staging: add omapdrm DRM/KMS driver for TI OMAP platforms

A DRM display driver for TI OMAP platform.  Similar to omapfb (fbdev)
and omap_vout (v4l2 display) drivers in the past, this driver uses the
DSS2 driver to access the display hardware, including support for
HDMI, DVI, and various types of LCD panels.  And it implements GEM
support for buffer allocation (for KMS as well as offscreen buffers
used by the xf86-video-omap userspace xorg driver).

The driver maps CRTCs to overlays, encoders to overlay-managers, and
connectors to dssdev's.  Note that this arrangement might change slightly
when support for drm_plane overlays is added.

For GEM support, non-scanout buffers are using the shmem backed pages
provided by GEM core (In drm_gem_object_init()).  In the case of scanout
buffers, which need to be physically contiguous, those are allocated
with CMA and use drm_gem_private_object_init().

See userspace xorg driver:
git://github.com/robclark/xf86-video-omap.git

Refer to this link for CMA (Continuous Memory Allocator):
http://lkml.org/lkml/2011/8/19/302

Links to previous versions of the patch:
v1: http://lwn.net/Articles/458137/
v2: http://patches.linaro.org/4156/
v3: http://patches.linaro.org/4688/
v4: http://patches.linaro.org/4791/

History:

v5: move headers from include/drm at Greg KH's request, minor rebasing
    on 3.2-rc1, pull in private copies of drm_gem_{get,put}_pages()
    because "drm/gem: add functions to get/put pages" patch is not
    merged yet
v4: bit of rework of encoder/connector _dpms() code, modeset_init()
    rework to not use nested functions, update TODO.txt
v3: minor cleanups, improved error handling for dev_load(), some minor
    API changes that will be needed later for tiled buffer support
v2: replace omap_vram with CMA for scanout buffer allocation, remove
    unneeded functions, use dma_addr_t for physical addresses, error
    handling cleanup, refactor attach/detach pages into common drm
    functions, split non-userspace-facing API into omap_priv.h, remove
    plugin API

v1: original

Signed-off-by: Rob Clark <rob@ti.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 774 insertions, 0 deletions

