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authorThomas Zimmermann <tzimmermann@suse.de>2020-01-29 15:05:17 +0300
committerThomas Zimmermann <tzimmermann@suse.de>2020-01-30 10:57:12 +0300
commit7beb691f1e6f349c9df3384a85e7a53c5601aaaf (patch)
treee36f1fff3b1c02f362a5efee6a0416b63e14b707 /drivers/gpu/drm/drm_vblank.c
parent86a9360be144c9c981c48f8e5b2214179cb53dc5 (diff)
downloadlinux-7beb691f1e6f349c9df3384a85e7a53c5601aaaf.tar.xz
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.c28
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
*