[PATCH v3] drm/panthor: Fix couple of NULL vs IS_ERR() bugs

[Harshit Mogalapalli]

Currently panthor_vm_get_heap_pool() returns both ERR_PTR() and
NULL(when create is false and if there is no poool attached to the
VM)
        - Change the function to return error pointers, when pool is
          NULL return -ENOENT
        - Also handle the callers to check for IS_ERR() on failure.

Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapa...@oracle.com>
---
This is spotted by smatch and the patch is only compile tested

v1->v2: Fix the function panthor_vm_get_heap_pool() to only return error
pointers and handle the caller sites [Suggested by Boris Brezillon]
        - Also merge these IS_ERR() vs NULL bugs into same patch

v2->v3: pull out error checking for devm_drm_dev_alloc() failure.
---
 drivers/gpu/drm/panthor/panthor_drv.c   | 4 ++--
 drivers/gpu/drm/panthor/panthor_mmu.c   | 2 ++
 drivers/gpu/drm/panthor/panthor_sched.c | 2 +-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_drv.c 
b/drivers/gpu/drm/panthor/panthor_drv.c
index 11b3ccd58f85..050b905b0453 100644
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -1090,8 +1090,8 @@ static int panthor_ioctl_tiler_heap_destroy(struct 
drm_device *ddev, void *data,
                return -EINVAL;
 
        pool = panthor_vm_get_heap_pool(vm, false);
-       if (!pool) {
-               ret = -EINVAL;
+       if (IS_ERR(pool)) {
+               ret = PTR_ERR(pool);
                goto out_put_vm;
        }
 
diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c 
b/drivers/gpu/drm/panthor/panthor_mmu.c
index fdd35249169f..e1285cdb09ff 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -1893,6 +1893,8 @@ struct panthor_heap_pool *panthor_vm_get_heap_pool(struct 
panthor_vm *vm, bool c
                        vm->heaps.pool = panthor_heap_pool_get(pool);
        } else {
                pool = panthor_heap_pool_get(vm->heaps.pool);
+               if (!pool)
+                       pool = ERR_PTR(-ENOENT);
        }
        mutex_unlock(&vm->heaps.lock);
 
diff --git a/drivers/gpu/drm/panthor/panthor_sched.c 
b/drivers/gpu/drm/panthor/panthor_sched.c
index 5f7803b6fc48..617df2b980d0 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -1343,7 +1343,7 @@ static int group_process_tiler_oom(struct panthor_group 
*group, u32 cs_id)
        if (unlikely(csg_id < 0))
                return 0;
 
-       if (!heaps || frag_end > vt_end || vt_end >= vt_start) {
+       if (IS_ERR(heaps) || frag_end > vt_end || vt_end >= vt_start) {
                ret = -EINVAL;
        } else {
                /* We do the allocation without holding the scheduler lock to 
avoid
-- 
2.39.3