diff --git a/drivers/staging/omapdrm/omap_gem.c b/drivers/staging/omapdrm/omap_gem.c
new file mode 100644
index 0000000..bc1709c
--- /dev/null
+++ b/drivers/staging/omapdrm/omap_gem.c
@@ -0,0 +1,774 @@
+/*
+ * drivers/staging/omapdrm/omap_gem.c
+ *
+ * Copyright (C) 2011 Texas Instruments
+ * Author: Rob Clark <rob.clark@linaro.org>
+ *
+ * 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, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#include <linux/spinlock.h>
+#include <linux/shmem_fs.h>
+
+#include "omap_drv.h"
+
+/* remove these once drm core helpers are merged */
+struct page ** _drm_gem_get_pages(struct drm_gem_object *obj, gfp_t gfpmask);
+void _drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
+		bool dirty, bool accessed);
+
+/*
+ * GEM buffer object implementation.
+ */
+
+#define to_omap_bo(x) container_of(x, struct omap_gem_object, base)
+
+/* note: we use upper 8 bits of flags for driver-internal flags: */
+#define OMAP_BO_DMA			0x01000000	/* actually is physically contiguous */
+#define OMAP_BO_EXT_SYNC	0x02000000	/* externally allocated sync object */
+#define OMAP_BO_EXT_MEM		0x04000000	/* externally allocated memory */
+
+
+struct omap_gem_object {
+	struct drm_gem_object base;
+
+	uint32_t flags;
+
+	/**
+	 * If buffer is allocated physically contiguous, the OMAP_BO_DMA flag
+	 * is set and the paddr is valid.
+	 *
+	 * Note that OMAP_BO_SCANOUT is a hint from userspace that DMA capable
+	 * buffer is requested, but doesn't mean that it is.  Use the
+	 * OMAP_BO_DMA flag to determine if the buffer has a DMA capable
+	 * physical address.
+	 */
+	dma_addr_t paddr;
+
+	/**
+	 * Array of backing pages, if allocated.  Note that pages are never
+	 * allocated for buffers originally allocated from contiguous memory
+	 */
+	struct page **pages;
+
+	/**
+	 * Virtual address, if mapped.
+	 */
+	void *vaddr;
+
+	/**
+	 * sync-object allocated on demand (if needed)
+	 *
+	 * Per-buffer sync-object for tracking pending and completed hw/dma
+	 * read and write operations.  The layout in memory is dictated by
+	 * the SGX firmware, which uses this information to stall the command
+	 * stream if a surface is not ready yet.
+	 *
+	 * Note that when buffer is used by SGX, the sync-object needs to be
+	 * allocated from a special heap of sync-objects.  This way many sync
+	 * objects can be packed in a page, and not waste GPU virtual address
+	 * space.  Because of this we have to have a omap_gem_set_sync_object()
+	 * API to allow replacement of the syncobj after it has (potentially)
+	 * already been allocated.  A bit ugly but I haven't thought of a
+	 * better alternative.
+	 */
+	struct {
+		uint32_t write_pending;
+		uint32_t write_complete;
+		uint32_t read_pending;
+		uint32_t read_complete;
+	} *sync;
+};
+
+/* GEM objects can either be allocated from contiguous memory (in which
+ * case obj->filp==NULL), or w/ shmem backing (obj->filp!=NULL).  But non
+ * contiguous buffers can be remapped in TILER/DMM if they need to be
+ * contiguous... but we don't do this all the time to reduce pressure
+ * on TILER/DMM space when we know at allocation time that the buffer
+ * will need to be scanned out.
+ */
+static inline bool is_shmem(struct drm_gem_object *obj)
+{
+	return obj->filp != NULL;
+}
+
+static int get_pages(struct drm_gem_object *obj, struct page ***pages);
+
+static DEFINE_SPINLOCK(sync_lock);
+
+/** ensure backing pages are allocated */
+static int omap_gem_attach_pages(struct drm_gem_object *obj)
+{
+	struct omap_gem_object *omap_obj = to_omap_bo(obj);
+	struct page **pages;
+
+	WARN_ON(omap_obj->pages);
+
+	/* TODO: __GFP_DMA32 .. but somehow GFP_HIGHMEM is coming from the
+	 * mapping_gfp_mask(mapping) which conflicts w/ GFP_DMA32.. probably
