linux/drivers/gpu/drm/omapdrm/omap_gem.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2011 Texas Instruments Incorporated - https://www.ti.com/
 * Author: Rob Clark <rob.clark@linaro.org>
 */

#include <linux/dma-mapping.h>
#include <linux/seq_file.h>
#include <linux/shmem_fs.h>
#include <linux/spinlock.h>
#include <linux/vmalloc.h>

#include <drm/drm_prime.h>
#include <drm/drm_vma_manager.h>

#include "omap_drv.h"
#include "omap_dmm_tiler.h"

/*
 * GEM buffer object implementation.
 */

/* note: we use upper 8 bits of flags for driver-internal flags: */
#define OMAP_BO_MEM_DMA_API	0x01000000	/* memory allocated with the dma_alloc_* API */
#define OMAP_BO_MEM_SHMEM	0x02000000	/* memory allocated through shmem backing */
#define OMAP_BO_MEM_DMABUF	0x08000000	/* memory imported from a dmabuf */

struct omap_gem_object {
	struct drm_gem_object base;

	struct list_head mm_list;

	u32 flags;

	/** width/height for tiled formats (rounded up to slot boundaries) */
	u16 width, height;

	/** roll applied when mapping to DMM */
	u32 roll;

	/** protects pin_cnt, block, pages, dma_addrs and vaddr */
	struct mutex lock;

	/**
	 * dma_addr contains the buffer DMA address. It is valid for
	 *
	 * - buffers allocated through the DMA mapping API (with the
	 *   OMAP_BO_MEM_DMA_API flag set)
	 *
	 * - buffers imported from dmabuf (with the OMAP_BO_MEM_DMABUF flag set)
	 *   if they are physically contiguous
	 *
	 * - buffers mapped through the TILER when pin_cnt is not zero, in which
	 *   case the DMA address points to the TILER aperture
	 *
	 * Physically contiguous buffers have their DMA address equal to the
	 * physical address as we don't remap those buffers through the TILER.
	 *
	 * Buffers mapped to the TILER have their DMA address pointing to the
	 * TILER aperture. As TILER mappings are refcounted (through pin_cnt)
	 * the DMA address must be accessed through omap_gem_pin() to ensure
	 * that the mapping won't disappear unexpectedly. References must be
	 * released with omap_gem_unpin().
	 */
	dma_addr_t dma_addr;

	/**
	 * # of users
	 */
	refcount_t pin_cnt;

	/**
	 * If the buffer has been imported from a dmabuf the OMAP_DB_DMABUF flag
	 * is set and the sgt field is valid.
	 */
	struct sg_table *sgt;

	/**
	 * tiler block used when buffer is remapped in DMM/TILER.
	 */
	struct tiler_block *block;

	/**
	 * Array of backing pages, if allocated.  Note that pages are never
	 * allocated for buffers originally allocated from contiguous memory
	 */
	struct page **pages;

	/** addresses corresponding to pages in above array */
	dma_addr_t *dma_addrs;

	/**
	 * Virtual address, if mapped.
	 */
	void *vaddr;
};

#define to_omap_bo(x) container_of(x, struct omap_gem_object, base)

/* To deal with userspace mmap'ings of 2d tiled buffers, which (a) are
 * not necessarily pinned in TILER all the time, and (b) when they are
 * they are not necessarily page aligned, we reserve one or more small
 * regions in each of the 2d containers to use as a user-GART where we
 * can create a second page-aligned mapping of parts of the buffer
 * being accessed from userspace.
 *
 * Note that we could optimize slightly when we know that multiple
 * tiler containers are backed by the same PAT.. but I'll leave that
 * for later..
 */
#define NUM_USERGART_ENTRIES 2
struct omap_drm_usergart_entry {
	struct tiler_block *block;	/* the reserved tiler block */
	dma_addr_t dma_addr;
	struct drm_gem_object *obj;	/* the current pinned obj */
	pgoff_t obj_pgoff;		/* page offset of obj currently
					   mapped in */
};

struct omap_drm_usergart {
	struct omap_drm_usergart_entry entry[NUM_USERGART_ENTRIES];
	int height;				/* height in rows */
	int height_shift;		/* ilog2(height in rows) */
	int slot_shift;			/* ilog2(width per slot) */
	int stride_pfn;			/* stride in pages */
	int last;				/* index of last used entry */
};

/* -----------------------------------------------------------------------------
 * Helpers
 */

/** get mmap offset */
u64 omap_gem_mmap_offset(struct drm_gem_object *obj)
{
	struct drm_device *dev = obj->dev;
	int ret;
	size_t size;

	/* Make it mmapable */
	size = omap_gem_mmap_size(obj);
	ret = drm_gem_create_mmap_offset_size(obj, size);
	if (ret) {
		dev_err(dev->dev, "could not allocate mmap offset\n");
		return 0;
	}

	return drm_vma_node_offset_addr(&obj->vma_node);
}

static bool omap_gem_sgt_is_contiguous(struct sg_table *sgt, size_t size)
{
	return !(drm_prime_get_contiguous_size(sgt) < size);
}

static bool omap_gem_is_contiguous(struct omap_gem_object *omap_obj)
{
	if (omap_obj->flags & OMAP_BO_MEM_DMA_API)
		return true;

	if ((omap_obj->flags & OMAP_BO_MEM_DMABUF) &&
	    omap_gem_sgt_is_contiguous(omap_obj->sgt, omap_obj->base.size))
		return true;

	return false;
}

/* -----------------------------------------------------------------------------
 * Eviction
 */

static void omap_gem_evict_entry(struct drm_gem_object *obj,
		enum tiler_fmt fmt, struct omap_drm_usergart_entry *entry)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	struct omap_drm_private *priv = obj->dev->dev_private;
	int n = priv->usergart[fmt].height;
	size_t size = PAGE_SIZE * n;
	loff_t off = omap_gem_mmap_offset(obj) +
			(entry->obj_pgoff << PAGE_SHIFT);
	const int m = DIV_ROUND_UP(omap_obj->width << fmt, PAGE_SIZE);

