[mirror_ubuntu-artful-kernel.git] / drivers / gpu / drm / i915 / intel_frontbuffer.c

/*
 * Copyright © 2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 * Authors:
 *	Daniel Vetter <daniel.vetter@ffwll.ch>
 */

/**
 * DOC: frontbuffer tracking
 *
 * Many features require us to track changes to the currently active
 * frontbuffer, especially rendering targeted at the frontbuffer.
 *
 * To be able to do so GEM tracks frontbuffers using a bitmask for all possible
 * frontbuffer slots through i915_gem_track_fb(). The function in this file are
 * then called when the contents of the frontbuffer are invalidated, when
 * frontbuffer rendering has stopped again to flush out all the changes and when
 * the frontbuffer is exchanged with a flip. Subsystems interested in
 * frontbuffer changes (e.g. PSR, FBC, DRRS) should directly put their callbacks
 * into the relevant places and filter for the frontbuffer slots that they are
 * interested int.
 *
 * On a high level there are two types of powersaving features. The first one
 * work like a special cache (FBC and PSR) and are interested when they should
 * stop caching and when to restart caching. This is done by placing callbacks
 * into the invalidate and the flush functions: At invalidate the caching must
 * be stopped and at flush time it can be restarted. And maybe they need to know
 * when the frontbuffer changes (e.g. when the hw doesn't initiate an invalidate
 * and flush on its own) which can be achieved with placing callbacks into the
 * flip functions.
 *
 * The other type of display power saving feature only cares about busyness
 * (e.g. DRRS). In that case all three (invalidate, flush and flip) indicate
 * busyness. There is no direct way to detect idleness. Instead an idle timer
 * work delayed work should be started from the flush and flip functions and
 * cancelled as soon as busyness is detected.
 *
 * Note that there's also an older frontbuffer activity tracking scheme which
 * just tracks general activity. This is done by the various mark_busy and
 * mark_idle functions. For display power management features using these
 * functions is deprecated and should be avoided.
 */

#include <drm/drmP.h>

#include "intel_drv.h"
#include "i915_drv.h"

static void intel_increase_pllclock(struct drm_device *dev,
				    enum pipe pipe)
{
	struct drm_i915_private *dev_priv = dev->dev_private;
	int dpll_reg = DPLL(pipe);
	int dpll;

	if (!HAS_GMCH_DISPLAY(dev))
		return;

	if (!dev_priv->lvds_downclock_avail)
		return;

	dpll = I915_READ(dpll_reg);
	if (!HAS_PIPE_CXSR(dev) && (dpll & DISPLAY_RATE_SELECT_FPA1)) {
		DRM_DEBUG_DRIVER("upclocking LVDS\n");

		assert_panel_unlocked(dev_priv, pipe);

		dpll &= ~DISPLAY_RATE_SELECT_FPA1;
		I915_WRITE(dpll_reg, dpll);
		intel_wait_for_vblank(dev, pipe);

		dpll = I915_READ(dpll_reg);
		if (dpll & DISPLAY_RATE_SELECT_FPA1)
			DRM_DEBUG_DRIVER("failed to upclock LVDS!\n");
	}
}

/**
 * intel_mark_fb_busy - mark given planes as busy
 * @dev: DRM device
 * @frontbuffer_bits: bits for the affected planes
 *
 * This function gets called every time the screen contents change. It can be
 * used to keep e.g. the update rate at the nominal refresh rate with DRRS.
 */
static void intel_mark_fb_busy(struct drm_device *dev,
			       unsigned frontbuffer_bits)
{
	struct drm_i915_private *dev_priv = dev->dev_private;
	enum pipe pipe;

	for_each_pipe(dev_priv, pipe) {
		if (!(frontbuffer_bits & INTEL_FRONTBUFFER_ALL_MASK(pipe)))
			continue;

		intel_increase_pllclock(dev, pipe);
	}
}

/**
 * intel_fb_obj_invalidate - invalidate frontbuffer object
 * @obj: GEM object to invalidate
 * @origin: which operation caused the invalidation
 *
 * This function gets called every time rendering on the given object starts and
 * frontbuffer caching (fbc, low refresh rate for DRRS, panel self refresh) must
 * be invalidated. For ORIGIN_CS any subsequent invalidation will be delayed
 * until the rendering completes or a flip on this frontbuffer plane is
 * scheduled.
 */
void intel_fb_obj_invalidate(struct drm_i915_gem_object *obj,
			     enum fb_op_origin origin)
{
	struct drm_device *dev = obj->base.dev;
	struct drm_i915_private *dev_priv = dev->dev_private;

