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author | Thomas Zimmermann <tzimmermann@suse.de> | 2020-01-29 13:05:17 +0100 |
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committer | Thomas Zimmermann <tzimmermann@suse.de> | 2020-01-30 08:57:12 +0100 |
commit | 7beb691f1e6f349c9df3384a85e7a53c5601aaaf (patch) | |
tree | e36f1fff3b1c02f362a5efee6a0416b63e14b707 /include/drm/drm_crtc.h | |
parent | drm/auth: Drop master_create/destroy hooks (diff) | |
download | linux-7beb691f1e6f349c9df3384a85e7a53c5601aaaf.tar.xz linux-7beb691f1e6f349c9df3384a85e7a53c5601aaaf.zip |
drm: Initialize struct drm_crtc_state.no_vblank from device settings
At the end of a commit, atomic helpers can generate a fake VBLANK event
automatically. Originally implemented for writeback connectors, the
functionality can be used by any driver and/or hardware without proper
VBLANK interrupt.
The patch updates the documentation to make this behaviour official:
settings struct drm_crtc_state.no_vblank to true enables automatic
generation of fake VBLANK events.
The new interface drm_dev_has_vblank() returns true if vblanking has
been initialized for a device, or false otherwise. Atomic helpers use
this function when initializing no_vblank in the CRTC state in
drm_atomic_helper_check_modeset(). If vblanking has been initialized
for a device, no_blank is disabled. Otherwise it's enabled. Hence,
atomic helpers will automatically send out fake VBLANK events with any
driver that did not initialize vblanking.
v5:
* more precise documentation and commit message
v4:
* replace drm_crtc_has_vblank() with drm_dev_has_vblank()
* add drm_dev_has_vblank() in this patch
* move driver changes into separate patches
v3:
* squash all related changes patches into this patch
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200129120531.6891-2-tzimmermann@suse.de
Diffstat (limited to 'include/drm/drm_crtc.h')
-rw-r--r-- | include/drm/drm_crtc.h | 34 |
1 files changed, 27 insertions, 7 deletions
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h index 5e9b15a0e8c5..6bef2f41d4d7 100644 --- a/include/drm/drm_crtc.h +++ b/include/drm/drm_crtc.h @@ -174,12 +174,25 @@ struct drm_crtc_state { * @no_vblank: * * Reflects the ability of a CRTC to send VBLANK events. This state - * usually depends on the pipeline configuration, and the main usuage - * is CRTCs feeding a writeback connector operating in oneshot mode. - * In this case the VBLANK event is only generated when a job is queued - * to the writeback connector, and we want the core to fake VBLANK - * events when this part of the pipeline hasn't changed but others had - * or when the CRTC and connectors are being disabled. + * usually depends on the pipeline configuration. If set to true, DRM + * atomic helpers will send out a fake VBLANK event during display + * updates after all hardware changes have been committed. This is + * implemented in drm_atomic_helper_fake_vblank(). + * + * One usage is for drivers and/or hardware without support for VBLANK + * interrupts. Such drivers typically do not initialize vblanking + * (i.e., call drm_vblank_init() with the number of CRTCs). For CRTCs + * without initialized vblanking, this field is set to true in + * drm_atomic_helper_check_modeset(), and a fake VBLANK event will be + * send out on each update of the display pipeline by + * drm_atomic_helper_fake_vblank(). + * + * Another usage is CRTCs feeding a writeback connector operating in + * oneshot mode. In this case the fake VBLANK event is only generated + * when a job is queued to the writeback connector, and we want the + * core to fake VBLANK events when this part of the pipeline hasn't + * changed but others had or when the CRTC and connectors are being + * disabled. * * __drm_atomic_helper_crtc_duplicate_state() will not reset the value * from the current state, the CRTC driver is then responsible for @@ -335,7 +348,14 @@ struct drm_crtc_state { * - Events for disabled CRTCs are not allowed, and drivers can ignore * that case. * - * This can be handled by the drm_crtc_send_vblank_event() function, + * For very simple hardware without VBLANK interrupt, enabling + * &struct drm_crtc_state.no_vblank makes DRM's atomic commit helpers + * send a fake VBLANK event at the end of the display update after all + * hardware changes have been applied. See + * drm_atomic_helper_fake_vblank(). + * + * For more complex hardware this + * can be handled by the drm_crtc_send_vblank_event() function, * which the driver should call on the provided event upon completion of * the atomic commit. Note that if the driver supports vblank signalling * and timestamping the vblank counters and timestamps must agree with |