drm/i915: Prevent machine hang from Broxton's vtd w/a and error capture

Since capturing the error state requires fiddling around with the GGTT
to read arbitrary buffers and is itself run under stop_machine(), it
deadlocks the machine (effectively a hard hang) when run in conjunction
with Broxton's VTd workaround to serialize GGTT access.

v2: Store the ERR_PTR in first_error so that the error can be reported
to the user via sysfs.
v3: Mention the quirk in dmesg (using info as per usual)

Fixes: 0ef34ad6222a ("drm/i915: Serialize GTT/Aperture accesses on BXT")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: John Harrison <john.C.Harrison@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181102161232.17742-5-chris@chris-wilson.co.uk

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_gpu_error.h b/drivers/gpu/drm/i915/i915_gpu_error.h
index 8710fb18ed74..3ec89a504de5 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.h
+++ b/drivers/gpu/drm/i915/i915_gpu_error.h
@@ -343,6 +343,7 @@ static inline void i915_gpu_state_put(struct i915_gpu_state *gpu)
 
 struct i915_gpu_state *i915_first_error_state(struct drm_i915_private *i915);
 void i915_reset_error_state(struct drm_i915_private *i915);
+void i915_disable_error_state(struct drm_i915_private *i915, int err);
 
 #else
 
@@ -355,13 +356,18 @@ static inline void i915_capture_error_state(struct drm_i915_private *dev_priv,
 static inline struct i915_gpu_state *
 i915_first_error_state(struct drm_i915_private *i915)
 {
-        return NULL;
+        return ERR_PTR(-ENODEV);
 }
 
 static inline void i915_reset_error_state(struct drm_i915_private *i915)
 {
 }
 
+static inline void i915_disable_error_state(struct drm_i915_private *i915,
+                                            int err)
+{
+}
+
 #endif /* IS_ENABLED(CONFIG_DRM_I915_CAPTURE_ERROR) */
 
 #endif /* _I915_GPU_ERROR_H_ */