+	 * we actually want CMA memory for it all anyways..
+	 */
+	pages = _drm_gem_get_pages(obj, GFP_KERNEL);
+	if (IS_ERR(pages)) {
+		dev_err(obj->dev->dev, "could not get pages: %ld\n", PTR_ERR(pages));
+		return PTR_ERR(pages);
+	}
+
+	omap_obj->pages = pages;
+	return 0;
+}
+
+/** release backing pages */
+static void omap_gem_detach_pages(struct drm_gem_object *obj)
+{
+	struct omap_gem_object *omap_obj = to_omap_bo(obj);
+	_drm_gem_put_pages(obj, omap_obj->pages, true, false);
+	omap_obj->pages = NULL;
+}
+
+/** get mmap offset */
+uint64_t omap_gem_mmap_offset(struct drm_gem_object *obj)
+{
+	if (!obj->map_list.map) {
+		/* Make it mmapable */
+		int ret = drm_gem_create_mmap_offset(obj);
+		if (ret) {
+			dev_err(obj->dev->dev, "could not allocate mmap offset");
+			return 0;
+		}
+	}
+
+	return (uint64_t)obj->map_list.hash.key << PAGE_SHIFT;
+}
+
+/**
+ * omap_gem_fault		-	pagefault handler for GEM objects
+ * @vma: the VMA of the GEM object
+ * @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.
+ */
+int omap_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+	struct drm_gem_object *obj = vma->vm_private_data;
+	struct omap_gem_object *omap_obj = to_omap_bo(obj);
+	struct drm_device *dev = obj->dev;
+	struct page **pages;
+	unsigned long pfn;
+	pgoff_t pgoff;
+	int ret;
+
+	/* Make sure we don't parallel update on a fault, nor move or remove
+	 * something from beneath our feet
+	 */
+	mutex_lock(&dev->struct_mutex);
+
+	/* if a shmem backed object, make sure we have pages attached now */
+	ret = get_pages(obj, &pages);
+	if (ret) {
+		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()?
+	 */
+
+	/* We don't use vmf->pgoff since that has the fake offset: */
+	pgoff = ((unsigned long)vmf->virtual_address -
+			vma->vm_start) >> PAGE_SHIFT;
+
+	if (omap_obj->pages) {
+		pfn = page_to_pfn(omap_obj->pages[pgoff]);
+	} else {
+		BUG_ON(!(omap_obj->flags & OMAP_BO_DMA));
+		pfn = (omap_obj->paddr >> PAGE_SHIFT) + pgoff;
+	}
+
+	VERB("Inserting %p pfn %lx, pa %lx", vmf->virtual_address,
+			pfn, pfn << PAGE_SHIFT);
+
+	ret = vm_insert_mixed(vma, (unsigned long)vmf->virtual_address, pfn);
+
+fail:
+	mutex_unlock(&dev->struct_mutex);
+	switch (ret) {
+	case 0:
+	case -ERESTARTSYS:
+	case -EINTR:
+		return VM_FAULT_NOPAGE;
+	case -ENOMEM:
+		return VM_FAULT_OOM;
+	default:
+		return VM_FAULT_SIGBUS;
+	}
+}
+
+/** We override mainly to fix up some of the vm mapping flags.. */
+int omap_gem_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct omap_gem_object *omap_obj;
+	int ret;
+
+	ret = drm_gem_mmap(filp, vma);
+	if (ret) {
+		DBG("mmap failed: %d", ret);
+		return ret;
+	}
+
+	/* after drm_gem_mmap(), it is safe to access the obj */
+	omap_obj = to_omap_bo(vma->vm_private_data);
+
+	vma->vm_flags &= ~VM_PFNMAP;
+	vma->vm_flags |= 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 {
+		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+	}
+
+	return ret;
+}
+
+/**
+ * omap_gem_dumb_create	-	create a dumb buffer
+ * @drm_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;
+
+	/* in case someone tries to feed us a completely bogus stride: */
+	args->pitch = align_pitch(args->pitch, args->width, args->bpp);
+	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_destroy	-	destroy a dumb buffer
+ * @file: client file
+ * @dev: our DRM device
+ * @handle: the object handle
+ *
+ * Destroy a handle that was created via omap_gem_dumb_create.
+ */
+int omap_gem_dumb_destroy(struct drm_file *file, struct drm_device *dev,
+		uint32_t handle)
+{
+	/* No special work needed, drop the reference and see what falls out */
+	return drm_gem_handle_delete(file, handle);
+}
+
+/**
+ * omap_gem_dumb_map	-	buffer mapping for dumb interface
+ * @file: our drm client file
