drm/i915: Ivybridge MI_ARB_ON_OFF context w/a

The workaround itself applies to gen7 only (according to the docs) and
as Eric Anholt points out shouldn't be required since we don't use HW
scheduling features, and therefore arbitration. Though since it is a
small, and simple addition, and we don't really understand the issue,
just do it.

FWIW, I eventually want to play with some of the arbitration stuff, and
I'd hate to forget about this.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index fb6aa5e10991d5e1d78d3dc891751622081c0554..d49d5fc0a592ff61c43dd9e9d99d319dc5fd5876 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -324,10 +324,15 @@ mi_set_context(struct intel_ring_buffer *ring,
 {
        int ret;
 
-       ret = intel_ring_begin(ring, 4);
+       ret = intel_ring_begin(ring, 6);
        if (ret)
                return ret;
 
+       if (IS_GEN7(ring->dev))
+               intel_ring_emit(ring, MI_ARB_ON_OFF | MI_ARB_DISABLE);
+       else
+               intel_ring_emit(ring, MI_NOOP);
+
        intel_ring_emit(ring, MI_NOOP);
        intel_ring_emit(ring, MI_SET_CONTEXT);
        intel_ring_emit(ring, new_context->obj->gtt_offset |
@@ -338,6 +343,11 @@ mi_set_context(struct intel_ring_buffer *ring,
        /* w/a: MI_SET_CONTEXT must always be followed by MI_NOOP */
        intel_ring_emit(ring, MI_NOOP);
 
+       if (IS_GEN7(ring->dev))
+               intel_ring_emit(ring, MI_ARB_ON_OFF | MI_ARB_ENABLE);
+       else
+               intel_ring_emit(ring, MI_NOOP);
+
        intel_ring_advance(ring);
 
        return ret;

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index bee1012081955d8b000a7152df1d9b161b98363a..14cb714df352dfc265231c0cad37b68821439763 100644 (file)
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -210,6 +210,9 @@
 #define MI_DISPLAY_FLIP                MI_INSTR(0x14, 2)
 #define MI_DISPLAY_FLIP_I915   MI_INSTR(0x14, 1)
 #define   MI_DISPLAY_FLIP_PLANE(n) ((n) << 20)
+#define MI_ARB_ON_OFF          MI_INSTR(0x08, 0)
+#define   MI_ARB_ENABLE                        (1<<0)
+#define   MI_ARB_DISABLE               (0<<0)
 #define MI_SET_CONTEXT         MI_INSTR(0x18, 0)
 #define   MI_MM_SPACE_GTT              (1<<8)
 #define   MI_MM_SPACE_PHYSICAL         (0<<8)