From 37b6ddba967c601479bea418a7ac6ff16b6232b7 Mon Sep 17 00:00:00 2001
From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Date: Thu, 7 Sep 2023 11:02:07 -0700
Subject: [PATCH] cpufreq: intel_pstate: Revise global turbo disable check
Setting global turbo flag based on CPU 0 P-state limits is problematic
as it limits max P-state request on every CPU on the system just based
on its P-state limits.
There are two cases in which global.turbo_disabled flag is set:
- When the MSR_IA32_MISC_ENABLE_TURBO_DISABLE bit is set to 1
in the MSR MSR_IA32_MISC_ENABLE. This bit can be only changed by
the system BIOS before power up.
- When the max non turbo P-state is same as max turbo P-state for CPU 0.
The second check is not a valid to decide global turbo state based on
the CPU 0. CPU 0 max turbo P-state can be same as max non turbo P-state,
but for other CPUs this may not be true.
There is no guarantee that max P-state limits are same for every CPU. This
is possible that during fusing max P-state for a CPU is constrained. Also
with the Intel Speed Select performance profile, CPU 0 may not be present
in all profiles. In this case the max non turbo and turbo P-state can be
set to the lowest possible P-state by the hardware when switched to
such profile. Since max non turbo and turbo P-state is same,
global.turbo_disabled flag will be set.
Once global.turbo_disabled is set, any scaling max and min frequency
update for any CPU will result in its max P-state constrained to the max
non turbo P-state.
Hence remove the check of max non turbo P-state equal to max turbo P-state
of CPU 0 to set global turbo disabled flag.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw: Subject edit ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/cpufreq/intel_pstate.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index dc50c9fb488df..a534a1f7f1ee7 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -571,13 +571,9 @@ static void intel_pstate_hybrid_hwp_adjust(struct cpudata *cpu)
static inline void update_turbo_state(void)
{
u64 misc_en;
- struct cpudata *cpu;
- cpu = all_cpu_data[0];
rdmsrl(MSR_IA32_MISC_ENABLE, misc_en);
- global.turbo_disabled =
- (misc_en & MSR_IA32_MISC_ENABLE_TURBO_DISABLE ||
- cpu->pstate.max_pstate == cpu->pstate.turbo_pstate);
+ global.turbo_disabled = misc_en & MSR_IA32_MISC_ENABLE_TURBO_DISABLE;
}
static int min_perf_pct_min(void)
--
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