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

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 8ba5259e3d288bd85a6e6e659c1375cff3a73652..3644af1a8e564270eca310e81fe5ee8246a0fbf4 100644 (file)
--- 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);
                }
        }