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drm: Initialize struct drm_crtc_state.no_vblank from device settings

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[ 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: 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
Stable-dep-of: 13fcfcb2a9a4 ("drm/msm/mdp5: Add check for kzalloc")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Thomas Zimmermann 2020-01-29 13:05:17 +01:00 committed by Greg Kroah-Hartman
parent 9b2f584490
commit 2a8bb9dce7
5 changed files with 70 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
drivers/gpu/drm/drm_atomic_helper.c
View File

@ -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.

28
drivers/gpu/drm/drm_vblank.c
View File

@ -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 @@ 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

34
include/drm/drm_crtc.h
View File

@ -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

7
include/drm/drm_simple_kms_helper.h
View File

@ -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);

1
include/drm/drm_vblank.h
View File

@ -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);