_PERF_MASK, cap1); perf.lowest_nonlinear_perf = FIELD_GET(AMD_CPPC_LOWNONLIN_PERF_MASK, cap1); perf.lowest_perf = FIELD_GET(AMD_CPPC_LOWEST_PERF_MASK, cap1); + perf.bios_min_perf = FIELD_GET(AMD_CPPC_MIN_PERF_MASK, cppc_req); WRITE_ONCE(cpudata->perf, perf); WRITE_ONCE(cpudata->prefcore_ranking, FIELD_GET(AMD_CPPC_HIGHEST_PERF_MASK, cap1)); WRITE_ONCE(cpudata->floor_perf_cnt, FIELD_GET(AMD_CPPC_FLOOR_PERF_CNT_MASK, cap1)); @@ -1044,6 +1034,13 @@ static int amd_pstate_init_freq(struct amd_cpudata *cpudata) return -EINVAL; } + if (perf.bios_min_perf) { + u32 bios_min_freq = perf_to_freq(perf, cpudata->nominal_freq, perf.bios_min_perf); + + pr_debug("Found Requested CPU Min Frequency of %uKHz on CPU%d\n", + bios_min_freq, cpudata->cpu); + } + return 0; } |