From b5c1dc9d8fa4d52153ddc10375e977905fca2c98 Mon Sep 17 00:00:00 2001 From: Shayenne Moura Date: Wed, 30 Jan 2019 14:06:36 -0200 Subject: [PATCH] drm/vkms: Bugfix extra vblank frame [ Upstream commit def35e7c592616bc09be328de8795e5e624a3cf8 ] kms_flip tests are breaking on vkms when simulate vblank because vblank event sequence count returns one extra frame after arm vblank event to make a page flip. When vblank interrupt happens, userspace processes the vblank event and issues the next page flip command. Kernel calls queue_work to call commit_planes and arm the new page flip. The next vblank picks up the newly armed vblank event and vblank interrupt happens again. The arm and vblank event are asynchronous, then, on the next vblank, we receive x+2 from `get_vblank_timestamp`, instead x+1, although timestamp and vblank seqno matches. Function `get_vblank_timestamp` is reached by 2 ways: - from `drm_mode_page_flip_ioctl`: driver is doing one atomic operation to synchronize planes in the same output. There is no vblank simulation, the `drm_crtc_arm_vblank_event` function adds 1 on vblank count, and the variable in_vblank_irq is false - from `vkms_vblank_simulate`: since the driver is doing a vblank simulation, the variable in_vblank_irq is true. Fix this problem subtracting one vblank period from vblank_time when `get_vblank_timestamp` is called from trace `drm_mode_page_flip_ioctl`, i.e., is not a real vblank interrupt, and getting the timestamp and vblank seqno when it is a real vblank interrupt. The reason for all this is that get_vblank_timestamp always supplies the timestamp for the next vblank event. The hrtimer is the vblank simulator, and it needs the correct previous value to present the next vblank. Since this is how hw timestamp registers work and what the vblank core expects. Signed-off-by: Shayenne Moura Signed-off-by: Daniel Vetter Reviewed-by: Rodrigo Siqueira Signed-off-by: Rodrigo Siqueira Link: https://patchwork.freedesktop.org/patch/msgid/171e6e1c239cbca0c3df7183ed8acdfeeace9cf4.1548856186.git.shayenneluzmoura@gmail.com Signed-off-by: Sasha Levin --- drivers/gpu/drm/vkms/vkms_crtc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c index 1ea2dd35bca9..0a271f762a0a 100644 --- a/drivers/gpu/drm/vkms/vkms_crtc.c +++ b/drivers/gpu/drm/vkms/vkms_crtc.c @@ -55,6 +55,9 @@ bool vkms_get_vblank_timestamp(struct drm_device *dev, unsigned int pipe, *vblank_time = output->vblank_hrtimer.node.expires; + if (!in_vblank_irq) + *vblank_time -= output->period_ns; + return true; } -- GitLab