	if (m > 1) {
		int i;
		/* if stride > than PAGE_SIZE then sparse mapping: */
		for (i = n; i > 0; i--) {
			unmap_mapping_range(obj->dev->anon_inode->i_mapping,
					    off, PAGE_SIZE, 1);
			off += PAGE_SIZE * m;
		}
	} else {
		unmap_mapping_range(obj->dev->anon_inode->i_mapping,
				    off, size, 1);
	}

	entry->obj = NULL;
}

/* Evict a buffer from usergart, if it is mapped there */
static void omap_gem_evict(struct drm_gem_object *obj)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	struct omap_drm_private *priv = obj->dev->dev_private;

	if (omap_obj->flags & OMAP_BO_TILED_MASK) {
		enum tiler_fmt fmt = gem2fmt(omap_obj->flags);
		int i;

		for (i = 0; i < NUM_USERGART_ENTRIES; i++) {
			struct omap_drm_usergart_entry *entry =
				&priv->usergart[fmt].entry[i];

			if (entry->obj == obj)
				omap_gem_evict_entry(obj, fmt, entry);
		}
	}
}

/* -----------------------------------------------------------------------------
 * Page Management
 */

/*
 * Ensure backing pages are allocated. Must be called with the omap_obj.lock
 * held.
 */
static int omap_gem_attach_pages(struct drm_gem_object *obj)
{
	struct drm_device *dev = obj->dev;
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	struct page **pages;
	int npages = obj->size >> PAGE_SHIFT;
	int i, ret;
	dma_addr_t *addrs;

	lockdep_assert_held(&omap_obj->lock);

	/*
	 * If not using shmem (in which case backing pages don't need to be
	 * allocated) or if pages are already allocated we're done.
	 */
	if (!(omap_obj->flags & OMAP_BO_MEM_SHMEM) || omap_obj->pages)
		return 0;

	pages = drm_gem_get_pages(obj);
	if (IS_ERR(pages)) {
		dev_err(obj->dev->dev, "could not get pages: %ld\n", PTR_ERR(pages));
		return PTR_ERR(pages);
	}

	/* for non-cached buffers, ensure the new pages are clean because
	 * DSS, GPU, etc. are not cache coherent:
	 */
	if (omap_obj->flags & (OMAP_BO_WC|OMAP_BO_UNCACHED)) {
		addrs = kmalloc_array(npages, sizeof(*addrs), GFP_KERNEL);
		if (!addrs) {
			ret = -ENOMEM;
			goto free_pages;
		}

		for (i = 0; i < npages; i++) {
			addrs[i] = dma_map_page(dev->dev, pages[i],
					0, PAGE_SIZE, DMA_TO_DEVICE);

			if (dma_mapping_error(dev->dev, addrs[i])) {
				dev_warn(dev->dev,
					"%s: failed to map page\n", __func__);

				for (i = i - 1; i >= 0; --i) {
					dma_unmap_page(dev->dev, addrs[i],
						PAGE_SIZE, DMA_TO_DEVICE);
				}

				ret = -ENOMEM;
				goto free_addrs;
			}
		}
	} else {
		addrs = kcalloc(npages, sizeof(*addrs), GFP_KERNEL);
		if (!addrs) {
			ret = -ENOMEM;
			goto free_pages;
		}
	}

	omap_obj->dma_addrs = addrs;
	omap_obj->pages = pages;

	return 0;

free_addrs:
	kfree(addrs);
free_pages:
	drm_gem_put_pages(obj, pages, true, false);

	return ret;
}

/* Release backing pages. Must be called with the omap_obj.lock held. */
static void omap_gem_detach_pages(struct drm_gem_object *obj)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	unsigned int npages = obj->size >> PAGE_SHIFT;
	unsigned int i;

	lockdep_assert_held(&omap_obj->lock);

	for (i = 0; i < npages; i++) {
		if (omap_obj->dma_addrs[i])
			dma_unmap_page(obj->dev->dev, omap_obj->dma_addrs[i],
				       PAGE_SIZE, DMA_TO_DEVICE);
	}

	kfree(omap_obj->dma_addrs);
	omap_obj->dma_addrs = NULL;

	drm_gem_put_pages(obj, omap_obj->pages, true, false);
	omap_obj->pages = NULL;
}

/* get buffer flags */
u32 omap_gem_flags(struct drm_gem_object *obj)
{
	return to_omap_bo(obj)->flags;
}

/** get mmap size */
size_t omap_gem_mmap_size(struct drm_gem_object *obj)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	size_t size = obj->size;

	if (omap_obj->flags & OMAP_BO_TILED_MASK) {
		/* for tiled buffers, the virtual size has stride rounded up
		 * to 4kb.. (to hide the fact that row n+1 might start 16kb or
		 * 32kb later!).  But we don't back the entire buffer with
		 * pages, only the valid picture part.. so need to adjust for
		 * this in the size used to mmap and generate mmap offset
		 */
		size = tiler_vsize(gem2fmt(omap_obj->flags),
				omap_obj->width, omap_obj->height);
	}

	return size;
}

/* -----------------------------------------------------------------------------
 * Fault Handling
 */

/* Normal handling for the case of faulting in non-tiled buffers */
static vm_fault_t omap_gem_fault_1d(struct drm_gem_object *obj,
		struct vm_area_struct *vma, struct vm_fault *vmf)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	unsigned long pfn;
	pgoff_t pgoff;

	/* We don't use vmf->pgoff since that has the fake offset: */
	pgoff = (vmf->address - vma->vm_start) >> PAGE_SHIFT;

	if (omap_obj->pages) {
		omap_gem_cpu_sync_page(obj, pgoff);
		pfn = page_to_pfn(omap_obj->pages[pgoff]);
	} else {
		BUG_ON(!omap_gem_is_contiguous(omap_obj));
		pfn = (omap_obj->dma_addr >> PAGE_SHIFT) + pgoff;
	}

