Quoting Chris Wilson (2017-08-17 13:37:06)
> If we miss the current vblank because the gpu was busy, that may cause a
> jitter as the frame rate temporarily drops. We try to limit the impact
> of this by then boosting the GPU clock to deliver the frame as quickly
> as possible. Originally done in commit 6ad790c0f5ac ("drm/i915: Boost GPU
> frequency if we detect outstanding pageflips") but was never forward
> ported to atomic and finally dropped in commit fd3a40242e87 ("drm/i915:
> Rip out legacy page_flip completion/irq handling").
>
> References: https://bugs.freedesktop.org/show_bug.cgi?id=102199
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Either of you like to ack the return of this code to the display
subsystem? It's still reactionary and will one day be replace by a pony,
or perhaps supplemented by one.
-Chris
> ---
> drivers/gpu/drm/i915/intel_display.c | 59 ++++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/i915/intel_drv.h | 1 -
> drivers/gpu/drm/i915/intel_pm.c | 42 ++-----------------------
> 3 files changed, 62 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 0e93ec201fe3..7d5b19553637 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -12636,6 +12636,55 @@ static const struct drm_crtc_funcs intel_crtc_funcs = {
> .set_crc_source = intel_crtc_set_crc_source,
> };
>
> +struct wait_rps_boost {
> + struct wait_queue_entry wait;
> +
> + struct drm_crtc *crtc;
> + struct drm_i915_gem_request *request;
> +};
> +
> +static int do_rps_boost(struct wait_queue_entry *_wait,
> + unsigned mode, int sync, void *key)
> +{
> + struct wait_rps_boost *wait = container_of(_wait, typeof(*wait), wait);
> + struct drm_i915_gem_request *rq = wait->request;
> +
> + gen6_rps_boost(rq, NULL);
> + i915_gem_request_put(rq);
> +
> + drm_crtc_vblank_put(wait->crtc);
> +
> + list_del(&wait->wait.entry);
> + kfree(wait);
> + return 1;
> +}
> +
> +static void add_rps_boost_after_vblank(struct drm_crtc *crtc,
> + struct dma_fence *fence)
> +{
> + struct wait_rps_boost *wait;
> +
> + if (!dma_fence_is_i915(fence))
> + return;
> +
> + if (drm_crtc_vblank_get(crtc))
> + return;
> +
> + wait = kmalloc(sizeof(*wait), GFP_KERNEL);
> + if (!wait) {
> + drm_crtc_vblank_put(crtc);
> + return;
> + }
> +
> + wait->request = to_request(dma_fence_get(fence));
> + wait->crtc = crtc;
> +
> + wait->wait.func = do_rps_boost;
> + wait->wait.flags = 0;
> +
> + add_wait_queue(drm_crtc_vblank_waitqueue(crtc), &wait->wait);
> +}
> +
> /**
> * intel_prepare_plane_fb - Prepare fb for usage on plane
> * @plane: drm plane to prepare for
> @@ -12733,12 +12782,22 @@ intel_prepare_plane_fb(struct drm_plane *plane,
> return ret;
>
> if (!new_state->fence) { /* implicit fencing */
> + struct dma_fence *fence;
> +
> ret = i915_sw_fence_await_reservation(&intel_state->commit_ready,
> obj->resv, NULL,
> false, I915_FENCE_TIMEOUT,
> GFP_KERNEL);
> if (ret < 0)
> return ret;
> +
> + fence = reservation_object_get_excl_rcu(obj->resv);
> + if (fence) {
> + add_rps_boost_after_vblank(new_state->crtc, fence);
> + dma_fence_put(fence);
> + }
> + } else {
> + add_rps_boost_after_vblank(new_state->crtc, new_state->fence);
> }
>
> return 0;
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index fa47285918f4..e092354b4d63 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1844,7 +1844,6 @@ void gen6_rps_reset_ei(struct drm_i915_private *dev_priv);
> void gen6_rps_idle(struct drm_i915_private *dev_priv);
> void gen6_rps_boost(struct drm_i915_gem_request *rq,
> struct intel_rps_client *rps);
> -void intel_queue_rps_boost_for_request(struct drm_i915_gem_request *req);
> void g4x_wm_get_hw_state(struct drm_device *dev);
> void vlv_wm_get_hw_state(struct drm_device *dev);
> void ilk_wm_get_hw_state(struct drm_device *dev);
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index ed662937ec3c..c9fa2eb1903c 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -6169,6 +6169,7 @@ void gen6_rps_boost(struct drm_i915_gem_request *rq,
> struct intel_rps_client *rps)
> {
> struct drm_i915_private *i915 = rq->i915;
> + unsigned long flags;
> bool boost;
>
> /* This is intentionally racy! We peek at the state here, then
> @@ -6178,13 +6179,13 @@ void gen6_rps_boost(struct drm_i915_gem_request *rq,
> return;
>
> boost = false;
> - spin_lock_irq(&rq->lock);
> + spin_lock_irqsave(&rq->lock, flags);
> if (!rq->waitboost && !i915_gem_request_completed(rq)) {
> atomic_inc(&i915->rps.num_waiters);
> rq->waitboost = true;
> boost = true;
> }
> - spin_unlock_irq(&rq->lock);
> + spin_unlock_irqrestore(&rq->lock, flags);
> if (!boost)
> return;
>
> @@ -9132,43 +9133,6 @@ int intel_freq_opcode(struct drm_i915_private *dev_priv, int val)
> return DIV_ROUND_CLOSEST(val, GT_FREQUENCY_MULTIPLIER);
> }
>
> -struct request_boost {
> - struct work_struct work;
> - struct drm_i915_gem_request *req;
> -};
> -
> -static void __intel_rps_boost_work(struct work_struct *work)
> -{
> - struct request_boost *boost = container_of(work, struct request_boost, work);
> - struct drm_i915_gem_request *req = boost->req;
> -
> - if (!i915_gem_request_completed(req))
> - gen6_rps_boost(req, NULL);
> -
> - i915_gem_request_put(req);
> - kfree(boost);
> -}
> -
> -void intel_queue_rps_boost_for_request(struct drm_i915_gem_request *req)
> -{
> - struct request_boost *boost;
> -
> - if (req == NULL || INTEL_GEN(req->i915) < 6)
> - return;
> -
> - if (i915_gem_request_completed(req))
> - return;
> -
> - boost = kmalloc(sizeof(*boost), GFP_ATOMIC);
> - if (boost == NULL)
> - return;
> -
> - boost->req = i915_gem_request_get(req);
> -
> - INIT_WORK(&boost->work, __intel_rps_boost_work);
> - queue_work(req->i915->wq, &boost->work);
> -}
> -
> void intel_pm_setup(struct drm_i915_private *dev_priv)
> {
> mutex_init(&dev_priv->rps.hw_lock);
> --
> 2.14.1
>
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