On Thu, 20 Jan 2022, Matthew Brost <matthew.brost@xxxxxxxxx> wrote: > 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. > > v2: > (CI) > - Fix build error (hide corrupted label in write function behind > CONFIG_DRM_I915_DEBUG_GUC) > > Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx> > --- > drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 6 ++++++ > 1 file changed, 6 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..948cf31429412 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 Please don't add #ifdefs inline. You can use IS_ENABLED(CONFIG_DRM_I915_DEBUG_GUC) in if statements, but otherwise the code needs to be split out to a separate function. BR, Jani. > > GEM_BUG_ON(tail > size); > > @@ -445,11 +447,13 @@ static int ct_write(struct intel_guc_ct *ct, > > return 0; > > +#ifdef CONFIG_DRM_I915_DEBUG_GUC > corrupted: > CT_ERROR(ct, "Corrupted descriptor head=%u tail=%u status=%#x\n", > desc->head, desc->tail, desc->status); > ctb->broken = true; > return -EPIPE; > +#endif > } > > /** > @@ -815,8 +819,10 @@ 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); -- Jani Nikula, Intel Open Source Graphics Center