	WARN_ON(!mutex_is_locked(&dev->struct_mutex));

	if (!obj->frontbuffer_bits)
		return;

	if (origin == ORIGIN_CS) {
		mutex_lock(&dev_priv->fb_tracking.lock);
		dev_priv->fb_tracking.busy_bits
			|= obj->frontbuffer_bits;
		dev_priv->fb_tracking.flip_bits
			&= ~obj->frontbuffer_bits;
		mutex_unlock(&dev_priv->fb_tracking.lock);
	}

	intel_mark_fb_busy(dev, obj->frontbuffer_bits);

	intel_psr_invalidate(dev, obj->frontbuffer_bits);
	intel_edp_drrs_invalidate(dev, obj->frontbuffer_bits);
	intel_fbc_invalidate(dev_priv, obj->frontbuffer_bits, origin);
}

/**
 * intel_frontbuffer_flush - flush frontbuffer
 * @dev: DRM device
 * @frontbuffer_bits: frontbuffer plane tracking bits
 *
 * This function gets called every time rendering on the given planes has
 * completed and frontbuffer caching can be started again. Flushes will get
 * delayed if they're blocked by some outstanding asynchronous rendering.
 *
 * Can be called without any locks held.
 */
void intel_frontbuffer_flush(struct drm_device *dev,
			     unsigned frontbuffer_bits)
{
	struct drm_i915_private *dev_priv = dev->dev_private;

	/* Delay flushing when rings are still busy.*/
	mutex_lock(&dev_priv->fb_tracking.lock);
	frontbuffer_bits &= ~dev_priv->fb_tracking.busy_bits;
	mutex_unlock(&dev_priv->fb_tracking.lock);

	intel_mark_fb_busy(dev, frontbuffer_bits);

	intel_edp_drrs_flush(dev, frontbuffer_bits);
	intel_psr_flush(dev, frontbuffer_bits);
	intel_fbc_flush(dev_priv, frontbuffer_bits);
}

/**
 * intel_fb_obj_flush - flush frontbuffer object
 * @obj: GEM object to flush
 * @retire: set when retiring asynchronous rendering
 *
 * This function gets called every time rendering on the given object has
 * completed and frontbuffer caching can be started again. If @retire is true
 * then any delayed flushes will be unblocked.
 */
void intel_fb_obj_flush(struct drm_i915_gem_object *obj,
			bool retire)
{
	struct drm_device *dev = obj->base.dev;
	struct drm_i915_private *dev_priv = dev->dev_private;
	unsigned frontbuffer_bits;

	WARN_ON(!mutex_is_locked(&dev->struct_mutex));

	if (!obj->frontbuffer_bits)
		return;

	frontbuffer_bits = obj->frontbuffer_bits;

	if (retire) {
		mutex_lock(&dev_priv->fb_tracking.lock);
		/* Filter out new bits since rendering started. */
		frontbuffer_bits &= dev_priv->fb_tracking.busy_bits;

		dev_priv->fb_tracking.busy_bits &= ~frontbuffer_bits;
		mutex_unlock(&dev_priv->fb_tracking.lock);
	}

	intel_frontbuffer_flush(dev, frontbuffer_bits);
}

/**
 * intel_frontbuffer_flip_prepare - prepare asynchronous frontbuffer flip
 * @dev: DRM device
 * @frontbuffer_bits: frontbuffer plane tracking bits
 *
 * This function gets called after scheduling a flip on @obj. The actual
 * frontbuffer flushing will be delayed until completion is signalled with
 * intel_frontbuffer_flip_complete. If an invalidate happens in between this
 * flush will be cancelled.
 *
 * Can be called without any locks held.
 */
void intel_frontbuffer_flip_prepare(struct drm_device *dev,
				    unsigned frontbuffer_bits)
{
	struct drm_i915_private *dev_priv = dev->dev_private;

