[Intel-gfx] [PATCH] drm/i915: Allow unready gpu to be reset on gen8

[Mika Kuoppala]

Gen9 has had demonstrated cases where forcing a not ready gpu
into reset has caused system hang [1].

Gen8 has never to this date demonstrated such behaviour.

In our CI tests bsw sometimes ends up in a state where it claims it
is not ready for reset, based on reset request, after gpu hang.

Allow gen8 to reset even after claims of nonreadiness in order
to keep the gpu accessible. Enhance logging so that it will be
clear what conditions led to decision of proceeding or bailing out,
so that we will spot if this way of forcing our will against gpu turns
out to be foolhardy.

References [1]: https://bugs.freedesktop.org/show_bug.cgi?id=89959
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Tomi Sarvela <tomix.p.sarvela at intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/intel_uncore.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index f0f97b2..47c17f2 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1504,7 +1504,14 @@ not_ready:
 		I915_WRITE(RING_RESET_CTL(engine->mmio_base),
 			   _MASKED_BIT_DISABLE(RESET_CTL_REQUEST_RESET));
 
-	return -EIO;
+	if (INTEL_INFO(dev)->gen == 9) {
+		DRM_ERROR("Reset would risk system stability, bailing out\n");
+		return -EIO;
+	}
+
+	DRM_ERROR("Forcing non ready gpu into reset\n");
+
+	return gen6_do_reset(dev);
 }
 
 static int (*intel_get_gpu_reset(struct drm_device *dev))(struct drm_device *)
-- 
2.5.0