Re: [PATCH 25/55] drm/i915: Update i915_gem_object_sync() to take a request structure

[John Harrison <John.C.Harrison@xxxxxxxxx>]

On 02/06/2015 19:26, Tomas Elf wrote:
> On 29/05/2015 17:43, John.C.Harrison@xxxxxxxxx wrote:
> > From: John Harrison <John.C.Harrison@xxxxxxxxx>
> >
> > The plan is to pass requests around as the basic submission tracking 
> > structure
> > rather than rings and contexts. This patch updates the 
> > i915_gem_object_sync()
> > code path.
> >
> > v2: Much more complex patch to share a single request between the 
> > sync and the
> > page flip. The _sync() function now supports lazy allocation of the 
> > request
> > structure. That is, if one is passed in then that will be used. If 
> > one is not,
> > then a request will be allocated and passed back out. Note that the 
> > _sync() code
> > does not necessarily require a request. Thus one will only be created 
> > until
> > certain situations. The reason the lazy allocation must be done 
> > within the
> > _sync() code itself is because the decision to need one or not is not 
> > really
> > something that code above can second guess (except in the case where 
> > one is
> > definitely not required because no ring is passed in).
> >
> > The call chains above _sync() now support passing a request through 
> > which most
> > callers passing in NULL and assuming that no request will be required 
> > (because
> > they also pass in NULL for the ring and therefore can't be generating 
> > any ring
> > code).
> >
> > The exeception is intel_crtc_page_flip() which now supports having a 
> > request
>
> 1. "The exeception" -> "The exception"
>
> > returned from _sync(). If one is, then that request is shared by the 
> > page flip
> > (if the page flip is of a type to need a request). If _sync() does 
> > not generate
> > a request but the page flip does need one, then the page flip path 
> > will create
> > its own request.
> >
> > v3: Updated comment description to be clearer about 'to_req' 
> > parameter (Tomas
> > Elf review request). Rebased onto newer tree that significantly 
> > changed the
> > synchronisation code.
> >
> > For: VIZ-5115
> > Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
> > ---
> >   drivers/gpu/drm/i915/i915_drv.h            |    4 ++-
> >   drivers/gpu/drm/i915/i915_gem.c            |   48 
> > +++++++++++++++++++++-------
> >   drivers/gpu/drm/i915/i915_gem_execbuffer.c |    2 +-
> >   drivers/gpu/drm/i915/intel_display.c       |   17 +++++++---
> >   drivers/gpu/drm/i915/intel_drv.h           |    3 +-
> >   drivers/gpu/drm/i915/intel_fbdev.c         |    2 +-
> >   drivers/gpu/drm/i915/intel_lrc.c           |    2 +-
> >   drivers/gpu/drm/i915/intel_overlay.c       |    2 +-
> >   8 files changed, 58 insertions(+), 22 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h 
> > b/drivers/gpu/drm/i915/i915_drv.h
> > index 64a10fa..f69e9cb 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -2778,7 +2778,8 @@ static inline void 
> > i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
> >
> >   int __must_check i915_mutex_lock_interruptible(struct drm_device 
> > *dev);
> >   int i915_gem_object_sync(struct drm_i915_gem_object *obj,
> > -             struct intel_engine_cs *to);
> > +             struct intel_engine_cs *to,
> > +             struct drm_i915_gem_request **to_req);
> >   void i915_vma_move_to_active(struct i915_vma *vma,
> >                    struct intel_engine_cs *ring);
> >   int i915_gem_dumb_create(struct drm_file *file_priv,
> > @@ -2889,6 +2890,7 @@ int __must_check
> >   i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> >                        u32 alignment,
> >                        struct intel_engine_cs *pipelined,
> > +                     struct drm_i915_gem_request **pipelined_request,
> >                        const struct i915_ggtt_view *view);
> >   void i915_gem_object_unpin_from_display_plane(struct 
> > drm_i915_gem_object *obj,
> >                             const struct i915_ggtt_view *view);
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c 
> > b/drivers/gpu/drm/i915/i915_gem.c
> > index b7d66aa..db90043 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -3098,25 +3098,26 @@ out:
> >   static int
> >   __i915_gem_object_sync(struct drm_i915_gem_object *obj,
> >                  struct intel_engine_cs *to,
> > -               struct drm_i915_gem_request *req)