	mutex_lock(&dev_priv->fb_tracking.lock);
	dev_priv->fb_tracking.flip_bits |= frontbuffer_bits;
	/* Remove stale busy bits due to the old buffer. */
	dev_priv->fb_tracking.busy_bits &= ~frontbuffer_bits;
	mutex_unlock(&dev_priv->fb_tracking.lock);

	intel_psr_single_frame_update(dev);
}

/**
 * intel_frontbuffer_flip_complete - complete asynchronous frontbuffer flip
 * @dev: DRM device
 * @frontbuffer_bits: frontbuffer plane tracking bits
 *
 * This function gets called after the flip has been latched and will complete
 * on the next vblank. It will execute the flush if it hasn't been cancelled yet.
 *
 * Can be called without any locks held.
 */
void intel_frontbuffer_flip_complete(struct drm_device *dev,
				     unsigned frontbuffer_bits)
{
	struct drm_i915_private *dev_priv = dev->dev_private;

	mutex_lock(&dev_priv->fb_tracking.lock);
	/* Mask any cancelled flips. */
	frontbuffer_bits &= dev_priv->fb_tracking.flip_bits;
	dev_priv->fb_tracking.flip_bits &= ~frontbuffer_bits;
	mutex_unlock(&dev_priv->fb_tracking.lock);

	intel_frontbuffer_flush(dev, frontbuffer_bits);
}

/**
 * intel_frontbuffer_flip - synchronous frontbuffer flip
 * @dev: DRM device
 * @frontbuffer_bits: frontbuffer plane tracking bits
 *
 * This function gets called after scheduling a flip on @obj. This is for
 * synchronous plane updates which will happen on the next vblank and which will
 * not get delayed by pending gpu rendering.
 *
 * Can be called without any locks held.
 */

void intel_frontbuffer_flip(struct drm_device *dev,
			    unsigned frontbuffer_bits)
{
	struct drm_i915_private *dev_priv = dev->dev_private;

	mutex_lock(&dev_priv->fb_tracking.lock);
	/* Remove stale busy bits due to the old buffer. */
	dev_priv->fb_tracking.busy_bits &= ~frontbuffer_bits;
	mutex_unlock(&dev_priv->fb_tracking.lock);

