[RFC 40/44] drm/i915: REVERTME Hack to allow IGT to test pre-emption

[John.C.Harrison@Intel.com]

From: John Harrison <John.C.Harrison@Intel.com>

In order to test pre-emption, a flag has been added to the execbuffer() API to
explicitly request that a given batch buffer is made pre-emptive. This is purely
a temporary measure to allow an IGT test to queue pre-emptive and non-preemptive
work loads.

Note that the final solution will be to add an IOCTL to set the priority of a
batch buffer (work in progress elsewhere). The scheduler will then decide to
pre-empt or not based on the assigned priority level.
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |   12 ++++++++++++
 include/uapi/drm/i915_drm.h                |    5 +++++
 2 files changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 81acdf2..b7d0737 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1361,6 +1361,18 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	qe.params.mask                    = mask;
 	qe.params.mode                    = mode;
 
+	/* Hack for testing pre-empting prior to having an official priority API */
+	if (qe.params.args_flags & I915_EXEC_PREEMPT) {
+#ifdef CONFIG_DRM_I915_SCHEDULER_PREEMPTION
+		struct i915_scheduler   *scheduler = dev_priv->scheduler;
+		qe.priority += scheduler->priority_level_preempt;
+#else
+		DRM_DEBUG("Buffer flags 0x%X includes PREEMPT!\n",
+			  qe.params.args_flags);
+#endif
+	}
+	/* Hack for testing pre-empting prior to having an official priority API */
+
 #ifdef CONFIG_DRM_I915_SCHEDULER
 	/*
 	 * Save away the list of objects used by this batch buffer for the
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index de6f603..d391222 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -694,6 +694,11 @@ struct drm_i915_gem_execbuffer2 {
 #define I915_EXEC_BLT                    (3<<0)
 #define I915_EXEC_VEBOX                  (4<<0)
 
+/* Pre-emption flag
+ * If this flag is set, this batchbuffer preempts those already submitted
+ */
+#define I915_EXEC_PREEMPT                (1<<5)
+
 /* Used for switching the constants addressing mode on gen4+ RENDER ring.
  * Gen6+ only supports relative addressing to dynamic state (default) and
  * absolute addressing.
-- 
1.7.9.5