From def35e7c592616bc09be328de8795e5e624a3cf8 Mon Sep 17 00:00:00 2001 From: Shayenne Moura Date: Wed, 30 Jan 2019 14:06:36 -0200 Subject: drm/vkms: Bugfix extra vblank frame 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 --- drivers/gpu/drm/vkms/vkms_crtc.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'drivers/gpu/drm/vkms/vkms_crtc.c') diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c index d44bfc392491..23146ff2a25b 100644 --- a/drivers/gpu/drm/vkms/vkms_crtc.c +++ b/drivers/gpu/drm/vkms/vkms_crtc.c @@ -87,6 +87,9 @@ 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; } -- cgit From ba420afab565bdc7b028ddd4f222260f2de7a1db Mon Sep 17 00:00:00 2001 From: Shayenne Moura Date: Wed, 30 Jan 2019 14:07:11 -0200 Subject: drm/vkms: Bugfix racing hrtimer vblank handle When the vblank irq happens, kernel time subsystem executes `vkms_vblank_simulate`. In parallel or not, it prepares all stuff necessary to the next vblank with arm, and it must flush these stuff before the next vblank irq. However, vblank counter is ahead when arm is executed in parallel with handle vblank. CPU 0: CPU 1: | | atomic_commit_tail is ongoing | | | | hrtimer: vkms_vblank_simulate() | | | drm_crtc_handle_vblank() | | drm_crtc_arm_vblank() | | | ->get_vblank_timestamp() | | | | hrtimer_forward_now() Then, we should guarantee that the vblank interval time is correct (not changed) before finish the vblank handle. Fix the bug including the call to `hrtimer_forward_now()` in the same lock of `drm_crtc_handle_vblank()` to ensure that the timestamp update is correct when finish the vblank handle. 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/e2e4b8f3a5cab7b2dba75bf1930f86b0a4ee08c9.1548856186.git.shayenneluzmoura@gmail.com --- drivers/gpu/drm/vkms/vkms_crtc.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) (limited to 'drivers/gpu/drm/vkms/vkms_crtc.c') diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c index 23146ff2a25b..5a095610726b 100644 --- a/drivers/gpu/drm/vkms/vkms_crtc.c +++ b/drivers/gpu/drm/vkms/vkms_crtc.c @@ -10,13 +10,17 @@ #include #include -static void _vblank_handle(struct vkms_output *output) +static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer) { + struct vkms_output *output = container_of(timer, struct vkms_output, + vblank_hrtimer); struct drm_crtc *crtc = &output->crtc; struct vkms_crtc_state *state = to_vkms_crtc_state(crtc->state); + int ret_overrun; bool ret; spin_lock(&output->lock); + ret = drm_crtc_handle_vblank(crtc); if (!ret) DRM_ERROR("vkms failure on handling vblank"); @@ -37,19 +41,9 @@ static void _vblank_handle(struct vkms_output *output) DRM_WARN("failed to queue vkms_crc_work_handle"); } - spin_unlock(&output->lock); -} - -static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer) -{ - struct vkms_output *output = container_of(timer, struct vkms_output, - vblank_hrtimer); - int ret_overrun; - - _vblank_handle(output); - ret_overrun = hrtimer_forward_now(&output->vblank_hrtimer, output->period_ns); + spin_unlock(&output->lock); return HRTIMER_RESTART; } -- cgit From 09ef09b4ab95dc405ad4171ec2cd8a4ff5227108 Mon Sep 17 00:00:00 2001 From: Shayenne Moura Date: Wed, 6 Feb 2019 18:08:13 -0200 Subject: drm/vkms: WARN when hrtimer_forward_now fails Add a warn to verify the hrtimer_forward_now return and changes ret_overrun from int to u64 to match the return value provided by hrtimer_forward_now. Signed-off-by: Shayenne Moura Signed-off-by: Rodrigo Siqueira Link: https://patchwork.freedesktop.org/patch/msgid/20190206200813.d5w7gjpepoeeadiy@smtp.gmail.com --- drivers/gpu/drm/vkms/vkms_crtc.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'drivers/gpu/drm/vkms/vkms_crtc.c') diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c index 5a095610726b..734a3e197df8 100644 --- a/drivers/gpu/drm/vkms/vkms_crtc.c +++ b/drivers/gpu/drm/vkms/vkms_crtc.c @@ -16,7 +16,7 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer) vblank_hrtimer); struct drm_crtc *crtc = &output->crtc; struct vkms_crtc_state *state = to_vkms_crtc_state(crtc->state); - int ret_overrun; + u64 ret_overrun; bool ret; spin_lock(&output->lock); @@ -43,6 +43,8 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer) ret_overrun = hrtimer_forward_now(&output->vblank_hrtimer, output->period_ns); + WARN_ON(ret_overrun != 1); + spin_unlock(&output->lock); return HRTIMER_RESTART; -- cgit