4.2.8-ckt2 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> commit 0f0cd472062eca6f9fac8be0cd5585f9a2df1ab2 upstream. Limit busywaiting only to the request currently being processed by the GPU. If the request is not currently being processed by the GPU, there is a very low likelihood of it being completed within the 2 microsecond spin timeout and so we will just be wasting CPU cycles. v2: Check for logical inversion when rebasing - we were incorrectly checking for this request being active, and instead busywaiting for when the GPU was not yet processing the request of interest. v3: Try another colour for the seqno names. v4: Another colour for the function names. v5: Remove the forced coherency when checking for the active request. On reflection and plenty of recent experimentation, the issue is not a cache coherency problem - but an irq/seqno ordering problem (timing issue). Here, we do not need the w/a to force ordering of the read with an interrupt. Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> Cc: "Rogozhkin, Dmitry V" <dmitry.v.rogozhkin@xxxxxxxxx> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> Cc: Eero Tamminen <eero.t.tamminen@xxxxxxxxx> Cc: "Rantala, Valtteri" <valtteri.rantala@xxxxxxxxx> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> Link: http://patchwork.freedesktop.org/patch/msgid/1449833608-22125-4-git-send-email-chris@xxxxxxxxxxxxxxxxxx (cherry picked from commit 821485dc2ad665f136c57ee589bf7a8210160fe2) Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx> --- drivers/gpu/drm/i915/i915_drv.h | 27 +++++++++++++++++++-------- drivers/gpu/drm/i915/i915_gem.c | 8 +++++++- 2 files changed, 26 insertions(+), 9 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index e1df8feb..f4e2f54 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -2119,8 +2119,17 @@ struct drm_i915_gem_request { struct drm_i915_private *i915; struct intel_engine_cs *ring; - /** GEM sequence number associated with this request. */ - uint32_t seqno; + /** GEM sequence number associated with the previous request, + * when the HWS breadcrumb is equal to this the GPU is processing + * this request. + */ + u32 previous_seqno; + + /** GEM sequence number associated with this request, + * when the HWS breadcrumb is equal or greater than this the GPU + * has finished processing this request. + */ + u32 seqno; /** Position in the ringbuffer of the start of the request */ u32 head; @@ -2797,15 +2806,17 @@ i915_seqno_passed(uint32_t seq1, uint32_t seq2) return (int32_t)(seq1 - seq2) >= 0; } +static inline bool i915_gem_request_started(struct drm_i915_gem_request *req, + bool lazy_coherency) +{ + u32 seqno = req->ring->get_seqno(req->ring, lazy_coherency); + return i915_seqno_passed(seqno, req->previous_seqno); +} + static inline bool i915_gem_request_completed(struct drm_i915_gem_request *req, bool lazy_coherency) { - u32 seqno; - - BUG_ON(req == NULL); - - seqno = req->ring->get_seqno(req->ring, lazy_coherency); - + u32 seqno = req->ring->get_seqno(req->ring, lazy_coherency); return i915_seqno_passed(seqno, req->seqno); } diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index ace38a7..da7653c 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -1221,9 +1221,13 @@ static int __i915_spin_request(struct drm_i915_gem_request *req, int state) * takes to sleep on a request, on the order of a microsecond. */ - if (i915_gem_request_get_ring(req)->irq_refcount) + if (req->ring->irq_refcount) return -EBUSY; + /* Only spin if we know the GPU is processing this request */ + if (!i915_gem_request_started(req, true)) + return -EAGAIN; + timeout = local_clock_us(&cpu) + 5; while (!need_resched()) { if (i915_gem_request_completed(req, true)) @@ -1237,6 +1241,7 @@ static int __i915_spin_request(struct drm_i915_gem_request *req, int state) cpu_relax_lowlatency(); } + if (i915_gem_request_completed(req, false)) return 0; @@ -2594,6 +2599,7 @@ int __i915_add_request(struct intel_engine_cs *ring, } request->emitted_jiffies = jiffies; + request->previous_seqno = ring->last_submitted_seqno; ring->last_submitted_seqno = request->seqno; list_add_tail(&request->list, &ring->request_list); request->file_priv = NULL; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html