	VERB("Inserting %p pfn %lx, pa %lx", (void *)vmf->address,
			pfn, pfn << PAGE_SHIFT);

	return vmf_insert_mixed(vma, vmf->address, pfn);
}

/* Special handling for the case of faulting in 2d tiled buffers */
static vm_fault_t omap_gem_fault_2d(struct drm_gem_object *obj,
		struct vm_area_struct *vma, struct vm_fault *vmf)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	struct omap_drm_private *priv = obj->dev->dev_private;
	struct omap_drm_usergart_entry *entry;
	enum tiler_fmt fmt = gem2fmt(omap_obj->flags);
	struct page *pages[64];  /* XXX is this too much to have on stack? */
	unsigned long pfn;
	pgoff_t pgoff, base_pgoff;
	unsigned long vaddr;
	int i, err, slots;
	vm_fault_t ret = VM_FAULT_NOPAGE;

	/*
	 * Note the height of the slot is also equal to the number of pages
	 * that need to be mapped in to fill 4kb wide CPU page.  If the slot
	 * height is 64, then 64 pages fill a 4kb wide by 64 row region.
	 */
	const int n = priv->usergart[fmt].height;
	const int n_shift = priv->usergart[fmt].height_shift;

	/*
	 * If buffer width in bytes > PAGE_SIZE then the virtual stride is
	 * rounded up to next multiple of PAGE_SIZE.. this need to be taken
	 * into account in some of the math, so figure out virtual stride
	 * in pages
	 */
	const int m = DIV_ROUND_UP(omap_obj->width << fmt, PAGE_SIZE);

	/* We don't use vmf->pgoff since that has the fake offset: */
	pgoff = (vmf->address - vma->vm_start) >> PAGE_SHIFT;

	/*
	 * Actual address we start mapping at is rounded down to previous slot
	 * boundary in the y direction:
	 */
	base_pgoff = round_down(pgoff, m << n_shift);

	/* figure out buffer width in slots */
	slots = omap_obj->width >> priv->usergart[fmt].slot_shift;

	vaddr = vmf->address - ((pgoff - base_pgoff) << PAGE_SHIFT);

	entry = &priv->usergart[fmt].entry[priv->usergart[fmt].last];

	/* evict previous buffer using this usergart entry, if any: */
	if (entry->obj)
		omap_gem_evict_entry(entry->obj, fmt, entry);

	entry->obj = obj;
	entry->obj_pgoff = base_pgoff;

	/* now convert base_pgoff to phys offset from virt offset: */
	base_pgoff = (base_pgoff >> n_shift) * slots;

	/* for wider-than 4k.. figure out which part of the slot-row we want: */
	if (m > 1) {
		int off = pgoff % m;
		entry->obj_pgoff += off;
		base_pgoff /= m;
		slots = min(slots - (off << n_shift), n);
		base_pgoff += off << n_shift;
		vaddr += off << PAGE_SHIFT;
	}

	/*
	 * Map in pages. Beyond the valid pixel part of the buffer, we set
	 * pages[i] to NULL to get a dummy page mapped in.. if someone
	 * reads/writes it they will get random/undefined content, but at
	 * least it won't be corrupting whatever other random page used to
	 * be mapped in, or other undefined behavior.
	 */
	memcpy(pages, &omap_obj->pages[base_pgoff],
			sizeof(struct page *) * slots);
	memset(pages + slots, 0,
			sizeof(struct page *) * (n - slots));

	err = tiler_pin(entry->block, pages, ARRAY_SIZE(pages), 0, true);
	if (err) {
		ret = vmf_error(err);
		dev_err(obj->dev->dev, "failed to pin: %d\n", err);
		return ret;
	}

	pfn = entry->dma_addr >> PAGE_SHIFT;

	VERB("Inserting %p pfn %lx, pa %lx", (void *)vmf->address,
			pfn, pfn << PAGE_SHIFT);

	for (i = n; i > 0; i--) {
		ret = vmf_insert_mixed(vma, vaddr, pfn);
		if (ret & VM_FAULT_ERROR)
			break;
		pfn += priv->usergart[fmt].stride_pfn;
		vaddr += PAGE_SIZE * m;
	}

	/* simple round-robin: */
	priv->usergart[fmt].last = (priv->usergart[fmt].last + 1)
				 % NUM_USERGART_ENTRIES;

	return ret;
}

/**
 * omap_gem_fault		-	pagefault handler for GEM objects
 * @vmf: fault detail
 *
 * Invoked when a fault occurs on an mmap of a GEM managed area. GEM
 * does most of the work for us including the actual map/unmap calls
 * but we need to do the actual page work.
 *
 * The VMA was set up by GEM. In doing so it also ensured that the
 * vma->vm_private_data points to the GEM object that is backing this
 * mapping.
 */
static vm_fault_t omap_gem_fault(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	struct drm_gem_object *obj = vma->vm_private_data;
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	int err;
	vm_fault_t ret;

	/* Make sure we don't parallel update on a fault, nor move or remove
	 * something from beneath our feet
	 */
	mutex_lock(&omap_obj->lock);

	/* if a shmem backed object, make sure we have pages attached now */
	err = omap_gem_attach_pages(obj);
	if (err) {
		ret = vmf_error(err);
		goto fail;
	}

	/* where should we do corresponding put_pages().. we are mapping
	 * the original page, rather than thru a GART, so we can't rely
	 * on eviction to trigger this.  But munmap() or all mappings should
	 * probably trigger put_pages()?
	 */

	if (omap_obj->flags & OMAP_BO_TILED_MASK)
		ret = omap_gem_fault_2d(obj, vma, vmf);
	else
		ret = omap_gem_fault_1d(obj, vma, vmf);


fail:
	mutex_unlock(&omap_obj->lock);
	return ret;
}

static int omap_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);

	vm_flags_set(vma, VM_DONTEXPAND | VM_DONTDUMP | VM_IO | VM_MIXEDMAP);

	if (omap_obj->flags & OMAP_BO_WC) {
		vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
	} else if (omap_obj->flags & OMAP_BO_UNCACHED) {
		vma->vm_page_prot = pgprot_noncached(vm_get_page_prot(vma->vm_flags));
	} else {
		/*
		 * We do have some private objects, at least for scanout buffers
		 * on hardware without DMM/TILER.  But these are allocated write-
		 * combine
		 */
		if (WARN_ON(!obj->filp))
			return -EINVAL;

