[PATCH 2/4] panthor: save panthor_file in panthor_group

[Chia-I Wu <olvaffe@gmail.com>]

We would like to access panthor_file from panthor_group on gpu errors.
Because panthour_group can outlive drm_file, add refcount to
panthor_file to ensure its lifetime.

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
---
 drivers/gpu/drm/panthor/panthor_device.h | 16 ++++++++++++++++
 drivers/gpu/drm/panthor/panthor_drv.c    | 15 ++++++++++++++-
 drivers/gpu/drm/panthor/panthor_mmu.c    |  1 +
 drivers/gpu/drm/panthor/panthor_sched.c  |  6 ++++++
 4 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
index 4fc7cf2aeed57..75ae6fd3a5128 100644
--- a/drivers/gpu/drm/panthor/panthor_device.h
+++ b/drivers/gpu/drm/panthor/panthor_device.h
@@ -256,8 +256,24 @@ struct panthor_file {
 
 	/** @stats: cycle and timestamp measures for job execution. */
 	struct panthor_gpu_usage stats;
+
+	/** @refcount: ref count of this file */
+	struct kref refcount;
 };
 
+static inline struct panthor_file *panthor_file_get(struct panthor_file *pfile)
+{
+	kref_get(&pfile->refcount);
+	return pfile;
+}
+
+void panthor_file_release(struct kref *kref);
+
+static inline void panthor_file_put(struct panthor_file *pfile)
+{
+	kref_put(&pfile->refcount, panthor_file_release);
+}
+
 int panthor_device_init(struct panthor_device *ptdev);
 void panthor_device_unplug(struct panthor_device *ptdev);
 
diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
index 775a66c394544..aea9609684b77 100644
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -1393,6 +1393,16 @@ static int panthor_ioctl_set_user_mmio_offset(struct drm_device *ddev,
 	return 0;
 }
 
+void panthor_file_release(struct kref *kref)
+{
+	struct panthor_file *pfile =
+		container_of(kref, struct panthor_file, refcount);
+
+	WARN_ON(pfile->vms || pfile->groups);
+
+	kfree(pfile);
+}
+
 static int
 panthor_open(struct drm_device *ddev, struct drm_file *file)
 {
@@ -1426,6 +1436,8 @@ panthor_open(struct drm_device *ddev, struct drm_file *file)
 	if (ret)
 		goto err_destroy_vm_pool;
 
+	kref_init(&pfile->refcount);
+
 	file->driver_priv = pfile;
 	return 0;
 
@@ -1442,10 +1454,11 @@ panthor_postclose(struct drm_device *ddev, struct drm_file *file)
 {
 	struct panthor_file *pfile = file->driver_priv;
 
+	/* destroy vm and group handles now to avoid circular references */
 	panthor_group_pool_destroy(pfile);
 	panthor_vm_pool_destroy(pfile);
 
-	kfree(pfile);
+	panthor_file_put(pfile);
 }
 
 static const struct drm_ioctl_desc panthor_drm_driver_ioctls[] = {
diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index b39ea6acc6a96..ccbcfe11420ac 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -1604,6 +1604,7 @@ void panthor_vm_pool_destroy(struct panthor_file *pfile)
 
 	xa_destroy(&pfile->vms->xa);
 	kfree(pfile->vms);
+	pfile->vms = NULL;
 }
 
 /**
diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index a2248f692a030..485072904cd7d 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -535,6 +535,9 @@ struct panthor_group {
 	/** @ptdev: Device. */
 	struct panthor_device *ptdev;
 
+	/** @pfile: File this group is created from. */
+	struct panthor_file *pfile;
+
 	/** @vm: VM bound to the group. */
 	struct panthor_vm *vm;
 
@@ -919,6 +922,7 @@ static void group_release_work(struct work_struct *work)
 	panthor_kernel_bo_destroy(group->syncobjs);
 
 	panthor_vm_put(group->vm);
+	panthor_file_put(group->pfile);
 	kfree(group);
 }
 
@@ -3467,6 +3471,8 @@ int panthor_group_create(struct panthor_file *pfile,
 	INIT_WORK(&group->tiler_oom_work, group_tiler_oom_work);
 	INIT_WORK(&group->release_work, group_release_work);
 
+	group->pfile = panthor_file_get(pfile);
+
 	group->vm = panthor_vm_pool_get_vm(pfile->vms, group_args->vm_id);
 	if (!group->vm) {
 		ret = -EINVAL;
-- 
2.50.0.714.g196bf9f422-goog