Attachment 143480 Details for Bug 109749 – backported for 5.0 patch

[patch] backported for 5.0 patch

0002-drm-amd-display-Use-vrr-friendly-pageflip-throttling.patch (text/plain), 5.91 KB, created by bmilreu on 2019-02-26 21:39:11 UTC

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Creator: bmilreu

Created: 2019-02-26 21:39:11 UTC

Size: 5.91 KB

patch

obsolete

>From c1005e42807449b6800cdbae356fd2f19b0edc58 Mon Sep 17 00:00:00 2001
>From: Mario Kleiner <mario.kleiner.de@gmail.com>
>Date: Wed, 30 Jan 2019 06:04:46 +0100
>Subject: [PATCH 2/9] drm/amd/display: Use vrr friendly pageflip throttling in
> DC.
>MIME-Version: 1.0
>Content-Type: text/plain; charset=UTF-8
>Content-Transfer-Encoding: 8bit
>
>In VRR mode, keep track of the vblank count of the last
>completed pageflip in amdgpu_crtc->last_flip_vblank, as
>recorded in the pageflip completion handler after each
>completed flip.
>
>Use that count to prevent mmio programming a new pageflip
>within the same vblank in which the last pageflip completed,
>iow. to throttle pageflips to at most one flip per video
>frame, while at the same time allowing to request a flip
>not only before start of vblank, but also anywhere within
>vblank.
>
>The old logic did the same, and made sense for regular fixed
>refresh rate flipping, but in vrr mode it prevents requesting
>a flip anywhere inside the possibly huge vblank, thereby
>reducing framerate in vrr mode instead of improving it, by
>delaying a slightly delayed flip requests up to a maximum
>vblank duration + 1 scanout duration. This would limit VRR
>usefulness to only help applications with a very high GPU
>demand, which can submit the flip request before start of
>vblank, but then have to wait long for fences to complete.
>
>With this method a flip can be both requested and - after
>fences have completed - executed, ie. it doesn't matter if
>the request (amdgpu_dm_do_flip()) gets delayed until deep
>into the extended vblank due to cpu execution delays. This
>also allows clients which want to regulate framerate within
>the vrr range a much more fine-grained control of flip timing,
>a feature that might be useful for video playback, and is
>very useful for neuroscience/vision research applications.
>
>In regular non-VRR mode, retain the old flip submission
>behavior. This to keep flip scheduling for fullscreen X11/GLX
>OpenGL clients intact, if they use the GLX_OML_sync_control
>extensions glXSwapBufferMscOML(, ..., target_msc,...) function
>with a specific target_msc target vblank count.
>
>glXSwapBuffersMscOML() or DRI3/Present PresentPixmap() will
>not flip at the proper target_msc for a non-zero target_msc
>if VRR mode is active with this patch. They'd often flip one
>frame too early. However, this limitation should not matter
>much in VRR mode, as scheduling based on vblank counts is
>pretty futile/unusable under variable refresh duration
>anyway, so no real extra harm is done.
>
>Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
>Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
>Cc: Harry Wentland <harry.wentland@amd.com>
>Cc: Alex Deucher <alexander.deucher@amd.com>
>Cc: Michel DÃ¤nzer <michel@daenzer.net>
>---
> drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h      |  1 +
> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 27 ++++++++++++++++---
> 2 files changed, 24 insertions(+), 4 deletions(-)
>
>diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
>index aadd0fa42e43..3aa42c64484a 100644
>--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
>+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_mode.h
>@@ -405,6 +405,7 @@ struct amdgpu_crtc {
> 	struct amdgpu_flip_work *pflip_works;
> 	enum amdgpu_flip_status pflip_status;
> 	int deferred_flip_completion;
>+	u64 last_flip_vblank;
> 	/* pll sharing */
> 	struct amdgpu_atom_ss ss;
> 	bool ss_enabled;
>diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>index b90ca9da74b1..6c24a4eaaf39 100644
>--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>@@ -303,12 +303,11 @@ static void dm_pflip_high_irq(void *interrupt_params)
> 		return;
> 	}
> 
>+	/* Update to correct count(s) if racing with vblank irq */
>+	amdgpu_crtc->last_flip_vblank = drm_crtc_accurate_vblank_count(&amdgpu_crtc->base);
> 
> 	/* wake up userspace */
> 	if (amdgpu_crtc->event) {
>-		/* Update to correct count(s) if racing with vblank irq */
>-		drm_crtc_accurate_vblank_count(&amdgpu_crtc->base);
>-
> 		drm_crtc_send_vblank_event(&amdgpu_crtc->base, amdgpu_crtc->event);
> 
> 		/* page flip completed. clean up */
>@@ -4826,6 +4825,8 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
> 			to_dm_crtc_state(drm_atomic_get_old_crtc_state(state, pcrtc));
> 	int planes_count = 0;
> 	unsigned long flags;
>+	u64 last_flip_vblank;
>+	bool vrr_active = acrtc_state->freesync_config.state == VRR_STATE_ACTIVE_VARIABLE;
> 
> 	/* update planes when needed */
> 	for_each_oldnew_plane_in_state(state, plane, old_plane_state, new_plane_state, i) {
>@@ -4857,6 +4858,16 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
> 			/* In commit tail framework this cannot happen */
> 			WARN_ON(1);
> 		}
>+
>+		/* For variable refresh rate mode only:
>+		 * Get vblank of last completed flip to avoid > 1 vrr flips per
>+		 * video frame by use of throttling, but allow flip programming
>+		 * anywhere in the possibly large variable vrr vblank interval
>+		 * for fine-grained flip timing control and more opportunity to
>+		 * avoid stutter on late submission of amdgpu_dm_do_flip() calls.
>+		 */
>+		last_flip_vblank = acrtc_attach->last_flip_vblank;
>+
> 		spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
> 
> 		if (!pflip_needed || plane->type == DRM_PLANE_TYPE_OVERLAY) {
>@@ -4880,10 +4891,18 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
> 			if (plane->type == DRM_PLANE_TYPE_PRIMARY)
> 				drm_crtc_vblank_get(crtc);
> 
>+			/* Use old throttling in non-vrr fixed refresh rate mode
>+			 * to keep flip scheduling based on target vblank counts
>+			 * working in a backwards compatible way, e.g., clients
>+			 * using GLX_OML_sync_control extension.
>+			 */
>+			if (!vrr_active)
>+				last_flip_vblank = drm_crtc_vblank_count(crtc);
>+
> 			amdgpu_dm_do_flip(
> 				crtc,
> 				fb,
>-				(uint32_t)drm_crtc_vblank_count(crtc) + *wait_for_vblank,
>+				(uint32_t) last_flip_vblank + *wait_for_vblank,
> 				dc_state);
> 		}
> 
>-- 
>2.17.1
>

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