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Commit 2a8bb9dc authored by Thomas Zimmermann's avatar Thomas Zimmermann Committed by Greg Kroah-Hartman
Browse files

drm: Initialize struct drm_crtc_state.no_vblank from device settings 



[ Upstream commit 7beb691f1e6f349c9df3384a85e7a53c5601aaaf ]

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: default avatarThomas Zimmermann <tzimmermann@suse.de>
Acked-by: default avatarGerd Hoffmann <kraxel@redhat.com>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200129120531.6891-2-tzimmermann@suse.de


Stable-dep-of: 13fcfcb2a9a4 ("drm/msm/mdp5: Add check for kzalloc")
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 9b2f5844

drivers/gpu/drm/drm_atomic_helper.c

+9 −1
Original line number Diff line number Diff line
@@ -589,6 +589,7 @@ mode_valid(struct drm_atomic_state *state) 
 * &drm_crtc_state.connectors_changed is set when a connector is added or

 * removed from the crtc.  &drm_crtc_state.active_changed is set when

 * &drm_crtc_state.active changes, which is used for DPMS.

 * &drm_crtc_state.no_vblank is set from the result of drm_dev_has_vblank().

 * See also: drm_atomic_crtc_needs_modeset()

 *

 * IMPORTANT:
@@ -655,6 +656,11 @@ drm_atomic_helper_check_modeset(struct drm_device *dev, 


			return -EINVAL;

		}



		if (drm_dev_has_vblank(dev))

			new_crtc_state->no_vblank = false;

		else

			new_crtc_state->no_vblank = true;

	}



	ret = handle_conflicting_encoders(state, false);
@@ -2205,7 +2211,9 @@ EXPORT_SYMBOL(drm_atomic_helper_wait_for_dependencies); 
 * when a job is queued, and any change to the pipeline that does not touch the

 * connector is leading to timeouts when calling

 * drm_atomic_helper_wait_for_vblanks() or

 * drm_atomic_helper_wait_for_flip_done().

 * drm_atomic_helper_wait_for_flip_done(). In addition to writeback

 * connectors, this function can also fake VBLANK events for CRTCs without

 * VBLANK interrupt.

 *

 * This is part of the atomic helper support for nonblocking commits, see

 * drm_atomic_helper_setup_commit() for an overview.

drivers/gpu/drm/drm_vblank.c

+28 −0
Original line number Diff line number Diff line
@@ -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
@@ -488,6 +494,28 @@ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs) 
}

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

include/drm/drm_crtc.h

+27 −7
Original line number Diff line number Diff line
@@ -175,12 +175,25 @@ 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
@@ -336,7 +349,14 @@ 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

include/drm/drm_simple_kms_helper.h

+5 −2
Original line number Diff line number Diff line
@@ -100,8 +100,11 @@ struct drm_simple_display_pipe_funcs { 
	 * This is the function drivers should submit the

	 * &drm_pending_vblank_event from. Using either

	 * drm_crtc_arm_vblank_event(), when the driver supports vblank

	 * interrupt handling, or drm_crtc_send_vblank_event() directly in case

	 * the hardware lacks vblank support entirely.

	 * interrupt handling, or drm_crtc_send_vblank_event() for more

	 * complex case. In case the hardware lacks vblank support entirely,

	 * drivers can set &struct drm_crtc_state.no_vblank in

	 * &struct drm_simple_display_pipe_funcs.check and let DRM's

	 * atomic helper fake a vblank event.

	 */

	void (*update)(struct drm_simple_display_pipe *pipe,

		       struct drm_plane_state *old_plane_state);

include/drm/drm_vblank.h

+1 −0
Original line number Diff line number Diff line
@@ -195,6 +195,7 @@ struct drm_vblank_crtc { 
};



int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs);

bool drm_dev_has_vblank(const struct drm_device *dev);

u64 drm_crtc_vblank_count(struct drm_crtc *crtc);

u64 drm_crtc_vblank_count_and_time(struct drm_crtc *crtc,

				   ktime_t *vblanktime);