drm/i915: add HAS_ALIASING_PPGTT parameter for userspace

On Sanybridge a few MI read/write commands only work when ppgtt is
enabled.  Userspace therefore needs to be able to check whether ppgtt
is enabled. For added hilarity, you need to reset the "use global GTT"
bit on snb when ppgtt is enabled, otherwise it won't work.  Despite
what bspec says about automatically using ppgtt ...

Luckily PIPE_CONTROL (the only write cmd current userspace uses) is
not affected by all this, as tested by tests/gem_pipe_control_store_loop.

Reviewed-and-tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

2 files changed, 5 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 3c086d707a91..fdff0097cf2b 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -790,6 +790,9 @@ static int i915_getparam(struct drm_device *dev, void *data,
         case I915_PARAM_HAS_LLC:
                 value = HAS_LLC(dev);
                 break;
+        case I915_PARAM_HAS_ALIASING_PPGTT:
+                value = dev_priv->mm.aliasing_ppgtt ? 1 : 0;
+                break;
         default:
                 DRM_DEBUG_DRIVER("Unknown parameter %d\n",
                                  param->param);
diff --git a/include/drm/i915_drm.h b/include/drm/i915_drm.h
index da929bb5b788..f3f82242bf1d 100644
--- a/include/drm/i915_drm.h
+++ b/include/drm/i915_drm.h
@@ -296,7 +296,8 @@ typedef struct drm_i915_irq_wait {
 #define I915_PARAM_HAS_EXEC_CONSTANTS    14
 #define I915_PARAM_HAS_RELAXED_DELTA     15
 #define I915_PARAM_HAS_GEN7_SOL_RESET    16
-#define I915_PARAM_HAS_LLC       17
+#define I915_PARAM_HAS_LLC               17
+#define I915_PARAM_HAS_ALIASING_PPGTT    18
 
 typedef struct drm_i915_getparam {
         int param;