+ * @dev: drm device
+ * @handle: GEM handle to the object (from dumb_create)
+ *
+ * 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,
+		uint32_t handle, uint64_t *offset)
+{
+	struct drm_gem_object *obj;
+	int ret = 0;
+
+	mutex_lock(&dev->struct_mutex);
+
+	/* GEM does all our handle to object mapping */
+	obj = drm_gem_object_lookup(dev, file, handle);
+	if (obj == NULL) {
+		ret = -ENOENT;
+		goto fail;
+	}
+
+	*offset = omap_gem_mmap_offset(obj);
+
+	drm_gem_object_unreference_unlocked(obj);
+
+fail:
+	mutex_unlock(&dev->struct_mutex);
+	return ret;
+}
+
+/* Get physical address for DMA.. if 'remap' is true, and the buffer is not
+ * already contiguous, remap it to pin in physically contiguous memory.. (ie.
+ * map in TILER)
+ */
+int omap_gem_get_paddr(struct drm_gem_object *obj,
+		dma_addr_t *paddr, bool remap)
+{
+	struct omap_gem_object *omap_obj = to_omap_bo(obj);
+	int ret = 0;
+
+	if (is_shmem(obj)) {
+		/* TODO: remap to TILER */
+		return -ENOMEM;
+	}
+
+	*paddr = omap_obj->paddr;
+
+	return ret;
+}
+
+/* Release physical address, when DMA is no longer being performed.. this
+ * could potentially unpin and unmap buffers from TILER
+ */
+int omap_gem_put_paddr(struct drm_gem_object *obj)
+{
+	/* do something here when remap to TILER is used.. */
+	return 0;
+}
+
+/* acquire pages when needed (for example, for DMA where physically
+ * contiguous buffer is not required
+ */
+static int get_pages(struct drm_gem_object *obj, struct page ***pages)
+{
+	struct omap_gem_object *omap_obj = to_omap_bo(obj);
+	int ret = 0;
+
+	if (is_shmem(obj) && !omap_obj->pages) {
+		ret = omap_gem_attach_pages(obj);
+		if (ret) {
+			dev_err(obj->dev->dev, "could not attach pages\n");
+			return ret;
+		}
+	}
+
+	/* TODO: even phys-contig.. we should have a list of pages? */
+	*pages = omap_obj->pages;
+
+	return 0;
+}
+
+int omap_gem_get_pages(struct drm_gem_object *obj, struct page ***pages)
+{
+	int ret;
+	mutex_lock(&obj->dev->struct_mutex);
+	ret = get_pages(obj, pages);
+	mutex_unlock(&obj->dev->struct_mutex);
+	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;
+}
+
+/* Get kernel virtual address for CPU access.. only buffers that are
+ * allocated contiguously have a kernel virtual address, so 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);
+	return omap_obj->vaddr;
+}
+
+/* Buffer Synchronization:
+ */
+
+struct omap_gem_sync_waiter {
+	struct list_head list;
+	struct omap_gem_object *omap_obj;
+	enum omap_gem_op op;
+	uint32_t read_target, write_target;
+	/* notify called w/ sync_lock held */
+	void (*notify)(void *arg);
+	void *arg;
+};
+
+/* list of omap_gem_sync_waiter.. the notify fxn gets called back when
+ * the read and/or write target count is achieved which can call a user
+ * callback (ex. to kick 3d and/or 2d), wakeup blocked task (prep for
+ * cpu access), etc.
+ */
+static LIST_HEAD(waiters);
+
+static inline bool is_waiting(struct omap_gem_sync_waiter *waiter)
+{
+	struct omap_gem_object *omap_obj = waiter->omap_obj;
+	if ((waiter->op & OMAP_GEM_READ) &&
+			(omap_obj->sync->read_complete < waiter->read_target))
+		return true;
+	if ((waiter->op & OMAP_GEM_WRITE) &&
+			(omap_obj->sync->write_complete < waiter->write_target))
+		return true;
+	return false;
+}
+
+/* macro for sync debug.. */
+#define SYNCDBG 0
+#define SYNC(fmt, ...) do { if (SYNCDBG) \
+		printk(KERN_ERR "%s:%d: "fmt"\n", \
+				__func__, __LINE__, ##__VA_ARGS__); \
+	} while (0)
+
+
+static void sync_op_update(void)
+{
+	struct omap_gem_sync_waiter *waiter, *n;
+	list_for_each_entry_safe(waiter, n, &waiters, list) {
+		if (!is_waiting(waiter)) {
+			list_del(&waiter->list);
+			SYNC("notify: %p", waiter);
+			waiter->notify(waiter->arg);
+			kfree(waiter);
+		}
+	}
+}
+