	intel_frontbuffer_flush(dev, frontbuffer_bits);
}
Commit	Line	Data
b680c37a DV	1	/*
	2	* Copyright © 2014 Intel Corporation
	3	*
	4	* Permission is hereby granted, free of charge, to any person obtaining a
	5	* copy of this software and associated documentation files (the "Software"),
	6	* to deal in the Software without restriction, including without limitation
	7	* the rights to use, copy, modify, merge, publish, distribute, sublicense,
	8	* and/or sell copies of the Software, and to permit persons to whom the
	9	* Software is furnished to do so, subject to the following conditions:
	10	*
	11	* The above copyright notice and this permission notice (including the next
	12	* paragraph) shall be included in all copies or substantial portions of the
	13	* Software.
	14	*
	15	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	16	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	17	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	18	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	19	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
	20	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
	21	* DEALINGS IN THE SOFTWARE.
	22	*
	23	* Authors:
	24	* Daniel Vetter <daniel.vetter@ffwll.ch>
	25	*/
	26
	27	/**
	28	* DOC: frontbuffer tracking
	29	*
	30	* Many features require us to track changes to the currently active
5c323b2a	31	* frontbuffer, especially rendering targeted at the frontbuffer.
b680c37a DV	32	*
	33	* To be able to do so GEM tracks frontbuffers using a bitmask for all possible
	34	* frontbuffer slots through i915_gem_track_fb(). The function in this file are
	35	* then called when the contents of the frontbuffer are invalidated, when
	36	* frontbuffer rendering has stopped again to flush out all the changes and when
	37	* the frontbuffer is exchanged with a flip. Subsystems interested in
	38	* frontbuffer changes (e.g. PSR, FBC, DRRS) should directly put their callbacks
	39	* into the relevant places and filter for the frontbuffer slots that they are
	40	* interested int.
	41	*
	42	* On a high level there are two types of powersaving features. The first one
	43	* work like a special cache (FBC and PSR) and are interested when they should
	44	* stop caching and when to restart caching. This is done by placing callbacks
	45	* into the invalidate and the flush functions: At invalidate the caching must
	46	* be stopped and at flush time it can be restarted. And maybe they need to know
	47	* when the frontbuffer changes (e.g. when the hw doesn't initiate an invalidate
	48	* and flush on its own) which can be achieved with placing callbacks into the
	49	* flip functions.
	50	*
	51	* The other type of display power saving feature only cares about busyness
	52	* (e.g. DRRS). In that case all three (invalidate, flush and flip) indicate
	53	* busyness. There is no direct way to detect idleness. Instead an idle timer
	54	* work delayed work should be started from the flush and flip functions and
	55	* cancelled as soon as busyness is detected.
	56	*
	57	* Note that there's also an older frontbuffer activity tracking scheme which
5c323b2a	58	* just tracks general activity. This is done by the various mark_busy and
b680c37a DV	59	* mark_idle functions. For display power management features using these
	60	* functions is deprecated and should be avoided.
	61	*/
	62
	63	#include <drm/drmP.h>
	64
	65	#include "intel_drv.h"
	66	#include "i915_drv.h"
	67
	68	static void intel_increase_pllclock(struct drm_device *dev,
	69	enum pipe pipe)
	70	{
	71	struct drm_i915_private *dev_priv = dev->dev_private;
	72	int dpll_reg = DPLL(pipe);
	73	int dpll;
	74
	75	if (!HAS_GMCH_DISPLAY(dev))
	76	return;
	77
	78	if (!dev_priv->lvds_downclock_avail)
	79	return;
	80
	81	dpll = I915_READ(dpll_reg);
	82	if (!HAS_PIPE_CXSR(dev) && (dpll & DISPLAY_RATE_SELECT_FPA1)) {