> > +               struct drm_i915_gem_request *from_req,
> > +               struct drm_i915_gem_request **to_req)
> >   {
> >       struct intel_engine_cs *from;
> >       int ret;
> >
> > -    from = i915_gem_request_get_ring(req);
> > +    from = i915_gem_request_get_ring(from_req);
> >       if (to == from)
> >           return 0;
> >
> > -    if (i915_gem_request_completed(req, true))
> > +    if (i915_gem_request_completed(from_req, true))
> >           return 0;
> >
> > -    ret = i915_gem_check_olr(req);
> > +    ret = i915_gem_check_olr(from_req);
> >       if (ret)
> >           return ret;
> >
> >       if (!i915_semaphore_is_enabled(obj->base.dev)) {
> >           struct drm_i915_private *i915 = to_i915(obj->base.dev);
> > -        ret = __i915_wait_request(req,
> > +        ret = __i915_wait_request(from_req,
> > atomic_read(&i915->gpu_error.reset_counter),
> >                         i915->mm.interruptible,
> >                         NULL,
> > @@ -3124,15 +3125,25 @@ __i915_gem_object_sync(struct 
> > drm_i915_gem_object *obj,
> >           if (ret)
> >               return ret;
> >
> > -        i915_gem_object_retire_request(obj, req);
> > +        i915_gem_object_retire_request(obj, from_req);
> >       } else {
> >           int idx = intel_ring_sync_index(from, to);
> > -        u32 seqno = i915_gem_request_get_seqno(req);
> > +        u32 seqno = i915_gem_request_get_seqno(from_req);
> >
> > +        WARN_ON(!to_req);
> > +
> > +        /* Optimization: Avoid semaphore sync when we are sure we 
> > already
> > +         * waited for an object with higher seqno */
>
> 2. How about using the standard multi-line comment format?

Not my comment. It looks like Chris removed it in his re-write of the 
sync code and I accidentally put it back in when resolving the merge 
conflicts. I'll drop it again.

> /* (empty line)
>  * (first line)
>  * (second line)
>  */
>
> >           if (seqno <= from->semaphore.sync_seqno[idx])
> >               return 0;
> >
> > -        trace_i915_gem_ring_sync_to(from, to, req);
> > +        if (*to_req == NULL) {
> > +            ret = i915_gem_request_alloc(to, to->default_context, 
> > to_req);
> > +            if (ret)
> > +                return ret;
> > +        }
> > +
> > +        trace_i915_gem_ring_sync_to(from, to, from_req);
> >           ret = to->semaphore.sync_to(to, from, seqno);
> >           if (ret)
> >               return ret;
> > @@ -3153,6 +3164,9 @@ __i915_gem_object_sync(struct 
> > drm_i915_gem_object *obj,
> >    *
> >    * @obj: object which may be in use on another ring.
> >    * @to: ring we wish to use the object on. May be NULL.
> > + * @to_req: request we wish to use the object for. See below.
> > + *          This will be allocated and returned if a request is
> > + *          required but not passed in.
> >    *
> >    * This code is meant to abstract object synchronization with the GPU.
> >    * Calling with NULL implies synchronizing the object with the CPU
> > @@ -3168,11 +3182,22 @@ __i915_gem_object_sync(struct 
> > drm_i915_gem_object *obj,
> >    * - If we are a write request (pending_write_domain is set), the new
> >    *   request must wait for outstanding read requests to complete.
> >    *
> > + * For CPU synchronisation (NULL to) no request is required. For 
> > syncing with
> > + * rings to_req must be non-NULL. However, a request does not have 
> > to be
> > + * pre-allocated. If *to_req is null and sync commands will be 
> > emitted then a
> > + * request will be allocated automatically and returned through 
> > *to_req. Note
> > + * that it is not guaranteed that commands will be emitted (because the
> > + * might already be idle). Hence there is no need to create a 
> > request that
> > + * might never have any work submitted. Note further that if a 
> > request is
> > + * returned in *to_req, it is the responsibility of the caller to 
> > submit
> > + * that request (after potentially adding more work to it).
> > + *
>
> 3. "(because the might already be idle)" : The what? The engine?
> 4. "NULL" and "null" mixed. Please be consistent.
>
> Overall, the explanation is better than in the last patch version
>
> With those minor changes:
>
> Reviewed-by: Tomas Elf <tomas.elf@xxxxxxxxx>
>
> Thanks,
> Tomas
>
> >    * Returns 0 if successful, else propagates up the lower layer error.