		/*
		 * Shunt off cached objs to shmem file so they have their own
		 * address_space (so unmap_mapping_range does what we want,
		 * in particular in the case of mmap'd dmabufs)
		 */
		vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node);
		vma_set_file(vma, obj->filp);

		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
	}

	vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);

	return 0;
}

/* -----------------------------------------------------------------------------
 * Dumb Buffers
 */

/**
 * omap_gem_dumb_create	-	create a dumb buffer
 * @file: our client file
 * @dev: our device
 * @args: the requested arguments copied from userspace
 *
 * Allocate a buffer suitable for use for a frame buffer of the
 * form described by user space. Give userspace a handle by which
 * to reference it.
 */
int omap_gem_dumb_create(struct drm_file *file, struct drm_device *dev,
		struct drm_mode_create_dumb *args)
{
	union omap_gem_size gsize;

	args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);

	args->size = PAGE_ALIGN(args->pitch * args->height);

	gsize = (union omap_gem_size){
		.bytes = args->size,
	};

	return omap_gem_new_handle(dev, file, gsize,
			OMAP_BO_SCANOUT | OMAP_BO_WC, &args->handle);
}

/**
 * omap_gem_dumb_map_offset - create an offset for a dumb buffer
 * @file: our drm client file
 * @dev: drm device
 * @handle: GEM handle to the object (from dumb_create)
 * @offset: memory map offset placeholder
 *
 * Do the necessary setup to allow the mapping of the frame buffer
 * into user memory. We don't have to do much here at the moment.
 */
int omap_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev,
		u32 handle, u64 *offset)
{
	struct drm_gem_object *obj;
	int ret = 0;

	/* GEM does all our handle to object mapping */
	obj = drm_gem_object_lookup(file, handle);
	if (obj == NULL) {
		ret = -ENOENT;
		goto fail;
	}

	*offset = omap_gem_mmap_offset(obj);

	drm_gem_object_put(obj);

fail:
	return ret;
}

#ifdef CONFIG_DRM_FBDEV_EMULATION
/* Set scrolling position.  This allows us to implement fast scrolling
 * for console.
 *
 * Call only from non-atomic contexts.
 */
int omap_gem_roll(struct drm_gem_object *obj, u32 roll)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	u32 npages = obj->size >> PAGE_SHIFT;
	int ret = 0;

	if (roll > npages) {
		dev_err(obj->dev->dev, "invalid roll: %d\n", roll);
		return -EINVAL;
	}

	omap_obj->roll = roll;

	mutex_lock(&omap_obj->lock);

	/* if we aren't mapped yet, we don't need to do anything */
	if (omap_obj->block) {
		ret = omap_gem_attach_pages(obj);
		if (ret)
			goto fail;

		ret = tiler_pin(omap_obj->block, omap_obj->pages, npages,
				roll, true);
		if (ret)
			dev_err(obj->dev->dev, "could not repin: %d\n", ret);
	}

fail:
	mutex_unlock(&omap_obj->lock);

	return ret;
}
#endif

/* -----------------------------------------------------------------------------
 * Memory Management & DMA Sync
 */

/*
 * shmem buffers that are mapped cached are not coherent.
 *
 * We keep track of dirty pages using page faulting to perform cache management.
 * When a page is mapped to the CPU in read/write mode the device can't access
 * it and omap_obj->dma_addrs[i] is NULL. When a page is mapped to the device
 * the omap_obj->dma_addrs[i] is set to the DMA address, and the page is
 * unmapped from the CPU.
 */
static inline bool omap_gem_is_cached_coherent(struct drm_gem_object *obj)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);

	return !((omap_obj->flags & OMAP_BO_MEM_SHMEM) &&
		((omap_obj->flags & OMAP_BO_CACHE_MASK) == OMAP_BO_CACHED));
}

/* Sync the buffer for CPU access.. note pages should already be
 * attached, ie. omap_gem_get_pages()
 */
void omap_gem_cpu_sync_page(struct drm_gem_object *obj, int pgoff)
{
	struct drm_device *dev = obj->dev;
	struct omap_gem_object *omap_obj = to_omap_bo(obj);

	if (omap_gem_is_cached_coherent(obj))
		return;

	if (omap_obj->dma_addrs[pgoff]) {
		dma_unmap_page(dev->dev, omap_obj->dma_addrs[pgoff],
				PAGE_SIZE, DMA_TO_DEVICE);
		omap_obj->dma_addrs[pgoff] = 0;
	}
}

/* sync the buffer for DMA access */
void omap_gem_dma_sync_buffer(struct drm_gem_object *obj,
		enum dma_data_direction dir)
{
	struct drm_device *dev = obj->dev;
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	int i, npages = obj->size >> PAGE_SHIFT;
	struct page **pages = omap_obj->pages;
	bool dirty = false;

	if (omap_gem_is_cached_coherent(obj))
		return;

	for (i = 0; i < npages; i++) {
		if (!omap_obj->dma_addrs[i]) {
			dma_addr_t addr;

			addr = dma_map_page(dev->dev, pages[i], 0,
					    PAGE_SIZE, dir);
			if (dma_mapping_error(dev->dev, addr)) {
				dev_warn(dev->dev, "%s: failed to map page\n",
					__func__);
				break;
			}

			dirty = true;
			omap_obj->dma_addrs[i] = addr;
		}
	}

	if (dirty) {
		unmap_mapping_range(obj->filp->f_mapping, 0,
				    omap_gem_mmap_size(obj), 1);
	}
}

static int omap_gem_pin_tiler(struct drm_gem_object *obj)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	u32 npages = obj->size >> PAGE_SHIFT;
	enum tiler_fmt fmt = gem2fmt(omap_obj->flags);
	struct tiler_block *block;
	int ret;

