drm/i915/guc: Preemption! With GuC

Pretty similar to what we have on execlists.
We're reusing most of the GEM code, however, due to GuC quirks we need a
couple of extra bits.
Preemption is implemented as GuC action, and actions can be pretty slow.
Because of that, we're using a mutex to serialize them. Since we're
requesting preemption from the tasklet, the task of creating a workitem
and wrapping it in GuC action is delegated to a worker.

To distinguish that preemption has finished, we're using additional
piece of HWSP, and since we're not getting context switch interrupts,
we're also adding a user interrupt.

The fact that our special preempt context has completed unfortunately
doesn't mean that we're ready to submit new work. We also need to wait
for GuC to finish its own processing.

v2: Don't compile out the wait for GuC, handle workqueue flush on reset,
no need for ordered workqueue, put on a reviewer hat when looking at my own
patches (Chris)
Move struct work around in intel_guc, move user interruput outside of
conditional (Michał)
Keep ring around rather than chase though intel_context

v3: Extract WA for flushing ggtt writes to a helper (Chris)
Keep work_struct in intel_guc rather than engine (Michał)
Use ordered workqueue for inject_preempt worker to avoid GuC quirks.

v4: Drop now unused INTEL_GUC_PREEMPT_OPTION_IMMEDIATE (Daniele)
Drop stray newlines, use container_of for intel_guc in worker,
check for presence of workqueue when flushing it, rather than
enable_guc_submission modparam, reorder preempt postprocessing (Chris)

v5: Make wq NULL after destroying it

v6: Swap struct guc_preempt_work members (Michał)

Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171026133558.19580-1-michal.winiarski@intel.com

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_guc.h b/drivers/gpu/drm/i915/intel_guc.h
index 6ca55c5bed3c..607e02500262 100644
--- a/drivers/gpu/drm/i915/intel_guc.h
+++ b/drivers/gpu/drm/i915/intel_guc.h
@@ -34,6 +34,11 @@
 #include "i915_guc_reg.h"
 #include "i915_vma.h"
 
+struct guc_preempt_work {
+	struct work_struct work;
+	struct intel_engine_cs *engine;
+};
+
 /*
  * Top level structure of GuC. It handles firmware loading and manages client
  * pool and doorbells. intel_guc owns a i915_guc_client to replace the legacy
@@ -60,6 +65,9 @@ struct intel_guc {
 	struct i915_guc_client *execbuf_client;
 	struct i915_guc_client *preempt_client;
 
+	struct guc_preempt_work preempt_work[I915_NUM_ENGINES];
+	struct workqueue_struct *preempt_wq;
+
 	DECLARE_BITMAP(doorbell_bitmap, GUC_NUM_DOORBELLS);
 	/* Cyclic counter mod pagesize	*/
 	u32 db_cacheline;