> >    */
> >   int
> >   i915_gem_object_sync(struct drm_i915_gem_object *obj,
> > -             struct intel_engine_cs *to)
> > +             struct intel_engine_cs *to,
> > +             struct drm_i915_gem_request **to_req)
> >   {
> >       const bool readonly = obj->base.pending_write_domain == 0;
> >       struct drm_i915_gem_request *req[I915_NUM_RINGS];
> > @@ -3194,7 +3219,7 @@ i915_gem_object_sync(struct drm_i915_gem_object 
> > *obj,
> >                   req[n++] = obj->last_read_req[i];
> >       }
> >       for (i = 0; i < n; i++) {
> > -        ret = __i915_gem_object_sync(obj, to, req[i]);
> > +        ret = __i915_gem_object_sync(obj, to, req[i], to_req);
> >           if (ret)
> >               return ret;
> >       }
> > @@ -4144,12 +4169,13 @@ int
> >   i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
> >                        u32 alignment,
> >                        struct intel_engine_cs *pipelined,
> > +                     struct drm_i915_gem_request **pipelined_request,
> >                        const struct i915_ggtt_view *view)
> >   {
> >       u32 old_read_domains, old_write_domain;
> >       int ret;
> >
> > -    ret = i915_gem_object_sync(obj, pipelined);
> > +    ret = i915_gem_object_sync(obj, pipelined, pipelined_request);
> >       if (ret)
> >           return ret;
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c 
> > b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > index 50b1ced..bea92ad 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > @@ -899,7 +899,7 @@ i915_gem_execbuffer_move_to_gpu(struct 
> > drm_i915_gem_request *req,
> >           struct drm_i915_gem_object *obj = vma->obj;
> >
> >           if (obj->active & other_rings) {
> > -            ret = i915_gem_object_sync(obj, req->ring);
> > +            ret = i915_gem_object_sync(obj, req->ring, &req);
> >               if (ret)
> >                   return ret;
> >           }
> > diff --git a/drivers/gpu/drm/i915/intel_display.c 
> > b/drivers/gpu/drm/i915/intel_display.c
> > index 657a333..6528ada 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -2338,7 +2338,8 @@ int
> >   intel_pin_and_fence_fb_obj(struct drm_plane *plane,
> >                  struct drm_framebuffer *fb,
> >                  const struct drm_plane_state *plane_state,
> > -               struct intel_engine_cs *pipelined)
> > +               struct intel_engine_cs *pipelined,
> > +               struct drm_i915_gem_request **pipelined_request)
> >   {
> >       struct drm_device *dev = fb->dev;
> >       struct drm_i915_private *dev_priv = dev->dev_private;
> > @@ -2403,7 +2404,7 @@ intel_pin_and_fence_fb_obj(struct drm_plane 
> > *plane,
> >
> >       dev_priv->mm.interruptible = false;
> >       ret = i915_gem_object_pin_to_display_plane(obj, alignment, 
> > pipelined,
> > -                           &view);
> > +                           pipelined_request, &view);
> >       if (ret)
> >           goto err_interruptible;
> >
> > @@ -11119,6 +11120,7 @@ static int intel_crtc_page_flip(struct 
> > drm_crtc *crtc,
> >       struct intel_unpin_work *work;
> >       struct intel_engine_cs *ring;
> >       bool mmio_flip;
> > +    struct drm_i915_gem_request *request = NULL;
> >       int ret;
> >
> >       /*
> > @@ -11225,7 +11227,7 @@ static int intel_crtc_page_flip(struct 
> > drm_crtc *crtc,
> >        */
> >       ret = intel_pin_and_fence_fb_obj(crtc->primary, fb,
> >                        crtc->primary->state,
> > -                     mmio_flip ? 
> > i915_gem_request_get_ring(obj->last_write_req) : ring);
> > +                     mmio_flip ? 
