linux-kernel - [PATCH v6 1/3] drm/sched: Adjust outdated docu for run

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Message-ID: <20250224120104.26211-3-phasta@kernel.org>
Date: Mon, 24 Feb 2025 13:01:03 +0100
From: Philipp Stanner <phasta@...nel.org>
To: Matthew Brost <matthew.brost@...el.com>,
	Danilo Krummrich <dakr@...nel.org>,
	Philipp Stanner <phasta@...nel.org>,
	Christian König <ckoenig.leichtzumerken@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
Cc: dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v6 1/3] drm/sched: Adjust outdated docu for run_job()

The documentation for drm_sched_backend_ops.run_job() mentions a certain
function called drm_sched_job_recovery(). This function does not exist.
What's actually meant is drm_sched_resubmit_jobs(), which is by now also
deprecated.

Remove the mention of the removed function.

Discourage the behavior of drm_sched_backend_ops.run_job() being called
multiple times for the same job.

Signed-off-by: Philipp Stanner <phasta@...nel.org>
---
 include/drm/gpu_scheduler.h | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index 6bf458dbce84..5d0394f40aae 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -420,10 +420,33 @@ struct drm_sched_backend_ops {
 					 struct drm_sched_entity *s_entity);
 
 	/**
-         * @run_job: Called to execute the job once all of the dependencies
-         * have been resolved.  This may be called multiple times, if
-	 * timedout_job() has happened and drm_sched_job_recovery()
-	 * decides to try it again.
+	 * @run_job: Called to execute the job once all of the dependencies
+	 * have been resolved.
+	 *
+	 * @sched_job: the job to run
+	 *
+	 * The deprecated drm_sched_resubmit_jobs() (called by
+	 * &drm_sched_backend_ops.timedout_job) can invoke this again with the
+	 * same parameters. Using this is discouraged because it, presumably,
+	 * violates dma_fence rules.
+	 *
+	 * TODO: Document which fence rules above.
+	 *
+	 * This method is called in a workqueue context - either from the
+	 * submit_wq the driver passed through drm_sched_init(), or, if the
+	 * driver passed NULL, a separate, ordered workqueue the scheduler
+	 * allocated.
+	 *
+	 * Note that the scheduler expects to 'inherit' its own reference to
+	 * this fence from the callback. It does not invoke an extra
+	 * dma_fence_get() on it. Consequently, this callback must take a
+	 * reference for the scheduler, and additional ones for the driver's
+	 * respective needs.
+	 *
+	 * Return:
+	 * * On success: dma_fence the driver must signal once the hardware has
+	 * completed the job ("hardware fence").
+	 * * On failure: NULL or an ERR_PTR.
 	 */
 	struct dma_fence *(*run_job)(struct drm_sched_job *sched_job);
 
-- 
2.48.1