path: root/drivers/media/video/omap3isp/ispqueue.c

/*
 * ispqueue.c
 *
 * TI OMAP3 ISP - Video buffers queue handling
 *
 * Copyright (C) 2010 Nokia Corporation
 *
 * Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
 *	     Sakari Ailus <sakari.ailus@iki.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#include <asm/cacheflush.h>
#include <linux/dma-mapping.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/poll.h>
#include <linux/scatterlist.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>

#include "ispqueue.h"

/* -----------------------------------------------------------------------------
 * Video buffers management
 */

/*
 * isp_video_buffer_cache_sync - Keep the buffers coherent between CPU and ISP
 *
 * The typical operation required here is Cache Invalidation across
 * the (user space) buffer address range. And this _must_ be done
 * at QBUF stage (and *only* at QBUF).
 *
 * We try to use optimal cache invalidation function:
 * - dmac_map_area:
 *    - used when the number of pages are _low_.
 *    - it becomes quite slow as the number of pages increase.
 *       - for 648x492 viewfinder (150 pages) it takes 1.3 ms.
 *       - for 5 Mpix buffer (2491 pages) it takes between 25-50 ms.
 *
 * - flush_cache_all:
 *    - used when the number of pages are _high_.
 *    - time taken in the range of 500-900 us.
 *    - has a higher penalty but, as whole dcache + icache is invalidated
 */
/*
 * FIXME: dmac_inv_range crashes randomly on the user space buffer
 *        address. Fall back to flush_cache_all for now.
 */
#define ISP_CACHE_FLUSH_PAGES_MAX       0

static void isp_video_buffer_cache_sync(struct isp_video_buffer *buf)
{
	if (buf->skip_cache)
		return;

	if (buf->vbuf.m.userptr == 0 || buf->npages == 0 ||
	    buf->npages > ISP_CACHE_FLUSH_PAGES_MAX)
		flush_cache_all();
	else {
		dmac_map_area((void *)buf->vbuf.m.userptr, buf->vbuf.length,
			      DMA_FROM_DEVICE);
		outer_inv_range(buf->vbuf.m.userptr,
				buf->vbuf.m.userptr + buf->vbuf.length);
	}
}

/*
 * isp_video_buffer_lock_vma - Prevent VMAs from being unmapped
 *
 * Lock the VMAs underlying the given buffer into memory. This avoids the
 * userspace buffer mapping from being swapped out, making VIPT cache handling
 * easier.
 *
 * Note that the pages will not be freed as the buffers have been locked to
 * memory using by a call to get_user_pages(), but the userspace mapping could
 * still disappear if the VMAs are not locked. This is caused by the memory
 * management code trying to be as lock-less as possible, which results in the
 * userspace mapping manager not finding out that the pages are locked under
 * some conditions.
 */
static int isp_video_buffer_lock_vma(struct isp_video_buffer *buf, int lock)
{
	struct vm_area_struct *vma;
	unsigned long start;
	unsigned long end;
	int ret = 0;

	if (buf->vbuf.memory == V4L2_MEMORY_MMAP)
		return 0;

	/* We can be called from workqueue context if the current task dies to
	 * unlock the VMAs. In that case there's no current memory management
	 * context so unlocking can't be performed, but the VMAs have been or
	 * are getting destroyed anyway so it doesn't really matter.
	 */
	if (!current || !current->mm)
		return lock ? -EINVAL : 0;

	start = buf->vbuf.m.userptr;
	end = buf->vbuf.m.userptr + buf->vbuf.length - 1;

	down_write(&current->mm->mmap_sem);
	spin_lock(&current->mm->page_table_lock);

	do {
		vma = find_vma(current->mm, start);
		if (vma == NULL) {
			ret = -EFAULT;
			goto out;
		}

		if (lock)
			vma->vm_flags |= VM_LOCKED;
		else
			vma->vm_flags &= ~VM_LOCKED;

		start = vma->vm_end + 1;
	} while (vma->vm_end < end);

	if (lock)
		buf->vm_flags |= VM_LOCKED;
	else
		buf->vm_flags &= ~VM_LOCKED;

out:
	spin_unlock(&current->mm->page_table_lock);
	up_write(&current->mm->mmap_sem);
	return ret;
}

/*
 * isp_video_buffer_sglist_kernel - Build a scatter list for a vmalloc'ed buffer
 *
 * Iterate over the vmalloc'ed area and create a scatter list entry for every
 * page.
 */
static int isp_video_buffer_sglist_kernel(struct isp_video_buffer *buf)
{