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| author | Thomas Zimmermann <tzimmermann@suse.de> | 2020-01-29 13:05:17 +0100 |
|---|---|---|
| committer | Thomas Zimmermann <tzimmermann@suse.de> | 2020-01-30 08:57:12 +0100 |
| commit | 7beb691f1e6f349c9df3384a85e7a53c5601aaaf (patch) | |
| tree | e36f1fff3b1c02f362a5efee6a0416b63e14b707 /drivers/gpu/drm/drm_vblank.c | |
| parent | 86a9360be144c9c981c48f8e5b2214179cb53dc5 (diff) | |
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 'drivers/gpu/drm/drm_vblank.c')
| -rw-r--r-- | drivers/gpu/drm/drm_vblank.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 1659b13b178c..27a99c486f02 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -69,6 +69,12 @@ * &drm_driver.max_vblank_count. In that case the vblank core only disables the * vblanks after a timer has expired, which can be configured through the * ``vblankoffdelay`` module parameter. + * + * Drivers for hardware without support for vertical-blanking interrupts + * must not call drm_vblank_init(). For such drivers, atomic helpers will + * automatically generate fake vblank events as part of the display update. + * This functionality also can be controlled by the driver by enabling and + * disabling struct drm_crtc_state.no_vblank. */ /* Retry timestamp calculation up to 3 times to satisfy @@ -502,6 +508,28 @@ err: EXPORT_SYMBOL(drm_vblank_init); /** + * drm_dev_has_vblank - test if vblanking has been initialized for + * a device + * @dev: the device + * + * Drivers may call this function to test if vblank support is + * initialized for a device. For most hardware this means that vblanking + * can also be enabled. + * + * Atomic helpers use this function to initialize + * &drm_crtc_state.no_vblank. See also drm_atomic_helper_check_modeset(). + * + * Returns: + * True if vblanking has been initialized for the given device, false + * otherwise. + */ +bool drm_dev_has_vblank(const struct drm_device *dev) +{ + return dev->num_crtcs != 0; +} +EXPORT_SYMBOL(drm_dev_has_vblank); + +/** * drm_crtc_vblank_waitqueue - get vblank waitqueue for the CRTC * @crtc: which CRTC's vblank waitqueue to retrieve * |