linux-kernel - [PATCH] drm/amd/display: fix flickering caused by S/G mode

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Date:   Fri, 14 Apr 2023 15:33:30 -0400
From:   Hamza Mahfooz <hamza.mahfooz@....com>
To:     <amd-gfx@...ts.freedesktop.org>
CC:     Hamza Mahfooz <hamza.mahfooz@....com>, <stable@...r.kernel.org>,
        "Harry Wentland" <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        "Rodrigo Siqueira" <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        Qingqing Zhuo <qingqing.zhuo@....com>,
        "Hans de Goede" <hdegoede@...hat.com>,
        Hersen Wu <hersenxs.wu@....com>,
        Stylon Wang <stylon.wang@....com>,
        Luben Tuikov <luben.tuikov@....com>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] drm/amd/display: fix flickering caused by S/G mode

Currently, we allow the framebuffer for a given plane to move between
memory domains, however when that happens it causes the screen to
flicker, it is even possible for the framebuffer to change memory
domains on every plane update (causing a continuous flicker effect). So,
to fix this, don't perform an immediate flip in the aforementioned case.

Cc: stable@...r.kernel.org
Fixes: 81d0bcf99009 ("drm/amdgpu: make display pinning more flexible (v2)")
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@....com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 41 ++++++++++++++++++-
 1 file changed, 39 insertions(+), 2 deletions(-)

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 da3045fdcb6d..9a4e7408384a 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -7897,6 +7897,34 @@ static void amdgpu_dm_commit_cursors(struct drm_atomic_state *state)
 			amdgpu_dm_plane_handle_cursor_update(plane, old_plane_state);
 }
 
+static inline uint32_t get_mem_type(struct amdgpu_device *adev,
+				    struct drm_gem_object *obj,
+				    bool check_domain)
+{
+	struct amdgpu_bo *abo = gem_to_amdgpu_bo(obj);
+	uint32_t mem_type;
+
+	if (unlikely(amdgpu_bo_reserve(abo, true)))
+		return 0;
+
+	if (unlikely(dma_resv_reserve_fences(abo->tbo.base.resv, 1)))
+		goto err;
+
+	if (check_domain &&
+	    amdgpu_display_supported_domains(adev, abo->flags) !=
+	    (AMDGPU_GEM_DOMAIN_VRAM | AMDGPU_GEM_DOMAIN_GTT))
+		goto err;
+
+	mem_type = abo->tbo.resource->mem_type;
+	amdgpu_bo_unreserve(abo);
+
+	return mem_type;
+
+err:
+	amdgpu_bo_unreserve(abo);
+	return 0;
+}
+
 static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
 				    struct dc_state *dc_state,
 				    struct drm_device *dev,
@@ -7916,6 +7944,7 @@ 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, vpos, hpos;
 	unsigned long flags;
+	uint32_t mem_type;
 	u32 target_vblank, last_flip_vblank;
 	bool vrr_active = amdgpu_dm_crtc_vrr_active(acrtc_state);
 	bool cursor_update = false;
@@ -8035,13 +8064,21 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
 			}
 		}
 
+		mem_type = get_mem_type(dm->adev, old_plane_state->fb->obj[0],
+					true);
+
 		/*
 		 * Only allow immediate flips for fast updates that don't
-		 * change FB pitch, DCC state, rotation or mirroing.
+		 * change memory domain, FB pitch, DCC state, rotation or
+		 * mirroring.
 		 */
 		bundle->flip_addrs[planes_count].flip_immediate =
 			crtc->state->async_flip &&
-			acrtc_state->update_type == UPDATE_TYPE_FAST;
+			acrtc_state->update_type == UPDATE_TYPE_FAST &&
+			(!mem_type || (mem_type && get_mem_type(dm->adev,
+								fb->obj[0],
+								false) ==
+				       mem_type));
 
 		timestamp_ns = ktime_get_ns();
 		bundle->flip_addrs[planes_count].flip_timestamp_in_us = div_u64(timestamp_ns, 1000);
-- 
2.40.0