[PATCH] drm/panthor: ignore CS IRQs for uninitialized slots

[Osama Abdelkader <osama.abdelkader@gmail.com>]

CS interrupts are reported through firmware-provided bits in the CSG
interface. sched_process_csg_irq_locked() iterates over those bits and
passes each CS ID to cs_slot_process_irq_locked().

panthor_fw_get_cs_iface() only bounds the CS ID against MAX_CS_PER_CSG,
while the firmware can expose fewer CS slots. If an IRQ bit is reported
for a slot beyond sched->cs_slot_count, the driver can fetch a
zero-initialized interface entry and dereference cs_iface->input.

Ignore IRQs for slots that were not exposed by the firmware. The CSG IRQ
acknowledgment is already updated from cs_irq_req before processing the
individual CS IRQs, so ignored bits are still acknowledged.

Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block")
Cc: stable@vger.kernel.org
Signed-off-by: Osama Abdelkader <osama.abdelkader@gmail.com>
---
 drivers/gpu/drm/panthor/panthor_sched.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index 64749750e6ee..1e230936e99c 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -1705,6 +1705,9 @@ static bool cs_slot_process_irq_locked(struct panthor_device *ptdev,
 
 	lockdep_assert_held(&ptdev->scheduler->lock);
 
+	if (cs_id >= ptdev->scheduler->cs_slot_count)
+		return false;
+
 	cs_iface = panthor_fw_get_cs_iface(ptdev, csg_id, cs_id);
 	req = cs_iface->input->req;
 	ack = cs_iface->output->ack;
-- 
2.43.0