[PATCH] perf: arm_pmu_acpi: Get rid of the edge-triggered interrupt oddity

[PATCH] perf: arm_pmu_acpi: Get rid of the edge-triggered interrupt oddity

[Marc Zyngier]

The ACPI spec bizarrely indicates that the PMU interrupt can be
edge-triggered, which contradicts the very basics of the PMU
architecture (SW is required to clear the interrupt condition for
the level to drop).

Remove the code parsing this flag and always flag the interrupt
as level triggered, no matter what firmware says.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 drivers/perf/arm_pmu_acpi.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c
index e80f76d95e68b..ca6bf8f86cfe9 100644
--- a/drivers/perf/arm_pmu_acpi.c
+++ b/drivers/perf/arm_pmu_acpi.c
@@ -22,7 +22,7 @@ static DEFINE_PER_CPU(int, pmu_irqs);
 static int arm_pmu_acpi_register_irq(int cpu)
 {
 	struct acpi_madt_generic_interrupt *gicc;
-	int gsi, trigger;
+	int gsi;
 
 	gicc = acpi_cpu_get_madt_gicc(cpu);
 
@@ -38,11 +38,6 @@ static int arm_pmu_acpi_register_irq(int cpu)
 	if (!gsi)
 		return 0;
 
-	if (gicc->flags & ACPI_MADT_PERFORMANCE_IRQ_MODE)
-		trigger = ACPI_EDGE_SENSITIVE;
-	else
-		trigger = ACPI_LEVEL_SENSITIVE;
-
 	/*
 	 * Helpfully, the MADT GICC doesn't have a polarity flag for the
 	 * "performance interrupt". Luckily, on compliant GICs the polarity is
@@ -53,8 +48,12 @@ static int arm_pmu_acpi_register_irq(int cpu)
 	 * may not match the real polarity, but that should not matter.
 	 *
 	 * Other interrupt controllers are not supported with ACPI.
+	 *
+	 * The spec also indicates that the PMU interrupt can be edge
+	 * triggered, which doesn't make any sense (SW needs to clear the
+	 * interrupt condition for the level to drop). Ignore the silly flag.
 	 */
-	return acpi_register_gsi(NULL, gsi, trigger, ACPI_ACTIVE_HIGH);
+	return acpi_register_gsi(NULL, gsi, ACPI_LEVEL_SENSITIVE, ACPI_ACTIVE_HIGH);
 }
 
 static void arm_pmu_acpi_unregister_irq(int cpu)
-- 
2.47.3

Re: [PATCH] perf: arm_pmu_acpi: Get rid of the edge-triggered interrupt oddity

[Zenghui Yu]

On 2026/7/26 0:26, Marc Zyngier wrote:
> The ACPI spec bizarrely indicates that the PMU interrupt can be
> edge-triggered, which contradicts the very basics of the PMU
> architecture (SW is required to clear the interrupt condition for
> the level to drop).
> 
> Remove the code parsing this flag and always flag the interrupt
> as level triggered, no matter what firmware says.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  drivers/perf/arm_pmu_acpi.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)

Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>

Thanks,
Zenghui