[PATCH v2] cpufreq: intel_pstate: Sync policy->cur when setting min pstate during CPU offline

[Fushuai Wang]

From: Fushuai Wang <wangfushuai@xxxxxxxxx>

When a CPU goes offline with HWP disabled, intel_pstate_set_min_pstate()
sets the MSR_IA32_PERF_CTL to minimum frequency to prevent SMT siblings
from being restricted. However, the policy->cur value was not updated,
leaving it at the previous value.

When the CPU comes back online, governor->limits() checks if target_freq
equals policy->cur and skips the frequency adjustment if they match. Since
policy->cur still holds the previous value, the governor does not call
cpufreq_driver->target to update MSR_IA32_PERF_CTL.

Fix this by synchronizing policy->cur with the hardware state when setting
minimum pstate during CPU offline.

Fixes: bb18008f8086 ("intel_pstate: Set core to min P state during core offline")
Cc: stable@xxxxxxxxxxxxxxx # 3.15+
Suggested-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
Signed-off-by: Fushuai Wang <wangfushuai@xxxxxxxxx>
---
 drivers/cpufreq/intel_pstate.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 1292da53e5fc..11db1c887c80 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2984,10 +2984,12 @@ static int intel_cpufreq_cpu_offline(struct cpufreq_policy *policy)
 	 * from getting to lower performance levels, so force the minimum
 	 * performance on CPU offline to prevent that from happening.
 	 */
-	if (hwp_active)
+	if (hwp_active) {
 		intel_pstate_hwp_offline(cpu);
-	else
+	} else {
 		intel_pstate_set_min_pstate(cpu);
+		policy->cur = cpu->pstate.min_freq;
+	}
 
 	intel_pstate_exit_perf_limits(policy);
 
-- 
2.36.1