[PATCH 1/3] soc: samsung: exynos-pmu: use target cpu ID in hotplug callbacks

[Alexey Klimov]

The CPU hotplug state callbacks __gs101_cpu_pmu_online() and
__gs101_cpu_pmu_offline() currently partially use smp_processor_id() to
determine the target register offset for the CPU inform hints. This may
be fine for cpuidle flow but broken for cpu hotplug where the target
cpu is passed as an argument and could be different from cpu where
that is executing (e.g. CPU 0 offlining CPU 1), meaning that
smp_processor_id() returns the id of local CPU but hotplug flow
deals with another CPU core undergoing the transition.

This causes the pmu driver to write power down and power on configuration
hints to the wrong hardware registers, messing up the power state of active
cores and failing to configure the target core. Fix this by removing the
cpuhint variable entirely and utilizing the target 'cpu' argument passed
to the callbacks by the hotplug core infrastructure.

Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Closes: https://sashiko.dev/#/patchset/20260513-exynos850-cpuhotplug-v4-0-54fec5f65362@xxxxxxxxxx?part=3
Fixes: 598995027b91 ("soc: samsung: exynos-pmu: enable CPU hotplug support for gs101")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Alexey Klimov <alexey.klimov@xxxxxxxxxx>
---
 drivers/soc/samsung/exynos-pmu.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/soc/samsung/exynos-pmu.c b/drivers/soc/samsung/exynos-pmu.c
index d58376c38179..6e635872247a 100644
--- a/drivers/soc/samsung/exynos-pmu.c
+++ b/drivers/soc/samsung/exynos-pmu.c
@@ -235,11 +235,10 @@ EXPORT_SYMBOL_GPL(exynos_get_pmu_regmap_by_phandle);
 static int __gs101_cpu_pmu_online(unsigned int cpu)
 	__must_hold(&pmu_context->cpupm_lock)
 {
-	unsigned int cpuhint = smp_processor_id();
 	u32 reg, mask;
 
 	/* clear cpu inform hint */
-	regmap_write(pmu_context->pmureg, GS101_CPU_INFORM(cpuhint),
+	regmap_write(pmu_context->pmureg, GS101_CPU_INFORM(cpu),
 		     CPU_INFORM_CLEAR);
 
 	mask = BIT(cpu);
@@ -296,12 +295,10 @@ static int gs101_cpuhp_pmu_online(unsigned int cpu)
 static int __gs101_cpu_pmu_offline(unsigned int cpu)
 	__must_hold(&pmu_context->cpupm_lock)
 {
-	unsigned int cpuhint = smp_processor_id();
 	u32 reg, mask;
 
 	/* set cpu inform hint */
-	regmap_write(pmu_context->pmureg, GS101_CPU_INFORM(cpuhint),
-		     CPU_INFORM_C2);
+	regmap_write(pmu_context->pmureg, GS101_CPU_INFORM(cpu), CPU_INFORM_C2);
 
 	mask = BIT(cpu);
 	regmap_update_bits(pmu_context->pmuintrgen, GS101_GRP2_INTR_BID_ENABLE,

-- 
2.51.0