drm/panthor: Make sure caches are flushed/invalidated when an AS is recycled

When we re-assign a slot to a different VM, we need to make sure the
old VM caches are flushed before doing the switch. Specialize
panthor_mmu_as_disable() so we can skip the slot programmation while
still getting the cache flushing, and call this helper from
panthor_vm_active() when an idle slot is recycled.

v2:
- Collect R-bs

Fixes: 6e2d3b3e8589 ("drm/panthor: Add support for atomic page table updates")
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patch.msgid.link/20251203121750.404340-3-boris.brezillon@collabora.com

1 files changed, 20 insertions, 6 deletions

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 8ba5259e3d28..3644af1a8e56 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -585,7 +585,8 @@ static int panthor_mmu_as_enable(struct panthor_device *ptdev, u32 as_nr,
 	return as_send_cmd_and_wait(ptdev, as_nr, AS_COMMAND_UPDATE);
 }
 
-static int panthor_mmu_as_disable(struct panthor_device *ptdev, u32 as_nr)
+static int panthor_mmu_as_disable(struct panthor_device *ptdev, u32 as_nr,
+				  bool recycle_slot)
 {
 	int ret;
 
@@ -595,6 +596,12 @@ static int panthor_mmu_as_disable(struct panthor_device *ptdev, u32 as_nr)
 	if (ret)
 		return ret;
 
+	/* If the slot is going to be used immediately, don't bother changing
+	 * the config.
+	 */
+	if (recycle_slot)
+		return 0;
+
 	gpu_write64(ptdev, AS_TRANSTAB(as_nr), 0);
 	gpu_write64(ptdev, AS_MEMATTR(as_nr), 0);
 	gpu_write64(ptdev, AS_TRANSCFG(as_nr), AS_TRANSCFG_ADRMODE_UNMAPPED);
@@ -714,6 +721,11 @@ int panthor_vm_active(struct panthor_vm *vm)
 
 		drm_WARN_ON(&ptdev->base, refcount_read(&lru_vm->as.active_cnt));
 		as = lru_vm->as.id;
+
+		ret = panthor_mmu_as_disable(ptdev, as, true);
+		if (ret)
+			goto out_unlock;
+
 		panthor_vm_release_as_locked(lru_vm);
 	}
 
@@ -853,7 +865,7 @@ static void panthor_vm_declare_unusable(struct panthor_vm *vm)
 	vm->unusable = true;
 	mutex_lock(&ptdev->mmu->as.slots_lock);
 	if (vm->as.id >= 0 && drm_dev_enter(&ptdev->base, &cookie)) {
-		panthor_mmu_as_disable(ptdev, vm->as.id);
+		panthor_mmu_as_disable(ptdev, vm->as.id, false);
 		drm_dev_exit(cookie);
 	}
 	mutex_unlock(&ptdev->mmu->as.slots_lock);
@@ -1780,7 +1792,7 @@ static void panthor_mmu_irq_handler(struct panthor_device *ptdev, u32 status)
 			ptdev->mmu->as.slots[as].vm->unhandled_fault = true;
 
 		/* Disable the MMU to kill jobs on this AS. */
-		panthor_mmu_as_disable(ptdev, as);
+		panthor_mmu_as_disable(ptdev, as, false);
 		mutex_unlock(&ptdev->mmu->as.slots_lock);
 
 		status &= ~mask;
@@ -1809,7 +1821,8 @@ void panthor_mmu_suspend(struct panthor_device *ptdev)
 		struct panthor_vm *vm = ptdev->mmu->as.slots[i].vm;
 
 		if (vm) {
-			drm_WARN_ON(&ptdev->base, panthor_mmu_as_disable(ptdev, i));
+			drm_WARN_ON(&ptdev->base,
+				    panthor_mmu_as_disable(ptdev, i, false));
 			panthor_vm_release_as_locked(vm);
 		}
 	}
@@ -1930,7 +1943,7 @@ static void panthor_vm_free(struct drm_gpuvm *gpuvm)
 		int cookie;
 
 		if (drm_dev_enter(&ptdev->base, &cookie)) {
-			panthor_mmu_as_disable(ptdev, vm->as.id);
+			panthor_mmu_as_disable(ptdev, vm->as.id, false);
 			drm_dev_exit(cookie);
 		}
 
@@ -2790,7 +2803,8 @@ void panthor_mmu_unplug(struct panthor_device *ptdev)
 		struct panthor_vm *vm = ptdev->mmu->as.slots[i].vm;
 
 		if (vm) {
-			drm_WARN_ON(&ptdev->base, panthor_mmu_as_disable(ptdev, i));
+			drm_WARN_ON(&ptdev->base,
+				    panthor_mmu_as_disable(ptdev, i, false));
 			panthor_vm_release_as_locked(vm);
 		}
 	}