xref: /linux/drivers/gpu/drm/drm_vblank_helper.c (revision 24f171c7e145f43b9f187578e89b0982ce87e54c)

// SPDX-License-Identifier: MIT

#include <drm/drm_atomic.h>
#include <drm/drm_crtc.h>
#include <drm/drm_managed.h>
#include <drm/drm_modeset_helper_vtables.h>
#include <drm/drm_print.h>
#include <drm/drm_vblank.h>
#include <drm/drm_vblank_helper.h>

/**
 * DOC: overview
 *
 * The vblank helper library provides functions for supporting vertical
 * blanking in DRM drivers.
 *
 * For vblank timers, several callback implementations are available.
 * Drivers enable support for vblank timers by setting the vblank callbacks
 * in struct &drm_crtc_funcs to the helpers provided by this library. The
 * initializer macro DRM_CRTC_VBLANK_TIMER_FUNCS does this conveniently.
 * The driver further has to send the VBLANK event from its atomic_flush
 * callback and control vblank from the CRTC's atomic_enable and atomic_disable
 * callbacks. The callbacks are located in struct &drm_crtc_helper_funcs.
 * The vblank helper library provides implementations of these callbacks
 * for drivers without further requirements. The initializer macro
 * DRM_CRTC_HELPER_VBLANK_FUNCS sets them coveniently.
 *
 * Once the driver enables vblank support with drm_vblank_init(), each
 * CRTC's vblank timer fires according to the programmed display mode. By
 * default, the vblank timer invokes drm_crtc_handle_vblank(). Drivers with
 * more specific requirements can set their own handler function in
 * struct &drm_crtc_helper_funcs.handle_vblank_timeout.
 */

/*
 * VBLANK helpers
 */

/**
 * drm_crtc_vblank_atomic_flush -
 *	Implements struct &drm_crtc_helper_funcs.atomic_flush
 * @crtc: The CRTC
 * @state: The atomic state to apply
 *
 * The helper drm_crtc_vblank_atomic_flush() implements atomic_flush of
 * struct drm_crtc_helper_funcs for CRTCs that only need to send out a
 * VBLANK event.
 *
 * See also struct &drm_crtc_helper_funcs.atomic_flush.
 */
void drm_crtc_vblank_atomic_flush(struct drm_crtc *crtc,
				  struct drm_atomic_state *state)
{
	struct drm_device *dev = crtc->dev;
	struct drm_crtc_state *crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
	struct drm_pending_vblank_event *event;

	spin_lock_irq(&dev->event_lock);

	event = crtc_state->event;
	crtc_state->event = NULL;

	if (event) {
		if (drm_crtc_vblank_get(crtc) == 0)
			drm_crtc_arm_vblank_event(crtc, event);
		else
			drm_crtc_send_vblank_event(crtc, event);
	}

	spin_unlock_irq(&dev->event_lock);
}
EXPORT_SYMBOL(drm_crtc_vblank_atomic_flush);

/**
 * drm_crtc_vblank_atomic_enable - Implements struct &drm_crtc_helper_funcs.atomic_enable
 * @crtc: The CRTC
 * @state: The atomic state
 *
 * The helper drm_crtc_vblank_atomic_enable() implements atomic_enable
 * of struct drm_crtc_helper_funcs for CRTCs the only need to enable VBLANKs.
 *
 * See also struct &drm_crtc_helper_funcs.atomic_enable.
 */
void drm_crtc_vblank_atomic_enable(struct drm_crtc *crtc,
				   struct drm_atomic_state *state)
{
	drm_crtc_vblank_on(crtc);
}
EXPORT_SYMBOL(drm_crtc_vblank_atomic_enable);

/**
 * drm_crtc_vblank_atomic_disable - Implements struct &drm_crtc_helper_funcs.atomic_disable
 * @crtc: The CRTC
 * @state: The atomic state
 *
 * The helper drm_crtc_vblank_atomic_disable() implements atomic_disable
 * of struct drm_crtc_helper_funcs for CRTCs the only need to disable VBLANKs.
 *
 * See also struct &drm_crtc_funcs.atomic_disable.
 */
void drm_crtc_vblank_atomic_disable(struct drm_crtc *crtc,
				    struct drm_atomic_state *state)
{
	drm_crtc_vblank_off(crtc);
}
EXPORT_SYMBOL(drm_crtc_vblank_atomic_disable);

/*
 * VBLANK timer
 */

/**
 * drm_crtc_vblank_helper_enable_vblank_timer - Implements struct &drm_crtc_funcs.enable_vblank
 * @crtc: The CRTC
 *
 * The helper drm_crtc_vblank_helper_enable_vblank_timer() implements
 * enable_vblank of struct drm_crtc_helper_funcs for CRTCs that require
 * a VBLANK timer. It sets up the timer on the first invocation. The
 * started timer expires after the current frame duration. See struct
 * &drm_vblank_crtc.framedur_ns.
 *
 * See also struct &drm_crtc_helper_funcs.enable_vblank.
 *
 * Returns:
 * 0 on success, or a negative errno code otherwise.
 */
int drm_crtc_vblank_helper_enable_vblank_timer(struct drm_crtc *crtc)
{
	return drm_crtc_vblank_start_timer(crtc);
}
EXPORT_SYMBOL(drm_crtc_vblank_helper_enable_vblank_timer);

/**
 * drm_crtc_vblank_helper_disable_vblank_timer - Implements struct &drm_crtc_funcs.disable_vblank
 * @crtc: The CRTC
 *
 * The helper drm_crtc_vblank_helper_disable_vblank_timer() implements
 * disable_vblank of struct drm_crtc_funcs for CRTCs that require a
 * VBLANK timer.
 *
 * See also struct &drm_crtc_helper_funcs.disable_vblank.
 */
void drm_crtc_vblank_helper_disable_vblank_timer(struct drm_crtc *crtc)
{
	drm_crtc_vblank_cancel_timer(crtc);
}
EXPORT_SYMBOL(drm_crtc_vblank_helper_disable_vblank_timer);

/**
 * drm_crtc_vblank_helper_get_vblank_timestamp_from_timer -
 *	Implements struct &drm_crtc_funcs.get_vblank_timestamp
 * @crtc: The CRTC
 * @max_error: Maximum acceptable error
 * @vblank_time: Returns the next vblank timestamp
 * @in_vblank_irq: True is called from drm_crtc_handle_vblank()
 *
 * The helper drm_crtc_helper_get_vblank_timestamp_from_timer() implements
 * get_vblank_timestamp of struct drm_crtc_funcs for CRTCs that require a
 * VBLANK timer. It returns the timestamp according to the timer's expiry
 * time.
 *
 * See also struct &drm_crtc_funcs.get_vblank_timestamp.
 *
 * Returns:
 * True on success, or false otherwise.
 */
bool drm_crtc_vblank_helper_get_vblank_timestamp_from_timer(struct drm_crtc *crtc,
							    int *max_error,
							    ktime_t *vblank_time,
							    bool in_vblank_irq)
{
	drm_crtc_vblank_get_vblank_timeout(crtc, vblank_time);

	return true;
}
EXPORT_SYMBOL(drm_crtc_vblank_helper_get_vblank_timestamp_from_timer);