	83	DRM_DEBUG_DRIVER("upclocking LVDS\n");
	84
	85	assert_panel_unlocked(dev_priv, pipe);
	86
	87	dpll &= ~DISPLAY_RATE_SELECT_FPA1;
	88	I915_WRITE(dpll_reg, dpll);
	89	intel_wait_for_vblank(dev, pipe);
	90
	91	dpll = I915_READ(dpll_reg);
	92	if (dpll & DISPLAY_RATE_SELECT_FPA1)
	93	DRM_DEBUG_DRIVER("failed to upclock LVDS!\n");
	94	}
	95	}
	96
	97	/**
	98	* intel_mark_fb_busy - mark given planes as busy
	99	* @dev: DRM device
	100	* @frontbuffer_bits: bits for the affected planes
b680c37a DV	101	*
	102	* This function gets called every time the screen contents change. It can be
	103	* used to keep e.g. the update rate at the nominal refresh rate with DRRS.
	104	*/
	105	static void intel_mark_fb_busy(struct drm_device *dev,
77a0d1ca	106	unsigned frontbuffer_bits)
b680c37a DV	107	{
	108	struct drm_i915_private *dev_priv = dev->dev_private;
	109	enum pipe pipe;
	110
b680c37a DV	111	for_each_pipe(dev_priv, pipe) {
	112	if (!(frontbuffer_bits & INTEL_FRONTBUFFER_ALL_MASK(pipe)))
	113	continue;
	114
	115	intel_increase_pllclock(dev, pipe);
b680c37a DV	116	}
	117	}
	118
	119	/**
	120	* intel_fb_obj_invalidate - invalidate frontbuffer object
	121	* @obj: GEM object to invalidate
a4001f1b	122	* @origin: which operation caused the invalidation
b680c37a DV	123	*
	124	* This function gets called every time rendering on the given object starts and
	125	* frontbuffer caching (fbc, low refresh rate for DRRS, panel self refresh) must
77a0d1ca	126	* be invalidated. For ORIGIN_CS any subsequent invalidation will be delayed
b680c37a DV	127	* until the rendering completes or a flip on this frontbuffer plane is
	128	* scheduled.
	129	*/
	130	void intel_fb_obj_invalidate(struct drm_i915_gem_object *obj,
a4001f1b	131	enum fb_op_origin origin)
b680c37a DV	132	{
	133	struct drm_device *dev = obj->base.dev;
	134	struct drm_i915_private *dev_priv = dev->dev_private;
	135
	136	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
	137
	138	if (!obj->frontbuffer_bits)
	139	return;
	140
77a0d1ca	141	if (origin == ORIGIN_CS) {
b680c37a DV	142	mutex_lock(&dev_priv->fb_tracking.lock);
	143	dev_priv->fb_tracking.busy_bits
	144	\|= obj->frontbuffer_bits;
	145	dev_priv->fb_tracking.flip_bits
	146	&= ~obj->frontbuffer_bits;
	147	mutex_unlock(&dev_priv->fb_tracking.lock);
	148	}
	149
77a0d1ca	150	intel_mark_fb_busy(dev, obj->frontbuffer_bits);
b680c37a	151
0bc12bcb	152	intel_psr_invalidate(dev, obj->frontbuffer_bits);
a93fad0f	153	intel_edp_drrs_invalidate(dev, obj->frontbuffer_bits);
dbef0f15	154	intel_fbc_invalidate(dev_priv, obj->frontbuffer_bits, origin);
b680c37a DV	155	}
	156
	157	/**
	158	* intel_frontbuffer_flush - flush frontbuffer
	159	* @dev: DRM device
	160	* @frontbuffer_bits: frontbuffer plane tracking bits
	161	*
	162	* This function gets called every time rendering on the given planes has
	163	* completed and frontbuffer caching can be started again. Flushes will get
5c323b2a	164	* delayed if they're blocked by some outstanding asynchronous rendering.
b680c37a DV	165	*
	166	* Can be called without any locks held.
	167	*/
	168	void intel_frontbuffer_flush(struct drm_device *dev,
	169	unsigned frontbuffer_bits)
	170	{
	171	struct drm_i915_private *dev_priv = dev->dev_private;
	172
	173	/* Delay flushing when rings are still busy.*/
	174	mutex_lock(&dev_priv->fb_tracking.lock);
	175	frontbuffer_bits &= ~dev_priv->fb_tracking.busy_bits;
	176	mutex_unlock(&dev_priv->fb_tracking.lock);
	177
77a0d1ca	178	intel_mark_fb_busy(dev, frontbuffer_bits);
b680c37a	179
a93fad0f	180	intel_edp_drrs_flush(dev, frontbuffer_bits);
0bc12bcb	181	intel_psr_flush(dev, frontbuffer_bits);
dbef0f15	182	intel_fbc_flush(dev_priv, frontbuffer_bits);
b680c37a DV	183	}
	184
	185	/**
	186	* intel_fb_obj_flush - flush frontbuffer object
	187	* @obj: GEM object to flush
	188	* @retire: set when retiring asynchronous rendering
	189	*