	BUG_ON(omap_obj->block);

	if (omap_obj->flags & OMAP_BO_TILED_MASK) {
		block = tiler_reserve_2d(fmt, omap_obj->width, omap_obj->height,
					 PAGE_SIZE);
	} else {
		block = tiler_reserve_1d(obj->size);
	}

	if (IS_ERR(block)) {
		ret = PTR_ERR(block);
		dev_err(obj->dev->dev, "could not remap: %d (%d)\n", ret, fmt);
		goto fail;
	}

	/* TODO: enable async refill.. */
	ret = tiler_pin(block, omap_obj->pages, npages, omap_obj->roll, true);
	if (ret) {
		tiler_release(block);
		dev_err(obj->dev->dev, "could not pin: %d\n", ret);
		goto fail;
	}

	omap_obj->dma_addr = tiler_ssptr(block);
	omap_obj->block = block;

	DBG("got dma address: %pad", &omap_obj->dma_addr);

fail:
	return ret;
}

/**
 * omap_gem_pin() - Pin a GEM object in memory
 * @obj: the GEM object
 * @dma_addr: the DMA address
 *
 * Pin the given GEM object in memory and fill the dma_addr pointer with the
 * object's DMA address. If the buffer is not physically contiguous it will be
 * remapped through the TILER to provide a contiguous view.
 *
 * Pins are reference-counted, calling this function multiple times is allowed
 * as long the corresponding omap_gem_unpin() calls are balanced.
 *
 * Return 0 on success or a negative error code otherwise.
 */
int omap_gem_pin(struct drm_gem_object *obj, dma_addr_t *dma_addr)
{
	struct omap_drm_private *priv = obj->dev->dev_private;
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	int ret = 0;

	mutex_lock(&omap_obj->lock);

	if (!omap_gem_is_contiguous(omap_obj)) {
		if (refcount_read(&omap_obj->pin_cnt) == 0) {

			refcount_set(&omap_obj->pin_cnt, 1);

			ret = omap_gem_attach_pages(obj);
			if (ret)
				goto fail;

			if (omap_obj->flags & OMAP_BO_SCANOUT) {
				if (priv->has_dmm) {
					ret = omap_gem_pin_tiler(obj);
					if (ret)
						goto fail;
				}
			}
		} else {
			refcount_inc(&omap_obj->pin_cnt);
		}
	}

	if (dma_addr)
		*dma_addr = omap_obj->dma_addr;

fail:
	mutex_unlock(&omap_obj->lock);

	return ret;
}

/**
 * omap_gem_unpin_locked() - Unpin a GEM object from memory
 * @obj: the GEM object
 *
 * omap_gem_unpin() without locking.
 */
static void omap_gem_unpin_locked(struct drm_gem_object *obj)
{
	struct omap_drm_private *priv = obj->dev->dev_private;
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	int ret;

	if (omap_gem_is_contiguous(omap_obj))
		return;

	if (refcount_dec_and_test(&omap_obj->pin_cnt)) {
		if (omap_obj->sgt) {
			sg_free_table(omap_obj->sgt);
			kfree(omap_obj->sgt);
			omap_obj->sgt = NULL;
		}
		if (!(omap_obj->flags & OMAP_BO_SCANOUT))
			return;
		if (priv->has_dmm) {
			ret = tiler_unpin(omap_obj->block);
			if (ret) {
				dev_err(obj->dev->dev,
					"could not unpin pages: %d\n", ret);
			}
			ret = tiler_release(omap_obj->block);
			if (ret) {
				dev_err(obj->dev->dev,
					"could not release unmap: %d\n", ret);
			}
			omap_obj->dma_addr = 0;
			omap_obj->block = NULL;
		}
	}
}

/**
 * omap_gem_unpin() - Unpin a GEM object from memory
 * @obj: the GEM object
 *
 * Unpin the given GEM object previously pinned with omap_gem_pin(). Pins are
 * reference-counted, the actual unpin will only be performed when the number
 * of calls to this function matches the number of calls to omap_gem_pin().
 */
void omap_gem_unpin(struct drm_gem_object *obj)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);

	mutex_lock(&omap_obj->lock);
	omap_gem_unpin_locked(obj);
	mutex_unlock(&omap_obj->lock);
}

/* Get rotated scanout address (only valid if already pinned), at the
 * specified orientation and x,y offset from top-left corner of buffer
 * (only valid for tiled 2d buffers)
 */
int omap_gem_rotated_dma_addr(struct drm_gem_object *obj, u32 orient,
		int x, int y, dma_addr_t *dma_addr)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	int ret = -EINVAL;

	mutex_lock(&omap_obj->lock);

	if ((refcount_read(&omap_obj->pin_cnt) > 0) && omap_obj->block &&
			(omap_obj->flags & OMAP_BO_TILED_MASK)) {
		*dma_addr = tiler_tsptr(omap_obj->block, orient, x, y);
		ret = 0;
	}

	mutex_unlock(&omap_obj->lock);

	return ret;
}

/* Get tiler stride for the buffer (only valid for 2d tiled buffers) */
int omap_gem_tiled_stride(struct drm_gem_object *obj, u32 orient)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	int ret = -EINVAL;
	if (omap_obj->flags & OMAP_BO_TILED_MASK)
		ret = tiler_stride(gem2fmt(omap_obj->flags), orient);
	return ret;
}

