drm/i915: Allow disabling error capture

We currently capture the GPU state after we detect a hang. This is vital
for us to both triage and debug hangs in the wild (post-mortem
debugging). However, it comes at the cost of running some potentially
dangerous code (since it has to make very few assumption about the state
of the driver) that is quite resource intensive.

This patch introduces both a method to disable error capture at runtime
(for users who hit bugs at runtime and need a workaround) and to disable
error capture at compiletime (for realtime users who want to minimise
any possible latency, and never require error capture, saving ~30k of
code). The cost is that we now have to be wary of (and test!) a kconfig
flag and a module parameter. The effect of the module parameter is easy
to verify through code inspection and runtime testing, but a kconfig flag
needs regular compile checking.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: Jani Nikula <jani.nikula@linux.intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch
Link: http://patchwork.freedesktop.org/patch/msgid/20161012090522.367-2-chris@chris-wilson.co.uk

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index 7769e469118f..8844b99bd760 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -46,6 +46,19 @@ config DRM_I915_PRELIMINARY_HW_SUPPORT
 
 	  If in doubt, say "N".
 
+config DRM_I915_CAPTURE_ERROR
+	bool "Enable capturing GPU state following a hang"
+	depends on DRM_I915
+	default y
+	help
+	  This option enables capturing the GPU state when a hang is detected.
+	  This information is vital for triaging hangs and assists in debugging.
+	  Please report any hang to
+            https://bugs.freedesktop.org/enter_bug.cgi?product=DRI
+	  for triaging.
+
+	  If in doubt, say "Y".
+
 config DRM_I915_USERPTR
 	bool "Always enable userptr support"
 	depends on DRM_I915