+static inline int sync_op(struct drm_gem_object *obj,
+		enum omap_gem_op op, bool start)
+{
+	struct omap_gem_object *omap_obj = to_omap_bo(obj);
+	int ret = 0;
+
+	spin_lock(&sync_lock);
+
+	if (!omap_obj->sync) {
+		omap_obj->sync = kzalloc(sizeof(*omap_obj->sync), GFP_ATOMIC);
+		if (!omap_obj->sync) {
+			ret = -ENOMEM;
+			goto unlock;
+		}
+	}
+
+	if (start) {
+		if (op & OMAP_GEM_READ)
+			omap_obj->sync->read_pending++;
+		if (op & OMAP_GEM_WRITE)
+			omap_obj->sync->write_pending++;
+	} else {
+		if (op & OMAP_GEM_READ)
+			omap_obj->sync->read_complete++;
+		if (op & OMAP_GEM_WRITE)
+			omap_obj->sync->write_complete++;
+		sync_op_update();
+	}
+
+unlock:
+	spin_unlock(&sync_lock);
+
+	return ret;
+}
+
+/* it is a bit lame to handle updates in this sort of polling way, but
+ * in case of PVR, the GPU can directly update read/write complete
+ * values, and not really tell us which ones it updated.. this also
+ * means that sync_lock is not quite sufficient.  So we'll need to
+ * do something a bit better when it comes time to add support for
+ * separate 2d hw..
+ */
+void omap_gem_op_update(void)
+{
+	spin_lock(&sync_lock);
+	sync_op_update();
+	spin_unlock(&sync_lock);
+}
+
+/* mark the start of read and/or write operation */
+int omap_gem_op_start(struct drm_gem_object *obj, enum omap_gem_op op)
+{
+	return sync_op(obj, op, true);
+}
+
+int omap_gem_op_finish(struct drm_gem_object *obj, enum omap_gem_op op)
+{
+	return sync_op(obj, op, false);
+}
+
+static DECLARE_WAIT_QUEUE_HEAD(sync_event);
+
+static void sync_notify(void *arg)
+{
+	struct task_struct **waiter_task = arg;
+	*waiter_task = NULL;
+	wake_up_all(&sync_event);
+}
+
+int omap_gem_op_sync(struct drm_gem_object *obj, enum omap_gem_op op)
+{
+	struct omap_gem_object *omap_obj = to_omap_bo(obj);
+	int ret = 0;
+	if (omap_obj->sync) {
+		struct task_struct *waiter_task = current;
+		struct omap_gem_sync_waiter *waiter =
+				kzalloc(sizeof(*waiter), GFP_KERNEL);
+
+		if (!waiter) {
+			return -ENOMEM;
+		}
+
+		waiter->omap_obj = omap_obj;
+		waiter->op = op;
+		waiter->read_target = omap_obj->sync->read_pending;
+		waiter->write_target = omap_obj->sync->write_pending;
+		waiter->notify = sync_notify;
+		waiter->arg = &waiter_task;
+
+		spin_lock(&sync_lock);
+		if (is_waiting(waiter)) {
+			SYNC("waited: %p", waiter);
+			list_add_tail(&waiter->list, &waiters);
+			spin_unlock(&sync_lock);
+			ret = wait_event_interruptible(sync_event,
+					(waiter_task == NULL));
+			spin_lock(&sync_lock);
+			if (waiter_task) {
+				SYNC("interrupted: %p", waiter);
+				/* we were interrupted */
+				list_del(&waiter->list);
+				waiter_task = NULL;
+			} else {
+				/* freed in sync_op_update() */
+				waiter = NULL;
+			}
+		}
+		spin_unlock(&sync_lock);
+
+		if (waiter) {
+			kfree(waiter);
+		}
+	}
+	return ret;
+}
+
+/* call fxn(arg), either synchronously or asynchronously if the op
+ * is currently blocked..  fxn() can be called from any context
+ *
+ * (TODO for now fxn is called back from whichever context calls
+ * omap_gem_op_update().. but this could be better defined later
+ * if needed)
+ *
+ * TODO more code in common w/ _sync()..
+ */
+int omap_gem_op_async(struct drm_gem_object *obj, enum omap_gem_op op,
+		void (*fxn)(void *arg), void *arg)
+{
+	struct omap_gem_object *omap_obj = to_omap_bo(obj);
+	if (omap_obj->sync) {
+		struct omap_gem_sync_waiter *waiter =
+				kzalloc(sizeof(*waiter), GFP_ATOMIC);
+
+		if (!waiter) {
+			return -ENOMEM;
+		}
+
+		waiter->omap_obj = omap_obj;
+		waiter->op = op;
+		waiter->read_target = omap_obj->sync->read_pending;
+		waiter->write_target = omap_obj->sync->write_pending;
+		waiter->notify = fxn;
+		waiter->arg = arg;
+
+		spin_lock(&sync_lock);
+		if (is_waiting(waiter)) {