/* if !remap, and we don't have pages backing, then fail, rather than
 * increasing the pin count (which we don't really do yet anyways,
 * because we don't support swapping pages back out).  And 'remap'
 * might not be quite the right name, but I wanted to keep it working
 * similarly to omap_gem_pin().  Note though that mutex is not
 * aquired if !remap (because this can be called in atomic ctxt),
 * but probably omap_gem_unpin() should be changed to work in the
 * same way.  If !remap, a matching omap_gem_put_pages() call is not
 * required (and should not be made).
 */
int omap_gem_get_pages(struct drm_gem_object *obj, struct page ***pages,
		bool remap)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	int ret = 0;

	mutex_lock(&omap_obj->lock);

	if (remap) {
		ret = omap_gem_attach_pages(obj);
		if (ret)
			goto unlock;
	}

	if (!omap_obj->pages) {
		ret = -ENOMEM;
		goto unlock;
	}

	*pages = omap_obj->pages;

unlock:
	mutex_unlock(&omap_obj->lock);

	return ret;
}

/* release pages when DMA no longer being performed */
int omap_gem_put_pages(struct drm_gem_object *obj)
{
	/* do something here if we dynamically attach/detach pages.. at
	 * least they would no longer need to be pinned if everyone has
	 * released the pages..
	 */
	return 0;
}

struct sg_table *omap_gem_get_sg(struct drm_gem_object *obj,
		enum dma_data_direction dir)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	dma_addr_t addr;
	struct sg_table *sgt;
	struct scatterlist *sg;
	unsigned int count, len, stride, i;
	int ret;

	ret = omap_gem_pin(obj, &addr);
	if (ret)
		return ERR_PTR(ret);

	mutex_lock(&omap_obj->lock);

	sgt = omap_obj->sgt;
	if (sgt)
		goto out;

	sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
	if (!sgt) {
		ret = -ENOMEM;
		goto err_unpin;
	}

	if (addr) {
		if (omap_obj->flags & OMAP_BO_TILED_MASK) {
			enum tiler_fmt fmt = gem2fmt(omap_obj->flags);

			len = omap_obj->width << (int)fmt;
			count = omap_obj->height;
			stride = tiler_stride(fmt, 0);
		} else {
			len = obj->size;
			count = 1;
			stride = 0;
		}
	} else {
		count = obj->size >> PAGE_SHIFT;
	}

	ret = sg_alloc_table(sgt, count, GFP_KERNEL);
	if (ret)
		goto err_free;

	/* this must be after omap_gem_pin() to ensure we have pages attached */
	omap_gem_dma_sync_buffer(obj, dir);

	if (addr) {
		for_each_sg(sgt->sgl, sg, count, i) {
			sg_set_page(sg, pfn_to_page(__phys_to_pfn(addr)),
				    len, offset_in_page(addr));
			sg_dma_address(sg) = addr;
			sg_dma_len(sg) = len;

			addr += stride;
		}
	} else {
		for_each_sg(sgt->sgl, sg, count, i) {
			sg_set_page(sg, omap_obj->pages[i], PAGE_SIZE, 0);
			sg_dma_address(sg) = omap_obj->dma_addrs[i];
			sg_dma_len(sg) =  PAGE_SIZE;
		}
	}

	omap_obj->sgt = sgt;
out:
	mutex_unlock(&omap_obj->lock);
	return sgt;

err_free:
	kfree(sgt);
err_unpin:
	mutex_unlock(&omap_obj->lock);
	omap_gem_unpin(obj);
	return ERR_PTR(ret);
}

void omap_gem_put_sg(struct drm_gem_object *obj, struct sg_table *sgt)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);

	if (WARN_ON(omap_obj->sgt != sgt))
		return;

	omap_gem_unpin(obj);
}

#ifdef CONFIG_DRM_FBDEV_EMULATION
/*
 * Get kernel virtual address for CPU access.. this more or less only
 * exists for omap_fbdev.
 */
void *omap_gem_vaddr(struct drm_gem_object *obj)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	void *vaddr;
	int ret;

	mutex_lock(&omap_obj->lock);

	if (!omap_obj->vaddr) {
		ret = omap_gem_attach_pages(obj);
		if (ret) {
			vaddr = ERR_PTR(ret);
			goto unlock;
		}

		omap_obj->vaddr = vmap(omap_obj->pages, obj->size >> PAGE_SHIFT,
				VM_MAP, pgprot_writecombine(PAGE_KERNEL));
	}

	vaddr = omap_obj->vaddr;

unlock:
	mutex_unlock(&omap_obj->lock);
	return vaddr;
}
#endif

/* -----------------------------------------------------------------------------
 * Power Management
 */

#ifdef CONFIG_PM
/* re-pin objects in DMM in resume path: */
int omap_gem_resume(struct drm_device *dev)
{
	struct omap_drm_private *priv = dev->dev_private;
	struct omap_gem_object *omap_obj;
	int ret = 0;

	mutex_lock(&priv->list_lock);
	list_for_each_entry(omap_obj, &priv->obj_list, mm_list) {
		if (omap_obj->block) {
			struct drm_gem_object *obj = &omap_obj->base;
			u32 npages = obj->size >> PAGE_SHIFT;

			WARN_ON(!omap_obj->pages);  /* this can't happen */
			ret = tiler_pin(omap_obj->block,
					omap_obj->pages, npages,
					omap_obj->roll, true);
			if (ret) {
				dev_err(dev->dev, "could not repin: %d\n", ret);
				goto done;
			}
		}
	}

done:
	mutex_unlock(&priv->list_lock);
	return ret;
}
#endif

/* -----------------------------------------------------------------------------
 * DebugFS
 */

#ifdef CONFIG_DEBUG_FS
void omap_gem_describe(struct drm_gem_object *obj, struct seq_file *m)
{
	struct omap_gem_object *omap_obj = to_omap_bo(obj);
	u64 off;

	off = drm_vma_node_start(&obj->vma_node);

	mutex_lock(&omap_obj->lock);

	seq_printf(m, "%08x: %2d (%2d) %08llx %pad (%2d) %p %4d",
			omap_obj->flags, obj->name, kref_read(&obj->refcount),
			off, &omap_obj->dma_addr,
			refcount_read(&omap_obj->pin_cnt),
			omap_obj->vaddr, omap_obj->roll);

	if (omap_obj->flags & OMAP_BO_TILED_MASK) {
		seq_printf(m, " %dx%d", omap_obj->width, omap_obj->height);
		if (omap_obj->block) {
			struct tcm_area *area = &omap_obj->block->area;
			seq_printf(m, " (%dx%d, %dx%d)",
					area->p0.x, area->p0.y,
					area->p1.x, area->p1.y);
		}
	} else {
		seq_printf(m, " %zu", obj->size);
	}

