| Message ID | 20200801184929.2eaxyoq6fm3nk4ey@smtp.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/vkms: guarantee vblank when capturing crc | expand |
On Sat, Aug 01, 2020 at 03:49:29PM -0300, Melissa Wen wrote: > VKMS needs vblank interrupts enabled to capture CRC. When vblank is > disabled, tests like kms_cursor_crc and kms_pipe_crc_basic getting stuck > waiting for a capture that will not occur until vkms wakes up. This > patch ensures that vblank remains enabled as long as the CRC capture is > needed. > > It clears the execution of the following kms_cursor_crc subtests: > 1. pipe-A-cursor-[size,alpha-opaque, NxN-(on-screen, off-screen, sliding, > random, fast-moving])] - successful when running individually. > 2. pipe-A-cursor-dpms passes again > 3. pipe-A-cursor-suspend also passes > > The issue was initially tracked in the sequential execution of IGT > kms_cursor_crc subtest: when running the test sequence or one of its > subtests twice, the odd execs complete and the pairs get stuck in an > endless wait. In the IGT code, calling a wait_for_vblank on preparing > for CRC capture prevented the busy-wait. But the problem persisted in > the pipe-A-cursor-dpms and -suspend subtests. > > Checking the history, the pipe-A-cursor-dpms subtest was successful > when, in vkms_atomic_commit_tail, instead of using the flip_done op, it > used wait_for_vblanks. Another way to prevent blocking was > wait_one_vblank when enabling crtc. However, in both cases, > pipe-A-cursor-suspend persisted blocking in the 2nd start of CRC > capture, which may indicate that something got stuck in the step of CRC > setup. Indeed, wait_one_vblank in the crc setup was able to sync things > and free all kms_cursor_crc subtests. > > Besides, other alternatives to force enabling vblanks or prevent > disabling them such as calling drm_crtc_put_vblank or modeset_enables > before commit_planes + offdelay = 0, also unlock all subtests > executions. These facts together converge on the lack of vblank to > unblock the crc capture. > > Finally, considering the vkms's dependence on vblank interruptions to > perform tasks, this patch acquires a vblank ref when setup CRC source > and releases ref when disabling crc capture, ensuring vblanks happen to > compute CRC. > > Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com> > Cc: Haneen Mohammed <hamohammed.sa@gmail.com> > Co-developed-by: Sidong Yang <realwakka@gmail.com> > Signed-off-by: Sidong Yang <realwakka@gmail.com> > Co-developed-by: Daniel Vetter <daniel@ffwll.ch> > Signed-off-by: Daniel Vetter <daniel@ffwll.ch> > Signed-off-by: Melissa Wen <melissa.srw@gmail.com> Excellent summary of the debug story. > --- > drivers/gpu/drm/vkms/vkms_composer.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c > index 4af2f19480f4..1161eaa383f1 100644 > --- a/drivers/gpu/drm/vkms/vkms_composer.c > +++ b/drivers/gpu/drm/vkms/vkms_composer.c > @@ -241,6 +241,14 @@ int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name) > > ret = vkms_crc_parse_source(src_name, &enabled); > > + /* Ensure that vblank interruptions are enabled for crc capture */ > + /* Enabling CRC: acquire vblank ref */ This comment just explains what the code does, that's not needed. The first comment I think can be replaced if we create a little helper function like void vkms_set_composer(struct vkms_output, bool enable) { bool old_state; if (enabled) drm_crtc_vblank_get(crtc); spin_lock_irq(&out->lock); old_enable = out->composer_enabled; out->composer_enabled = enabled; spin_unlock_irq(&out->lock); if (old_enabled) drm_crtc_vblank_put(crtc); } This should also help as prep for the writeback work, where we have a 2nd user that might need to enable the composer (maybe even need to switch to refcounting the composer state then). > + if (enabled) > + drm_crtc_vblank_get(crtc); > + /* Disabling CRC: release vblank ref */ > + if (!src_name) > + drm_crtc_vblank_put(crtc); I'm not sure this correctly releases the vblank reference in all cases, I think the suggestion in the helper function pseudo code should work better. It does mean we temporarily elevate the vblank refcount if we go enabled -> enabled, but that's not a problem since it's refcounted. Cheers, Daniel > + > spin_lock_irq(&out->lock); > out->composer_enabled = enabled; > spin_unlock_irq(&out->lock); > -- > 2.27.0 >