+			SYNC("waited: %p", waiter);
+			list_add_tail(&waiter->list, &waiters);
+			spin_unlock(&sync_lock);
+			return 0;
+		}
+
+		spin_unlock(&sync_lock);
+	}
+
+	/* no waiting.. */
+	fxn(arg);
+
+	return 0;
+}
+
+/* special API so PVR can update the buffer to use a sync-object allocated
+ * from it's sync-obj heap.  Only used for a newly allocated (from PVR's
+ * perspective) sync-object, so we overwrite the new syncobj w/ values
+ * from the already allocated syncobj (if there is one)
+ */
+int omap_gem_set_sync_object(struct drm_gem_object *obj, void *syncobj)
+{
+	struct omap_gem_object *omap_obj = to_omap_bo(obj);
+	int ret = 0;
+
+	spin_lock(&sync_lock);
+
+	if ((omap_obj->flags & OMAP_BO_EXT_SYNC) && !syncobj) {
+		/* clearing a previously set syncobj */
+		syncobj = kzalloc(sizeof(*omap_obj->sync), GFP_ATOMIC);
+		if (!syncobj) {
+			ret = -ENOMEM;
+			goto unlock;
+		}
+		memcpy(syncobj, omap_obj->sync, sizeof(*omap_obj->sync));
+		omap_obj->flags &= ~OMAP_BO_EXT_SYNC;
+		omap_obj->sync = syncobj;
+	} else if (syncobj && !(omap_obj->flags & OMAP_BO_EXT_SYNC)) {
+		/* replacing an existing syncobj */
+		if (omap_obj->sync) {
+			memcpy(syncobj, omap_obj->sync, sizeof(*omap_obj->sync));
+			kfree(omap_obj->sync);
+		}
+		omap_obj->flags |= OMAP_BO_EXT_SYNC;
+		omap_obj->sync = syncobj;
+	}
+
+unlock:
+	spin_unlock(&sync_lock);
+	return ret;
+}
+
+int omap_gem_init_object(struct drm_gem_object *obj)
+{
+	return -EINVAL;          /* unused */
+}
+
+/* don't call directly.. called from GEM core when it is time to actually
+ * free the object..
+ */
+void omap_gem_free_object(struct drm_gem_object *obj)
+{
+	struct drm_device *dev = obj->dev;
+	struct omap_gem_object *omap_obj = to_omap_bo(obj);
+
+	if (obj->map_list.map) {
+		drm_gem_free_mmap_offset(obj);
+	}
+
+	/* don't free externally allocated backing memory */
+	if (!(omap_obj->flags & OMAP_BO_EXT_MEM)) {
+		if (omap_obj->pages) {
+			omap_gem_detach_pages(obj);
+		}
+		if (!is_shmem(obj)) {
+			dma_free_writecombine(dev->dev, obj->size,
+					omap_obj->vaddr, omap_obj->paddr);
+		}
+	}
+
+	/* don't free externally allocated syncobj */
+	if (!(omap_obj->flags & OMAP_BO_EXT_SYNC)) {
+		kfree(omap_obj->sync);
+	}
+
+	drm_gem_object_release(obj);
+
+	kfree(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, uint32_t flags, uint32_t *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) {
+		drm_gem_object_release(obj);
+		kfree(obj); /* TODO isn't there a dtor to call? just copying i915 */
+		return ret;
+	}
+
+	/* drop reference from allocate - handle holds it now */
+	drm_gem_object_unreference_unlocked(obj);
+
+	return 0;
+}
+
+/* GEM buffer object constructor */
+struct drm_gem_object *omap_gem_new(struct drm_device *dev,
+		union omap_gem_size gsize, uint32_t flags)
+{
+	struct omap_gem_object *omap_obj;
+	struct drm_gem_object *obj = NULL;
+	size_t size;
+	int ret;
+
+	if (flags & OMAP_BO_TILED) {
+		/* TODO: not implemented yet */
+		goto fail;
+	}
+
+	size = PAGE_ALIGN(gsize.bytes);
+
+	omap_obj = kzalloc(sizeof(*omap_obj), GFP_KERNEL);
+	if (!omap_obj) {
+		dev_err(dev->dev, "could not allocate GEM object\n");
+		goto fail;
+	}
+
+	obj = &omap_obj->base;
+
+	if (flags & OMAP_BO_SCANOUT) {
+		/* attempt to allocate contiguous memory */
+		omap_obj->vaddr =  dma_alloc_writecombine(dev->dev, size,
+				&omap_obj->paddr, GFP_KERNEL);
+		if (omap_obj->vaddr) {
+			flags |= OMAP_BO_DMA;
+		}
+	}
+
+	omap_obj->flags = flags;
+
+	if (flags & (OMAP_BO_DMA|OMAP_BO_EXT_MEM)) {
+		ret = drm_gem_private_object_init(dev, obj, size);
+	} else {
+		ret = drm_gem_object_init(dev, obj, size);
+	}
+
+	if (ret) {
+		goto fail;
+	}
+
+	return obj;
+
+fail:
+	if (obj) {
+		omap_gem_free_object(obj);
+	}
+	return NULL;
+}