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authorMatthew Brost2021-06-29 12:35:10 -0700
committerDaniel Vetter2021-06-30 09:50:58 +0200
commitf587623b78ff538f5d9ef1241e58b91ea70a4daf (patch)
treecb5f61ff1f858c96d02eeaa8bb29d96db6d8ec69 /Documentation/gpu
parent53fe9cf2dafe2b0382a4e682e4eebe0a442dcb5a (diff)
drm/doc/rfc: i915 GuC submission / DRM scheduler
Add entry for i915 GuC submission / DRM scheduler integration plan. Follow up patch with details of new parallel submission uAPI to come. v2: (Daniel Vetter) - Expand explaination of why bonding isn't supported for GuC submission - CC some of the DRM scheduler maintainers - Add priority inheritance / boosting use case - Add reasoning for removing in order assumptions (Daniel Stone) - Add links to priority spec v4: (Tvrtko) - Add TODOs section (Daniel Vetter) - Pull in 1 line from following patch v5: (Checkpatch) - Fix typos Cc: Christian König <christian.koenig@amd.com> Cc: Luben Tuikov <luben.tuikov@amd.com> Cc: Alex Deucher <alexander.deucher@amd.com> Cc: Steven Price <steven.price@arm.com> Cc: Jon Bloomfield <jon.bloomfield@intel.com> Cc: Dave Airlie <airlied@gmail.com> Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Jason Ekstrand <jason@jlekstrand.net> Cc: dri-devel@lists.freedesktop.org Signed-off-by: Matthew Brost <matthew.brost@intel.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: Dave Airlie <airlied@redhat.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20210629193511.124099-2-matthew.brost@intel.com
Diffstat (limited to 'Documentation/gpu')
-rw-r--r--Documentation/gpu/rfc/i915_scheduler.rst91
-rw-r--r--Documentation/gpu/rfc/index.rst4
2 files changed, 95 insertions, 0 deletions
diff --git a/Documentation/gpu/rfc/i915_scheduler.rst b/Documentation/gpu/rfc/i915_scheduler.rst
new file mode 100644
index 000000000000..7acd386a6b49
--- /dev/null
+++ b/Documentation/gpu/rfc/i915_scheduler.rst
@@ -0,0 +1,91 @@
+=========================================
+I915 GuC Submission/DRM Scheduler Section
+=========================================
+
+Upstream plan
+=============
+For upstream the overall plan for landing GuC submission and integrating the
+i915 with the DRM scheduler is:
+
+* Merge basic GuC submission
+ * Basic submission support for all gen11+ platforms
+ * Not enabled by default on any current platforms but can be enabled via
+ modparam enable_guc
+ * Lots of rework will need to be done to integrate with DRM scheduler so
+ no need to nit pick everything in the code, it just should be
+ functional, no major coding style / layering errors, and not regress
+ execlists
+ * Update IGTs / selftests as needed to work with GuC submission
+ * Enable CI on supported platforms for a baseline
+ * Rework / get CI heathly for GuC submission in place as needed
+* Merge new parallel submission uAPI
+ * Bonding uAPI completely incompatible with GuC submission, plus it has
+ severe design issues in general, which is why we want to retire it no
+ matter what
+ * New uAPI adds I915_CONTEXT_ENGINES_EXT_PARALLEL context setup step
+ which configures a slot with N contexts
+ * After I915_CONTEXT_ENGINES_EXT_PARALLEL a user can submit N batches to
+ a slot in a single execbuf IOCTL and the batches run on the GPU in
+ paralllel
+ * Initially only for GuC submission but execlists can be supported if
+ needed
+* Convert the i915 to use the DRM scheduler
+ * GuC submission backend fully integrated with DRM scheduler
+ * All request queues removed from backend (e.g. all backpressure
+ handled in DRM scheduler)
+ * Resets / cancels hook in DRM scheduler
+ * Watchdog hooks into DRM scheduler
+ * Lots of complexity of the GuC backend can be pulled out once
+ integrated with DRM scheduler (e.g. state machine gets
+ simplier, locking gets simplier, etc...)
+ * Execlists backend will minimum required to hook in the DRM scheduler
+ * Legacy interface
+ * Features like timeslicing / preemption / virtual engines would
+ be difficult to integrate with the DRM scheduler and these
+ features are not required for GuC submission as the GuC does
+ these things for us
+ * ROI low on fully integrating into DRM scheduler
+ * Fully integrating would add lots of complexity to DRM
+ scheduler
+ * Port i915 priority inheritance / boosting feature in DRM scheduler
+ * Used for i915 page flip, may be useful to other DRM drivers as
+ well
+ * Will be an optional feature in the DRM scheduler
+ * Remove in-order completion assumptions from DRM scheduler
+ * Even when using the DRM scheduler the backends will handle
+ preemption, timeslicing, etc... so it is possible for jobs to
+ finish out of order
+ * Pull out i915 priority levels and use DRM priority levels
+ * Optimize DRM scheduler as needed
+
+TODOs for GuC submission upstream
+=================================
+
+* Need an update to GuC firmware / i915 to enable error state capture
+* Open source tool to decode GuC logs
+* Public GuC spec
+
+New uAPI for basic GuC submission
+=================================
+No major changes are required to the uAPI for basic GuC submission. The only
+change is a new scheduler attribute: I915_SCHEDULER_CAP_STATIC_PRIORITY_MAP.
+This attribute indicates the 2k i915 user priority levels are statically mapped
+into 3 levels as follows:
+
+* -1k to -1 Low priority
+* 0 Medium priority
+* 1 to 1k High priority
+
+This is needed because the GuC only has 4 priority bands. The highest priority
+band is reserved with the kernel. This aligns with the DRM scheduler priority
+levels too.
+
+Spec references:
+----------------
+* https://www.khronos.org/registry/EGL/extensions/IMG/EGL_IMG_context_priority.txt
+* https://www.khronos.org/registry/vulkan/specs/1.2-extensions/html/chap5.html#devsandqueues-priority
+* https://spec.oneapi.com/level-zero/latest/core/api.html#ze-command-queue-priority-t
+
+New parallel submission uAPI
+============================
+Details to come in a following patch.
diff --git a/Documentation/gpu/rfc/index.rst b/Documentation/gpu/rfc/index.rst
index 05670442ca1b..91e93a705230 100644
--- a/Documentation/gpu/rfc/index.rst
+++ b/Documentation/gpu/rfc/index.rst
@@ -19,3 +19,7 @@ host such documentation:
.. toctree::
i915_gem_lmem.rst
+
+.. toctree::
+
+ i915_scheduler.rst