[PATCH 5.10.y] cpufreq: intel_pstate: Sync policy->cur during CPU offline

[Sasha Levin <sashal@kernel.org>]

From: Fushuai Wang <wangfushuai@baidu.com>

[ Upstream commit bcbdaa1086c25a8a5d48e04e1b82fdfb0682b681 ]

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@vger.kernel.org # 3.15+
Suggested-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Fushuai Wang <wangfushuai@baidu.com>
[ rjw: Subject refinement ]
Link: https://patch.msgid.link/20260520032119.30615-1-fushuai.wang@linux.dev
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
[ replaced `cpu->pstate.min_freq` with `cpu->pstate.min_pstate * cpu->pstate.scaling` since 5.10 lacks the min_freq field ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 e0a7d580d48729..8dc11d5fed17b6 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2355,10 +2355,12 @@ static int intel_pstate_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_pstate * cpu->pstate.scaling;
+	}
 
 	intel_pstate_exit_perf_limits(policy);
 
-- 
2.53.0