[PATCH 2/2] drm/amd/display: Block immediate flips for non-fast updates

[Francis, David]

Series is:

Reviewed-by: David Francis <david.francis at amd.com>

________________________________
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
Sent: August 2, 2019 11:11:50 AM
To: amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
Cc: Li, Sun peng (Leo) <Sunpeng.Li at amd.com>; Francis, David <David.Francis at amd.com>; Lakha, Bhawanpreet <Bhawanpreet.Lakha at amd.com>; Kazlauskas, Nicholas <Nicholas.Kazlauskas at amd.com>
Subject: [PATCH 2/2] drm/amd/display: Block immediate flips for non-fast updates

[Why]
Underflow can occur in the case where we change buffer pitch, DCC state,
rotation or mirroring for a plane while also performing an immediate
flip. It can also generate a p-state warning stack trace on DCN1 which
is typically observed during the cursor handler pipe locking because of
how frequent cursor updates can occur.

[How]
Store the update type on each CRTC - every plane will have access to
the CRTC state if it's flipping. If the update type is not
UPDATE_TYPE_FAST then the immediate flip should be disallowed.

No changes to the target vblank sequencing need to be done, we just
need to ensure that the surface registers do a double buffered update.

Cc: David Francis <david.francis at amd.com>
Cc: Bhawanpreet Lakha <bhawanpreet.lakha at amd.com>
Cc: Leo Li <sunpeng.li at amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c    | 16 +++++++++++++++-
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h    |  1 +
 2 files changed, 16 insertions(+), 1 deletion(-)

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 ffb3c7247ac6..e941d0d3794b 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -5690,8 +5690,14 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
                 bundle->surface_updates[planes_count].plane_info =
                         &bundle->plane_infos[planes_count];

+               /*
+                * Only allow immediate flips for fast updates that don't
+                * change FB pitch, DCC state, rotation or mirroing.
+                */
                 bundle->flip_addrs[planes_count].flip_immediate =
-                               (crtc->state->pageflip_flags & DRM_MODE_PAGE_FLIP_ASYNC) != 0;
+                       (crtc->state->pageflip_flags &
+                        DRM_MODE_PAGE_FLIP_ASYNC) != 0 &&
+                       acrtc_state->update_type == UPDATE_TYPE_FAST;

                 timestamp_ns = ktime_get_ns();
                 bundle->flip_addrs[planes_count].flip_timestamp_in_us = div_u64(timestamp_ns, 1000);
@@ -7311,6 +7317,14 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
                 state->async_update = !drm_atomic_helper_async_check(dev, state);
         }

+       /* Store the overall update type for use later in atomic check. */
+       for_each_new_crtc_in_state (state, crtc, new_crtc_state, i) {
+               struct dm_crtc_state *dm_new_crtc_state =
+                       to_dm_crtc_state(new_crtc_state);
+
+               dm_new_crtc_state->update_type = (int)overall_update_type;
+       }
+
         /* Must be success */
         WARN_ON(ret);
         return ret;
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index da48a857949f..cbd6608f58e6 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -307,6 +307,7 @@ struct dm_crtc_state {
         bool cm_has_degamma;
         bool cm_is_degamma_srgb;

+       int update_type;
         int active_planes;
         bool interrupts_enabled;

--
2.17.1

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