	190	* This function gets called every time rendering on the given object has
	191	* completed and frontbuffer caching can be started again. If @retire is true
	192	* then any delayed flushes will be unblocked.
	193	*/
	194	void intel_fb_obj_flush(struct drm_i915_gem_object *obj,
	195	bool retire)
	196	{
	197	struct drm_device *dev = obj->base.dev;
	198	struct drm_i915_private *dev_priv = dev->dev_private;
	199	unsigned frontbuffer_bits;
	200
	201	WARN_ON(!mutex_is_locked(&dev->struct_mutex));
	202
	203	if (!obj->frontbuffer_bits)
	204	return;
	205
	206	frontbuffer_bits = obj->frontbuffer_bits;
	207
	208	if (retire) {
	209	mutex_lock(&dev_priv->fb_tracking.lock);
	210	/* Filter out new bits since rendering started. */
	211	frontbuffer_bits &= dev_priv->fb_tracking.busy_bits;
	212
	213	dev_priv->fb_tracking.busy_bits &= ~frontbuffer_bits;
	214	mutex_unlock(&dev_priv->fb_tracking.lock);
	215	}
	216
	217	intel_frontbuffer_flush(dev, frontbuffer_bits);
	218	}
	219
	220	/**
5c323b2a	221	* intel_frontbuffer_flip_prepare - prepare asynchronous frontbuffer flip
b680c37a DV	222	* @dev: DRM device
	223	* @frontbuffer_bits: frontbuffer plane tracking bits
	224	*
	225	* This function gets called after scheduling a flip on @obj. The actual
	226	* frontbuffer flushing will be delayed until completion is signalled with
	227	* intel_frontbuffer_flip_complete. If an invalidate happens in between this
	228	* flush will be cancelled.
	229	*
	230	* Can be called without any locks held.
	231	*/
	232	void intel_frontbuffer_flip_prepare(struct drm_device *dev,
	233	unsigned frontbuffer_bits)
	234	{
	235	struct drm_i915_private *dev_priv = dev->dev_private;
	236
	237	mutex_lock(&dev_priv->fb_tracking.lock);
11c9b6c6 DV	238	dev_priv->fb_tracking.flip_bits \|= frontbuffer_bits;
	239	/* Remove stale busy bits due to the old buffer. */
	240	dev_priv->fb_tracking.busy_bits &= ~frontbuffer_bits;
b680c37a	241	mutex_unlock(&dev_priv->fb_tracking.lock);
c7240c3b RV	242
c7240c3b RV	243	intel_psr_single_frame_update(dev);
b680c37a DV	244	}
	245
	246	/**
5c323b2a	247	* intel_frontbuffer_flip_complete - complete asynchronous frontbuffer flip
b680c37a DV	248	* @dev: DRM device
	249	* @frontbuffer_bits: frontbuffer plane tracking bits
	250	*
	251	* This function gets called after the flip has been latched and will complete
5c323b2a	252	* on the next vblank. It will execute the flush if it hasn't been cancelled yet.
b680c37a DV	253	*
	254	* Can be called without any locks held.
	255	*/
	256	void intel_frontbuffer_flip_complete(struct drm_device *dev,
	257	unsigned frontbuffer_bits)
	258	{
	259	struct drm_i915_private *dev_priv = dev->dev_private;
	260
	261	mutex_lock(&dev_priv->fb_tracking.lock);
	262	/* Mask any cancelled flips. */
	263	frontbuffer_bits &= dev_priv->fb_tracking.flip_bits;
	264	dev_priv->fb_tracking.flip_bits &= ~frontbuffer_bits;
	265	mutex_unlock(&dev_priv->fb_tracking.lock);
	266
	267	intel_frontbuffer_flush(dev, frontbuffer_bits);
	268	}
fdbff928 DV	269
	270	/**
	271	* intel_frontbuffer_flip - synchronous frontbuffer flip
	272	* @dev: DRM device
	273	* @frontbuffer_bits: frontbuffer plane tracking bits
	274	*
	275	* This function gets called after scheduling a flip on @obj. This is for
	276	* synchronous plane updates which will happen on the next vblank and which will
	277	* not get delayed by pending gpu rendering.
	278	*
	279	* Can be called without any locks held.
	280	*/
	281
	282	void intel_frontbuffer_flip(struct drm_device *dev,
	283	unsigned frontbuffer_bits)
	284	{
	285	struct drm_i915_private *dev_priv = dev->dev_private;
	286
	287	mutex_lock(&dev_priv->fb_tracking.lock);
	288	/* Remove stale busy bits due to the old buffer. */
	289	dev_priv->fb_tracking.busy_bits &= ~frontbuffer_bits;
	290	mutex_unlock(&dev_priv->fb_tracking.lock);
	291
	292	intel_frontbuffer_flush(dev, frontbuffer_bits);
	293	}