	mutex_unlock(&omap_obj->lock);

	seq_printf(m, "\n");
}

void omap_gem_describe_objects(struct list_head *list, struct seq_file *m)
{
	struct omap_gem_object *omap_obj;
	int count = 0;
	size_t size = 0;

	list_for_each_entry(omap_obj, list, mm_list) {
		struct drm_gem_object *obj = &omap_obj->base;
		seq_printf(m, "   ");
		omap_gem_describe(obj, m);
		count++;
		size += obj->size;
	}

	seq_printf(m, "Total %d objects, %zu bytes\n", count, size);
}
#endif

/* -----------------------------------------------------------------------------
 * Constructor & Destructor
 */

static void omap_gem_free_object(struct drm_gem_object *obj)
{
	struct drm_device *dev = obj->dev;
	struct omap_drm_private *priv = dev->dev_private;
	struct omap_gem_object *omap_obj = to_omap_bo(obj);

	omap_gem_evict(obj);

	mutex_lock(&priv->list_lock);
	list_del(&omap_obj->mm_list);
	mutex_unlock(&priv->list_lock);

	/*
	 * We own the sole reference to the object at this point, but to keep
	 * lockdep happy, we must still take the omap_obj_lock to call
	 * omap_gem_detach_pages(). This should hardly make any difference as
	 * there can't be any lock contention.
	 */
	mutex_lock(&omap_obj->lock);

	/* The object should not be pinned. */
	WARN_ON(refcount_read(&omap_obj->pin_cnt) > 0);

	if (omap_obj->pages) {
		if (omap_obj->flags & OMAP_BO_MEM_DMABUF)
			kfree(omap_obj->pages);
		else
			omap_gem_detach_pages(obj);
	}

	if (omap_obj->flags & OMAP_BO_MEM_DMA_API) {
		dma_free_wc(dev->dev, obj->size, omap_obj->vaddr,
			    omap_obj->dma_addr);
	} else if (omap_obj->vaddr) {
		vunmap(omap_obj->vaddr);
	} else if (obj->import_attach) {
		drm_prime_gem_destroy(obj, omap_obj->sgt);
	}

	mutex_unlock(&omap_obj->lock);

	drm_gem_object_release(obj);

	mutex_destroy(&omap_obj->lock);

	kfree(omap_obj);
}

static bool omap_gem_validate_flags(struct drm_device *dev, u32 flags)
{
	struct omap_drm_private *priv = dev->dev_private;

	switch (flags & OMAP_BO_CACHE_MASK) {
	case OMAP_BO_CACHED:
	case OMAP_BO_WC:
	case OMAP_BO_CACHE_MASK:
		break;

	default:
		return false;
	}

	if (flags & OMAP_BO_TILED_MASK) {
		if (!priv->usergart)
			return false;

		switch (flags & OMAP_BO_TILED_MASK) {
		case OMAP_BO_TILED_8:
		case OMAP_BO_TILED_16:
		case OMAP_BO_TILED_32:
			break;

		default:
			return false;
		}
	}

	return true;
}

static const struct vm_operations_struct omap_gem_vm_ops = {
	.fault = omap_gem_fault,
	.open = drm_gem_vm_open,
	.close = drm_gem_vm_close,
};

static const struct drm_gem_object_funcs omap_gem_object_funcs = {
	.free = omap_gem_free_object,
	.export = omap_gem_prime_export,
	.mmap = omap_gem_object_mmap,
	.vm_ops = &omap_gem_vm_ops,
};

/* GEM buffer object constructor */
struct drm_gem_object *omap_gem_new(struct drm_device *dev,
		union omap_gem_size gsize, u32 flags)
{
	struct omap_drm_private *priv = dev->dev_private;
	struct omap_gem_object *omap_obj;
	struct drm_gem_object *obj;
	struct address_space *mapping;
	size_t size;
	int ret;

	if (!omap_gem_validate_flags(dev, flags))
		return NULL;

	/* Validate the flags and compute the memory and cache flags. */
	if (flags & OMAP_BO_TILED_MASK) {
		/*
		 * Tiled buffers are always shmem paged backed. When they are
		 * scanned out, they are remapped into DMM/TILER.
		 */
		flags |= OMAP_BO_MEM_SHMEM;

		/*
		 * Currently don't allow cached buffers. There is some caching
		 * stuff that needs to be handled better.
		 */
		flags &= ~(OMAP_BO_CACHED|OMAP_BO_WC|OMAP_BO_UNCACHED);
		flags |= tiler_get_cpu_cache_flags();
	} else if ((flags & OMAP_BO_SCANOUT) && !priv->has_dmm) {
		/*
		 * If we don't have DMM, we must allocate scanout buffers
		 * from contiguous DMA memory.
		 */
		flags |= OMAP_BO_MEM_DMA_API;
	} else if (!(flags & OMAP_BO_MEM_DMABUF)) {
		/*
		 * All other buffers not backed by dma_buf are shmem-backed.
		 */
		flags |= OMAP_BO_MEM_SHMEM;
	}

	/* Allocate the initialize the OMAP GEM object. */
	omap_obj = kzalloc(sizeof(*omap_obj), GFP_KERNEL);
	if (!omap_obj)
		return NULL;

	obj = &omap_obj->base;
	omap_obj->flags = flags;
	mutex_init(&omap_obj->lock);

	if (flags & OMAP_BO_TILED_MASK) {
		/*
		 * For tiled buffers align dimensions to slot boundaries and
		 * calculate size based on aligned dimensions.
		 */
		tiler_align(gem2fmt(flags), &gsize.tiled.width,
			    &gsize.tiled.height);

		size = tiler_size(gem2fmt(flags), gsize.tiled.width,
				  gsize.tiled.height);

		omap_obj->width = gsize.tiled.width;
		omap_obj->height = gsize.tiled.height;
	} else {
		size = PAGE_ALIGN(gsize.bytes);
	}

	obj->funcs = &omap_gem_object_funcs;

