[Intel-gfx] [PATCH] drm/i915/cnl: Use mmio access to context status buffer

[Mika Kuoppala]

Evidence indicates that Cannonlake HWSP is not coherent
as it should. Revert to using mmio access for now.

Testcase: igt/gem_ctx_switch
References: https://bugs.freedesktop.org/show_bug.cgi?id=105888
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Rafael Antognolli <rafael.antognolli at intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_engine_cs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 68898d58dd1e..1a8370779bbb 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -475,6 +475,9 @@ static bool csb_force_mmio(struct drm_i915_private *i915)
 	if (intel_vgpu_active(i915) && !intel_vgpu_has_hwsp_emulation(i915))
 		return true;
 
+	if (IS_CANNONLAKE(i915))
+		return true;
+
 	return false;
 }
 
-- 
2.14.1