[PATCH] drm/vkms: modify sequence disable/plane/enable in commit_tail

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Sidong Yang

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Jul 29, 2020, 11:22:49 AM7/29/20
to Rodrigo Siqueira, Haneen Mohammed, Daniel Vetter, David Airlie, Sidong Yang, linux-...@vger.kernel.org, dri-...@lists.freedesktop.org, kerne...@googlegroups.com
This patch modifies function call sequence in commit tail. This is for
the problem that raised when kms_cursor_crc test is tested repeatedly.
In second test, there is an bug that crtc commit doesn't start vblank events.
Because there is some error about vblank's refcount. in commit_flush() that
called from commit_plane, drm_vblank_get() is called and vblank is enabled
in normal case. But in second test, vblank isn't enable for vblank->refcount
is already increased in previous test. Increased refcount will be decreased
in drm_atomic_helper_commit_modeset_enables() after commit_plane.
Therefore, commit_plane should be called after commit_modeset_enable.

In this situation, there is a warning raised in get_vblank_timestamp().
hrtimer.node.expires and vblank->time are zero for no vblank events before.
This patch returns current time when vblank is not enabled.

Cc: Daniel Vetter <dan...@ffwll.ch>
Cc: Rodrigo Siqueira <rodrigosi...@gmail.com>
Cc: Haneen Mohammed <hamoha...@gmail.com>

Signed-off-by: Sidong Yang <real...@gmail.com>
---
drivers/gpu/drm/vkms/vkms_crtc.c | 5 +++++
drivers/gpu/drm/vkms/vkms_drv.c | 4 ++--
2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
index ac85e17428f8..09c012d54d58 100644
--- a/drivers/gpu/drm/vkms/vkms_crtc.c
+++ b/drivers/gpu/drm/vkms/vkms_crtc.c
@@ -86,6 +86,11 @@ static bool vkms_get_vblank_timestamp(struct drm_crtc *crtc,
struct vkms_output *output = &vkmsdev->output;
struct drm_vblank_crtc *vblank = &dev->vblank[pipe];

+ if (!READ_ONCE(vblank->enabled)) {
+ *vblank_time = ktime_get();
+ return true;
+ }
+
*vblank_time = READ_ONCE(output->vblank_hrtimer.node.expires);

if (WARN_ON(*vblank_time == vblank->time))
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
index 1e8b2169d834..c2c83a01d4a7 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.c
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -76,10 +76,10 @@ static void vkms_atomic_commit_tail(struct drm_atomic_state *old_state)

drm_atomic_helper_commit_modeset_disables(dev, old_state);

- drm_atomic_helper_commit_planes(dev, old_state, 0);
-
drm_atomic_helper_commit_modeset_enables(dev, old_state);

+ drm_atomic_helper_commit_planes(dev, old_state, 0);
+
drm_atomic_helper_fake_vblank(old_state);

drm_atomic_helper_commit_hw_done(old_state);
--
2.17.1

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