drm/i915: Remove unnecessary ggtt_offset_bias from i915_gem_context

Since ggtt_offset_bias is now stored in ggtt.pin_bias, it is duplicated
inside i915_gem_context, and can instead be accessed directly from ggtt.

v3:
Added a helper function to retrieve the ggtt.pin_bias from the vma.

v4:
Moved the helper function to the previous patch in the series.
Dropped the bias from intel_ring_pin. This introduces a slight functional
change since we are always pinning the ring a bit higher if GuC is present
even though we don't really need to.

v8:
Fixed patch not applying on the most recent upstream.

Signed-off-by: Jakub Bartmiński <jakub.bartminski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@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/20180727141148.30874-4-jakub.bartminski@intel.com
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 66c7252..7879791 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1303,8 +1303,7 @@ static int __context_pin(struct i915_gem_context *ctx, struct i915_vma *vma)
 	}
 
 	flags = PIN_GLOBAL | PIN_HIGH;
-	if (ctx->ggtt_offset_bias)
-		flags |= PIN_OFFSET_BIAS | ctx->ggtt_offset_bias;
+	flags |= PIN_OFFSET_BIAS | i915_ggtt_pin_bias(vma);
 
 	return i915_vma_pin(vma, 0, 0, flags);
 }
@@ -1332,7 +1331,7 @@ __execlists_context_pin(struct intel_engine_cs *engine,
 		goto unpin_vma;
 	}
 
-	ret = intel_ring_pin(ce->ring, ctx->i915, ctx->ggtt_offset_bias);
+	ret = intel_ring_pin(ce->ring, ctx->i915);
 	if (ret)
 		goto unpin_map;