drm/v3d: Set job pointer to NULL when the job's fence has an error

Similar to commit e4b5ccd ("drm/v3d: Ensure job pointer is set to
NULL after job completion"), ensure the job pointer is set to `NULL` when
a job's fence has an error. Failing to do so can trigger kernel warnings
in specific scenarios, such as:

1. v3d_csd_job_run() assigns `v3d->csd_job = job`
2. CSD job exceeds hang limit, causing a timeout → v3d_gpu_reset_for_timeout()
3. GPU reset
4. drm_sched_resubmit_jobs() sets the job's fence to `-ECANCELED`.
5. v3d_csd_job_run() detects the fence error and returns NULL, not
   submitting the job to the GPU
6. User-space runs `modprobe -r v3d`
7. v3d_gem_destroy()

v3d_gem_destroy() triggers a warning indicating that the CSD job never
ended, as we didn't set `v3d->csd_job` to NULL after the timeout. The same
can also happen to BIN, RENDER, and TFU jobs.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250313-v3d-gpu-reset-fixes-v4-2-c1e780d8e096@igalia.com

drivers/gpu/drm/v3d/v3d_sched.c

@@ -226,8 +226,12 @@ static struct dma_fence *v3d_bin_job_run(struct drm_sched_job *sched_job)
 	struct dma_fence *fence;
 	unsigned long irqflags;
 
-	if (unlikely(job->base.base.s_fence->finished.error))
+	if (unlikely(job->base.base.s_fence->finished.error)) {
+		spin_lock_irqsave(&v3d->job_lock, irqflags);
+		v3d->bin_job = NULL;
+		spin_unlock_irqrestore(&v3d->job_lock, irqflags);
 		return NULL;
+	}
 
 	/* Lock required around bin_job update vs
 	 * v3d_overflow_mem_work().
@@ -281,8 +285,10 @@ static struct dma_fence *v3d_render_job_run(struct drm_sched_job *sched_job)
 	struct drm_device *dev = &v3d->drm;
 	struct dma_fence *fence;
 
-	if (unlikely(job->base.base.s_fence->finished.error))
+	if (unlikely(job->base.base.s_fence->finished.error)) {
+		v3d->render_job = NULL;
 		return NULL;
+	}
 
 	v3d->render_job = job;
 
@@ -327,8 +333,10 @@ v3d_tfu_job_run(struct drm_sched_job *sched_job)
 	struct drm_device *dev = &v3d->drm;
 	struct dma_fence *fence;
 
-	if (unlikely(job->base.base.s_fence->finished.error))
+	if (unlikely(job->base.base.s_fence->finished.error)) {
+		v3d->tfu_job = NULL;
 		return NULL;
+	}
 
 	v3d->tfu_job = job;
 
@@ -373,8 +381,10 @@ v3d_csd_job_run(struct drm_sched_job *sched_job)
 	struct dma_fence *fence;
 	int i, csd_cfg0_reg;
 
-	if (unlikely(job->base.base.s_fence->finished.error))
+	if (unlikely(job->base.base.s_fence->finished.error)) {
+		v3d->csd_job = NULL;
 		return NULL;
+	}
 
 	v3d->csd_job = job;