On 08/04, daniel@ffwll.ch wrote: > On Sat, Aug 01, 2020 at 03:49:29PM -0300, Melissa Wen wrote: > > VKMS needs vblank interrupts enabled to capture CRC. When vblank is > > disabled, tests like kms_cursor_crc and kms_pipe_crc_basic getting stuck > > waiting for a capture that will not occur until vkms wakes up. This > > patch ensures that vblank remains enabled as long as the CRC capture is > > needed. > > > > It clears the execution of the following kms_cursor_crc subtests: > > 1. pipe-A-cursor-[size,alpha-opaque, NxN-(on-screen, off-screen, sliding, > > random, fast-moving])] - successful when running individually. > > 2. pipe-A-cursor-dpms passes again > > 3. pipe-A-cursor-suspend also passes > > > > The issue was initially tracked in the sequential execution of IGT > > kms_cursor_crc subtest: when running the test sequence or one of its > > subtests twice, the odd execs complete and the pairs get stuck in an > > endless wait. In the IGT code, calling a wait_for_vblank on preparing > > for CRC capture prevented the busy-wait. But the problem persisted in > > the pipe-A-cursor-dpms and -suspend subtests. > > > > Checking the history, the pipe-A-cursor-dpms subtest was successful > > when, in vkms_atomic_commit_tail, instead of using the flip_done op, it > > used wait_for_vblanks. Another way to prevent blocking was > > wait_one_vblank when enabling crtc. However, in both cases, > > pipe-A-cursor-suspend persisted blocking in the 2nd start of CRC > > capture, which may indicate that something got stuck in the step of CRC > > setup. Indeed, wait_one_vblank in the crc setup was able to sync things > > and free all kms_cursor_crc subtests. > > > > Besides, other alternatives to force enabling vblanks or prevent > > disabling them such as calling drm_crtc_put_vblank or modeset_enables > > before commit_planes + offdelay = 0, also unlock all subtests > > executions. These facts together converge on the lack of vblank to > > unblock the crc capture. > > > > Finally, considering the vkms's dependence on vblank interruptions to > > perform tasks, this patch acquires a vblank ref when setup CRC source > > and releases ref when disabling crc capture, ensuring vblanks happen to > > compute CRC. > > > > Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com> > > Cc: Haneen Mohammed <hamohammed.sa@gmail.com> > > Co-developed-by: Sidong Yang <realwakka@gmail.com> > > Signed-off-by: Sidong Yang <realwakka@gmail.com> > > Co-developed-by: Daniel Vetter <daniel@ffwll.ch> > > Signed-off-by: Daniel Vetter <daniel@ffwll.ch> > > Signed-off-by: Melissa Wen <melissa.srw@gmail.com> > > Excellent summary of the debug story. > > > --- > > drivers/gpu/drm/vkms/vkms_composer.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c > > index 4af2f19480f4..1161eaa383f1 100644 > > --- a/drivers/gpu/drm/vkms/vkms_composer.c > > +++ b/drivers/gpu/drm/vkms/vkms_composer.c > > @@ -241,6 +241,14 @@ int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name) > > > > ret = vkms_crc_parse_source(src_name, &enabled); > > > > + /* Ensure that vblank interruptions are enabled for crc capture */ > > + /* Enabling CRC: acquire vblank ref */ > > This comment just explains what the code does, that's not needed. The > first comment I think can be replaced if we create a little helper > function like > > void vkms_set_composer(struct vkms_output, bool enable) { > bool old_state; > > if (enabled) > drm_crtc_vblank_get(crtc); > > spin_lock_irq(&out->lock); > old_enable = out->composer_enabled; > out->composer_enabled = enabled; > spin_unlock_irq(&out->lock); > > if (old_enabled) > drm_crtc_vblank_put(crtc); > > } > > This should also help as prep for the writeback work, where we have a 2nd > user that might need to enable the composer (maybe even need to switch to > refcounting the composer state then). > Hi Daniel, Thanks for the feedback and advice. I applied the suggestion and just sent a v2. Best regards, Melissa > > + if (enabled) > > + drm_crtc_vblank_get(crtc); > > + /* Disabling CRC: release vblank ref */ > > + if (!src_name) > > + drm_crtc_vblank_put(crtc); > > I'm not sure this correctly releases the vblank reference in all cases, I > think the suggestion in the helper function pseudo code should work > better. It does mean we temporarily elevate the vblank refcount if we go > enabled -> enabled, but that's not a problem since it's refcounted. > > Cheers, Daniel > > > + > > spin_lock_irq(&out->lock); > > out->composer_enabled = enabled; > > spin_unlock_irq(&out->lock); > > -- > > 2.27.0 > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch
diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c index 4af2f19480f4..1161eaa383f1 100644 --- a/drivers/gpu/drm/vkms/vkms_composer.c +++ b/drivers/gpu/drm/vkms/vkms_composer.c @@ -241,6 +241,14 @@ int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name) ret = vkms_crc_parse_source(src_name, &enabled); + /* Ensure that vblank interruptions are enabled for crc capture */ + /* Enabling CRC: acquire vblank ref */ + if (enabled) + drm_crtc_vblank_get(crtc); + /* Disabling CRC: release vblank ref */ + if (!src_name) + drm_crtc_vblank_put(crtc); + spin_lock_irq(&out->lock); out->composer_enabled = enabled; spin_unlock_irq(&out->lock);