Don't check CT descriptor status, unless CONFIG_DRM_I915_DEBUG_GUC is set, before CT write / read as this could result in a read across the PCIe bus thus adding latency to every CT write / read. On well behavied systems this vaue should always read as zero. For some reason it doesn't the CT channel is broken and will eventually recover from a GT reset, albeit the GT reset will not be triggered immediately by seeing that descriptor status is non-zero.
Signed-off-by: Matthew Brost <[email protected]> --- drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c index de89d40abd38d..18af99a802f64 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c @@ -379,8 +379,10 @@ static int ct_write(struct intel_guc_ct *ct, u32 *cmds = ctb->cmds; unsigned int i; +#ifdef CONFIG_DRM_I915_DEBUG_GUC if (unlikely(desc->status)) goto corrupted; +#endif GEM_BUG_ON(tail > size); @@ -815,8 +817,10 @@ static int ct_read(struct intel_guc_ct *ct, struct ct_incoming_msg **msg) if (unlikely(ctb->broken)) return -EPIPE; +#ifdef CONFIG_DRM_I915_DEBUG_GUC if (unlikely(desc->status)) goto corrupted; +#endif GEM_BUG_ON(head > size); -- 2.34.1