> > i915_gem_request_get_ring(obj->last_write_req) : ring, &request);
> >       if (ret)
> >           goto cleanup_pending;
> >
> > @@ -11256,6 +11258,9 @@ static int intel_crtc_page_flip(struct 
> > drm_crtc *crtc,
> >                       intel_ring_get_request(ring));
> >       }
> >
> > +    if (request)
> > +        i915_add_request_no_flush(request->ring);
> > +
> >       work->flip_queued_vblank = drm_crtc_vblank_count(crtc);
> >       work->enable_stall_check = true;
> >
> > @@ -11273,6 +11278,8 @@ static int intel_crtc_page_flip(struct 
> > drm_crtc *crtc,
> >   cleanup_unpin:
> >       intel_unpin_fb_obj(fb, crtc->primary->state);
> >   cleanup_pending:
> > +    if (request)
> > +        i915_gem_request_cancel(request);
> >       atomic_dec(&intel_crtc->unpin_work_count);
> >       mutex_unlock(&dev->struct_mutex);
> >   cleanup:
> > @@ -13171,7 +13178,7 @@ intel_prepare_plane_fb(struct drm_plane *plane,
> >           if (ret)
> >               DRM_DEBUG_KMS("failed to attach phys object\n");
> >       } else {
> > -        ret = intel_pin_and_fence_fb_obj(plane, fb, new_state, NULL);
> > +        ret = intel_pin_and_fence_fb_obj(plane, fb, new_state, NULL, 
> > NULL);
> >       }
> >
> >       if (ret == 0)
> > @@ -15218,7 +15225,7 @@ void intel_modeset_gem_init(struct drm_device 
> > *dev)
> >           ret = intel_pin_and_fence_fb_obj(c->primary,
> >                            c->primary->fb,
> >                            c->primary->state,
> > -                         NULL);
> > +                         NULL, NULL);
> >           mutex_unlock(&dev->struct_mutex);
> >           if (ret) {
> >               DRM_ERROR("failed to pin boot fb on pipe %d\n",
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h 
> > b/drivers/gpu/drm/i915/intel_drv.h
> > index 02d8317..73650ae 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -1034,7 +1034,8 @@ void intel_release_load_detect_pipe(struct 
> > drm_connector *connector,
> >   int intel_pin_and_fence_fb_obj(struct drm_plane *plane,
> >                      struct drm_framebuffer *fb,
> >                      const struct drm_plane_state *plane_state,
> > -                   struct intel_engine_cs *pipelined);
> > +                   struct intel_engine_cs *pipelined,
> > +                   struct drm_i915_gem_request **pipelined_request);
> >   struct drm_framebuffer *
> >   __intel_framebuffer_create(struct drm_device *dev,
> >                  struct drm_mode_fb_cmd2 *mode_cmd,
> > diff --git a/drivers/gpu/drm/i915/intel_fbdev.c 
> > b/drivers/gpu/drm/i915/intel_fbdev.c
> > index 4e7e7da..dd9f3b2 100644
> > --- a/drivers/gpu/drm/i915/intel_fbdev.c
> > +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> > @@ -151,7 +151,7 @@ static int intelfb_alloc(struct drm_fb_helper 
> > *helper,
> >       }
> >
> >       /* Flush everything out, we'll be doing GTT only from now on */
> > -    ret = intel_pin_and_fence_fb_obj(NULL, fb, NULL, NULL);
> > +    ret = intel_pin_and_fence_fb_obj(NULL, fb, NULL, NULL, NULL);
> >       if (ret) {
> >           DRM_ERROR("failed to pin obj: %d\n", ret);
> >           goto out_fb;
> > diff --git a/drivers/gpu/drm/i915/intel_lrc.c 
> > b/drivers/gpu/drm/i915/intel_lrc.c
> > index 6d005b1..f8e8fdb 100644
> > --- a/drivers/gpu/drm/i915/intel_lrc.c
> > +++ b/drivers/gpu/drm/i915/intel_lrc.c
> > @@ -638,7 +638,7 @@ static int execlists_move_to_gpu(struct 
> > drm_i915_gem_request *req,
> >           struct drm_i915_gem_object *obj = vma->obj;
> >
> >           if (obj->active & other_rings) {
> > -            ret = i915_gem_object_sync(obj, req->ring);
> > +            ret = i915_gem_object_sync(obj, req->ring, &req);
> >               if (ret)
> >                   return ret;
> >           }
> > diff --git a/drivers/gpu/drm/i915/intel_overlay.c 
> > b/drivers/gpu/drm/i915/intel_overlay.c
> > index e7534b9..0f8187a 100644
> > --- a/drivers/gpu/drm/i915/intel_overlay.c
> > +++ b/drivers/gpu/drm/i915/intel_overlay.c
> > @@ -724,7 +724,7 @@ static int intel_overlay_do_put_image(struct 
> > intel_overlay *overlay,
> >       if (ret != 0)
> >           return ret;
> >
> > -    ret = i915_gem_object_pin_to_display_plane(new_bo, 0, NULL,
> > +    ret = i915_gem_object_pin_to_display_plane(new_bo, 0, NULL, NULL,
> >                              &i915_ggtt_view_normal);
> >       if (ret != 0)
> >           return ret;

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