drm/panfrost: Handle error when allocating AS number

If we reach the beginning of the LRU AS list, then return an error.

Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
Link: https://lore.kernel.org/r/20251019145225.3621989-5-adrian.larumbe@collabora.com
Signed-off-by: Steven Price <steven.price@arm.com>

Author: larunbe

drivers/gpu/drm/panfrost/panfrost_job.c

@@ -217,7 +217,11 @@ static int panfrost_job_hw_submit(struct panfrost_job *job, int js)
 		goto err_hwsubmit;
 	}
 
-	cfg = panfrost_mmu_as_get(pfdev, job->mmu);
+	ret = panfrost_mmu_as_get(pfdev, job->mmu);
+	if (ret < 0)
+		goto err_hwsubmit;
+
+	cfg = ret;
 
 	panfrost_devfreq_record_busy(&pfdev->pfdevfreq);
 

drivers/gpu/drm/panfrost/panfrost_mmu.c

@@ -258,7 +258,7 @@ static int panfrost_mmu_cfg_init(struct panfrost_mmu *mmu,
 	}
 }
 
-u32 panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu)
+int panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu)
 {
 	int as;
 
@@ -300,7 +300,10 @@ u32 panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu)
 			if (!atomic_read(&lru_mmu->as_count))
 				break;
 		}
-		WARN_ON(&lru_mmu->list == &pfdev->as_lru_list);
+		if (WARN_ON(&lru_mmu->list == &pfdev->as_lru_list)) {
+			as = -EBUSY;
+			goto out;
+		}
 
 		list_del_init(&lru_mmu->list);
 		as = lru_mmu->as;

drivers/gpu/drm/panfrost/panfrost_mmu.h

@@ -16,7 +16,7 @@ void panfrost_mmu_fini(struct panfrost_device *pfdev);
 void panfrost_mmu_reset(struct panfrost_device *pfdev);
 void panfrost_mmu_suspend_irq(struct panfrost_device *pfdev);
 
-u32 panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu);
+int panfrost_mmu_as_get(struct panfrost_device *pfdev, struct panfrost_mmu *mmu);
 void panfrost_mmu_as_put(struct panfrost_device *pfdev, struct panfrost_mmu *mmu);
 
 struct panfrost_mmu *panfrost_mmu_ctx_get(struct panfrost_mmu *mmu);

drivers/gpu/drm/panfrost/panfrost_perfcnt.c

@@ -130,9 +130,11 @@ static int panfrost_perfcnt_enable_locked(struct panfrost_device *pfdev,
 		goto err_vunmap;
 	}
 
-	perfcnt->user = user;
+	ret = panfrost_mmu_as_get(pfdev, perfcnt->mapping->mmu);
+	if (ret < 0)
+		goto err_vunmap;
 
-	as = panfrost_mmu_as_get(pfdev, perfcnt->mapping->mmu);
+	as = ret;
 	cfg = GPU_PERFCNT_CFG_AS(as) |
 	      GPU_PERFCNT_CFG_MODE(GPU_PERFCNT_CFG_MODE_MANUAL);
 
@@ -164,6 +166,8 @@ static int panfrost_perfcnt_enable_locked(struct panfrost_device *pfdev,
 	/* The BO ref is retained by the mapping. */
 	drm_gem_object_put(&bo->base);
 
+	perfcnt->user = user;
+
 	return 0;
 
 err_vunmap: