path: root/drivers/gpu/drm/drm_irq.c

/**
 * \file drm_irq.c
 * IRQ support
 *
 * \author Rickard E. (Rik) Faith <faith@valinux.com>
 * \author Gareth Hughes <gareth@valinux.com>
 */

/*
 * Created: Fri Mar 19 14:30:16 1999 by faith@valinux.com
 *
 * Copyright 1999, 2000 Precision Insight, Inc., Cedar Park, Texas.
 * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
 * All Rights Reserved.
 *
 * 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
 * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS 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.
 */

#include <drm/drmP.h>
#include "drm_trace.h"

#include <linux/interrupt.h>	/* For task queue support */
#include <linux/slab.h>

#include <linux/vgaarb.h>
#include <linux/export.h>

/* Access macro for slots in vblank timestamp ringbuffer. */
#define vblanktimestamp(dev, crtc, count) \
	((dev)->vblank[crtc].time[(count) % DRM_VBLANKTIME_RBSIZE])

/* Retry timestamp calculation up to 3 times to satisfy
 * drm_timestamp_precision before giving up.
 */
#define DRM_TIMESTAMP_MAXRETRIES 3

/* Threshold in nanoseconds for detection of redundant
 * vblank irq in drm_handle_vblank(). 1 msec should be ok.
 */
#define DRM_REDUNDANT_VBLIRQ_THRESH_NS 1000000

/*
 * Clear vblank timestamp buffer for a crtc.
 */
static void clear_vblank_timestamps(struct drm_device *dev, int crtc)
{
	memset(dev->vblank[crtc].time, 0, sizeof(dev->vblank[crtc].time));
}

/*
 * Disable vblank irq's on crtc, make sure that last vblank count
 * of hardware and corresponding consistent software vblank counter
 * are preserved, even if there are any spurious vblank irq's after
 * disable.
 */
static void vblank_disable_and_save(struct drm_device *dev, int crtc)
{
	unsigned long irqflags;
	u32 vblcount;
	s64 diff_ns;
	int vblrc;
	struct timeval tvblank;
	int count = DRM_TIMESTAMP_MAXRETRIES;

	/* Prevent vblank irq processing while disabling vblank irqs,
	 * so no updates of timestamps or count can happen after we've
	 * disabled. Needed to prevent races in case of delayed irq's.
	 */
	spin_lock_irqsave(&dev->vblank_time_lock, irqflags);

	dev->driver->disable_vblank(dev, crtc);
	dev->vblank[crtc].enabled = false;

	/* No further vblank irq's will be processed after
	 * this point. Get current hardware vblank count and
	 * vblank timestamp, repeat until they are consistent.
	 *
	 * FIXME: There is still a race condition here and in
	 * drm_update_vblank_count() which can cause off-by-one
	 * reinitialization of software vblank counter. If gpu
	 * vblank counter doesn't increment exactly at the leading
	 * edge of a vblank interval, then we can lose 1 count if
	 * we happen to execute between start of vblank and the
	 * delayed gpu counter increment.
	 */
	do {
		dev->vblank[crtc].last = dev->driver->get_vblank_counter(dev, crtc);
		vblrc = drm_get_last_vbltimestamp(dev, crtc, &tvblank, 0);
	} while (dev->vblank[crtc].last != dev->driver->get_vblank_counter(dev, crtc) && (--count) && vblr