[Intel-gfx] [PATCH 54/66] drm/i915: USE LRI for switching PP_DIR_BASE

[Ben Widawsky]

The docs seem to suggest this is the appropriate method (though it
doesn't say so outright). We certainly must do this for switching VMs on
the fly, since synchronizing the rings to MMIO updates isn't acceptable.

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 583d136..be5c7a9 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -171,13 +171,44 @@ static int gen6_ppgtt_enable(struct i915_hw_ppgtt *ppgtt)
 		/* GFX_MODE is per-ring on gen7+ */
 	}
 
+	POSTING_READ(GAM_ECOCHK);
 	for_each_ring(ring, dev_priv, i) {
+		int ret;
+
 		if (INTEL_INFO(dev)->gen >= 7)
 			I915_WRITE(RING_MODE_GEN7(ring),
 				   _MASKED_BIT_ENABLE(GFX_PPGTT_ENABLE));
 
-		I915_WRITE(RING_PP_DIR_DCLV(ring), PP_DIR_DCLV_2G);
-		I915_WRITE(RING_PP_DIR_BASE(ring), pd_offset);
+		/* If we're in reset, we can assume the GPU is sufficiently idle
+		 * to manually frob these bits. Ideally we could use the ring
+		 * functions, except our error handling makes it quite difficult
+		 * (can't use intel_ring_begin, ring->flush, or
+		 * intel_ring_advance)
+		 */
+		if (i915_reset_in_progress(&dev_priv->gpu_error)) {
+			WARN_ON(ppgtt != dev_priv->gtt.aliasing_ppgtt);
+			I915_WRITE(RING_PP_DIR_DCLV(ring), PP_DIR_DCLV_2G);
+			I915_WRITE(RING_PP_DIR_BASE(ring), pd_offset);
+			return 0;
+		}
+
+		/* NB: TLBs must be flushed and invalidated before a switch */
+		ret = ring->flush(ring, I915_GEM_GPU_DOMAINS,
+				  I915_GEM_GPU_DOMAINS);
+		if (ret)
+			return ret;
+
+		ret = intel_ring_begin(ring, 6);
+		if (ret)
+			return ret;
+
+		intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(2));
+		intel_ring_emit(ring, RING_PP_DIR_DCLV(ring));
+		intel_ring_emit(ring, PP_DIR_DCLV_2G);
+		intel_ring_emit(ring, RING_PP_DIR_BASE(ring));
+		intel_ring_emit(ring, pd_offset);
+		intel_ring_emit(ring, MI_NOOP);
+		intel_ring_advance(ring);
 	}
 	return 0;
 }
-- 
1.8.3.1