drm/i915: re-use computed offset bias for context pin

The context has to obey the same offset requirements as the ring,
so we can re-use the same bias value we computed for the ring instead of
unconditionally using GUC_WOPCM_TOP.

Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1482537382-28584-2-git-send-email-daniele.ceraolospurio@intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_lrc.c

@@ -782,7 +782,9 @@ static int execlists_context_pin(struct intel_engine_cs *engine,
 			goto err;
 	}
 
-	flags = PIN_OFFSET_BIAS | GUC_WOPCM_TOP | PIN_GLOBAL;
+	flags = PIN_GLOBAL;
+	if (ctx->ggtt_offset_bias)
+		flags |= PIN_OFFSET_BIAS | ctx->ggtt_offset_bias;
 	if (ctx == ctx->i915->kernel_context)
 		flags |= PIN_HIGH;