	/* Initialize the GEM object. */
	if (!(flags & OMAP_BO_MEM_SHMEM)) {
		drm_gem_private_object_init(dev, obj, size);
	} else {
		ret = drm_gem_object_init(dev, obj, size);
		if (ret)
			goto err_free;

		mapping = obj->filp->f_mapping;
		mapping_set_gfp_mask(mapping, GFP_USER | __GFP_DMA32);
	}

	/* Allocate memory if needed. */
	if (flags & OMAP_BO_MEM_DMA_API) {
		omap_obj->vaddr = dma_alloc_wc(dev->dev, size,
					       &omap_obj->dma_addr,
					       GFP_KERNEL);
		if (!omap_obj->vaddr)
			goto err_release;
	}

	mutex_lock(&priv->list_lock);
	list_add(&omap_obj->mm_list, &priv->obj_list);
	mutex_unlock(&priv->list_lock);

	return obj;

err_release:
	drm_gem_object_release(obj);
err_free:
	kfree(omap_obj);
	return NULL;
}

struct drm_gem_object *omap_gem_new_dmabuf(struct drm_device *dev, size_t size,
					   struct sg_table *sgt)
{
	struct omap_drm_private *priv = dev->dev_private;
	struct omap_gem_object *omap_obj;
	struct drm_gem_object *obj;
	union omap_gem_size gsize;

	/* Without a DMM only physically contiguous buffers can be supported. */
	if (!omap_gem_sgt_is_contiguous(sgt, size) && !priv->has_dmm)
		return ERR_PTR(-EINVAL);

	gsize.bytes = PAGE_ALIGN(size);
	obj = omap_gem_new(dev, gsize, OMAP_BO_MEM_DMABUF | OMAP_BO_WC);
	if (!obj)
		return ERR_PTR(-ENOMEM);

	omap_obj = to_omap_bo(obj);

	omap_obj->sgt = sgt;

	if (omap_gem_sgt_is_contiguous(sgt, size)) {
		omap_obj->dma_addr = sg_dma_address(sgt->sgl);
	} else {
		/* Create pages list from sgt */
		struct page **pages;
		unsigned int npages;
		unsigned int ret;

		npages = DIV_ROUND_UP(size, PAGE_SIZE);
		pages = kcalloc(npages, sizeof(*pages), GFP_KERNEL);
		if (!pages) {
			omap_gem_free_object(obj);
			return ERR_PTR(-ENOMEM);
		}

		omap_obj->pages = pages;
		ret = drm_prime_sg_to_page_array(sgt, pages, npages);
		if (ret) {
			omap_gem_free_object(obj);
			return ERR_PTR(-ENOMEM);
		}
	}

	return obj;
}

/* convenience method to construct a GEM buffer object, and userspace handle */
int omap_gem_new_handle(struct drm_device *dev, struct drm_file *file,
		union omap_gem_size gsize, u32 flags, u32 *handle)
{
	struct drm_gem_object *obj;
	int ret;

	obj = omap_gem_new(dev, gsize, flags);
	if (!obj)
		return -ENOMEM;

	ret = drm_gem_handle_create(file, obj, handle);
	if (ret) {
		omap_gem_free_object(obj);
		return ret;
	}

	/* drop reference from allocate - handle holds it now */
	drm_gem_object_put(obj);

	return 0;
}

/* -----------------------------------------------------------------------------
 * Init & Cleanup
 */

/* If DMM is used, we need to set some stuff up.. */
void omap_gem_init(struct drm_device *dev)
{
	struct omap_drm_private *priv = dev->dev_private;
	struct omap_drm_usergart *usergart;
	const enum tiler_fmt fmts[] = {
			TILFMT_8BIT, TILFMT_16BIT, TILFMT_32BIT
	};
	int i, j;

	if (!dmm_is_available()) {
		/* DMM only supported on OMAP4 and later, so this isn't fatal */
		dev_warn(dev->dev, "DMM not available, disable DMM support\n");
		return;
	}

	usergart = kcalloc(3, sizeof(*usergart), GFP_KERNEL);
	if (!usergart)
		return;

	/* reserve 4k aligned/wide regions for userspace mappings: */
	for (i = 0; i < ARRAY_SIZE(fmts); i++) {
		u16 h = 1, w = PAGE_SIZE >> i;

		tiler_align(fmts[i], &w, &h);
		/* note: since each region is 1 4kb page wide, and minimum
		 * number of rows, the height ends up being the same as the
		 * # of pages in the region
		 */
		usergart[i].height = h;
		usergart[i].height_shift = ilog2(h);
		usergart[i].stride_pfn = tiler_stride(fmts[i], 0) >> PAGE_SHIFT;
		usergart[i].slot_shift = ilog2((PAGE_SIZE / h) >> i);
		for (j = 0; j < NUM_USERGART_ENTRIES; j++) {
			struct omap_drm_usergart_entry *entry;
			struct tiler_block *block;

			entry = &usergart[i].entry[j];
			block = tiler_reserve_2d(fmts[i], w, h, PAGE_SIZE);
			if (IS_ERR(block)) {
				dev_err(dev->dev,
						"reserve failed: %d, %d, %ld\n",
						i, j, PTR_ERR(block));
				return;
			}
			entry->dma_addr = tiler_ssptr(block);
			entry->block = block;

			DBG("%d:%d: %dx%d: dma_addr=%pad stride=%d", i, j, w, h,
					&entry->dma_addr,
					usergart[i].stride_pfn << PAGE_SHIFT);
		}
	}

	priv->usergart = usergart;
	priv->has_dmm = true;
}

void omap_gem_deinit(struct drm_device *dev)
{
	struct omap_drm_private *priv = dev->dev_private;

	/* I believe we can rely on there being no more outstanding GEM
	 * objects which could depend on usergart/dmm at this point.
	 */
	kfree(priv->usergart);
}