drivers/gpu/drm/omapdrm/omap_fbdev.c - linux - Git at Google

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

 #include <linux/fb.h>

 #include <drm/drm_drv.h>
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_file.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_gem_framebuffer_helper.h>
 #include <drm/drm_util.h>

 #include "omap_drv.h"
 #include "omap_fbdev.h"

 MODULE_PARM_DESC(ywrap, "Enable ywrap scrolling (omap44xx and later, default 'y')");
 static bool ywrap_enabled = true;
 module_param_named(ywrap, ywrap_enabled, bool, 0644);

 /*
  * fbdev funcs, to implement legacy fbdev interface on top of drm driver
  */

 #define to_omap_fbdev(x) container_of(x, struct omap_fbdev, base)

 struct omap_fbdev {
 	struct drm_fb_helper base;
 	bool ywrap_enabled;

 	/* for deferred dmm roll when getting called in atomic ctx */
 	struct work_struct work;
 };

 static struct drm_fb_helper *get_fb(struct fb_info *fbi);

 static void pan_worker(struct work_struct *work)
 {
 	struct omap_fbdev *fbdev = container_of(work, struct omap_fbdev, work);
 	struct drm_fb_helper *helper = &fbdev->base;
 	struct fb_info *fbi = helper->info;
 	struct drm_gem_object *bo = drm_gem_fb_get_obj(helper->fb, 0);
 	int npages;

 	/* DMM roll shifts in 4K pages: */
 	npages = fbi->fix.line_length >> PAGE_SHIFT;
 	omap_gem_roll(bo, fbi->var.yoffset * npages);
 }

 FB_GEN_DEFAULT_DEFERRED_DMAMEM_OPS(omap_fbdev,
 				   drm_fb_helper_damage_range,
 				   drm_fb_helper_damage_area)

 static int omap_fbdev_pan_display(struct fb_var_screeninfo *var,
 		struct fb_info *fbi)
 {
 	struct drm_fb_helper *helper = get_fb(fbi);
 	struct omap_fbdev *fbdev = to_omap_fbdev(helper);

 	if (!helper)
 		goto fallback;

 	if (!fbdev->ywrap_enabled)
 		goto fallback;

 	if (drm_can_sleep()) {
 		pan_worker(&fbdev->work);
 	} else {
 		struct omap_drm_private *priv = helper->dev->dev_private;
 		queue_work(priv->wq, &fbdev->work);
 	}

 	return 0;

 fallback:
 	return drm_fb_helper_pan_display(var, fbi);
 }

 static int omap_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma)
 {
 	vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));

 	return fb_deferred_io_mmap(info, vma);
 }

 static void omap_fbdev_fb_destroy(struct fb_info *info)
 {
 	struct drm_fb_helper *helper = info->par;
 	struct drm_framebuffer *fb = helper->fb;
 	struct drm_gem_object *bo = drm_gem_fb_get_obj(fb, 0);
 	struct omap_fbdev *fbdev = to_omap_fbdev(helper);

 	DBG();

 	fb_deferred_io_cleanup(info);
 	drm_fb_helper_fini(helper);

 	omap_gem_unpin(bo);
 	drm_framebuffer_remove(fb);

 	drm_client_release(&helper->client);
 	drm_fb_helper_unprepare(helper);
 	kfree(fbdev);
 }

 /*
  * For now, we cannot use FB_DEFAULT_DEFERRED_OPS and fb_deferred_io_mmap()
  * because we use write-combine.
  */
 static const struct fb_ops omap_fb_ops = {
 	.owner = THIS_MODULE,
 	__FB_DEFAULT_DEFERRED_OPS_RDWR(omap_fbdev),
 	.fb_check_var	= drm_fb_helper_check_var,
 	.fb_set_par	= drm_fb_helper_set_par,
 	.fb_setcmap	= drm_fb_helper_setcmap,
 	.fb_blank	= drm_fb_helper_blank,
 	.fb_pan_display = omap_fbdev_pan_display,
 	__FB_DEFAULT_DEFERRED_OPS_DRAW(omap_fbdev),
 	.fb_ioctl	= drm_fb_helper_ioctl,
 	.fb_mmap	= omap_fbdev_fb_mmap,
 	.fb_destroy	= omap_fbdev_fb_destroy,
 };

 static int omap_fbdev_create(struct drm_fb_helper *helper,
 		struct drm_fb_helper_surface_size *sizes)
 {
 	struct omap_fbdev *fbdev = to_omap_fbdev(helper);
 	struct drm_device *dev = helper->dev;
 	struct omap_drm_private *priv = dev->dev_private;
 	struct drm_framebuffer *fb = NULL;
 	union omap_gem_size gsize;
 	struct fb_info *fbi = NULL;
 	struct drm_mode_fb_cmd2 mode_cmd = {0};
 	struct drm_gem_object *bo;
 	dma_addr_t dma_addr;
 	int ret;

 	sizes->surface_bpp = 32;
 	sizes->surface_depth = 24;

 	DBG("create fbdev: %dx%d@%d (%dx%d)", sizes->surface_width,
 			sizes->surface_height, sizes->surface_bpp,
 			sizes->fb_width, sizes->fb_height);

 	mode_cmd.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp,
 			sizes->surface_depth);

 	mode_cmd.width = sizes->surface_width;
 	mode_cmd.height = sizes->surface_height;

 	mode_cmd.pitches[0] =
 			DIV_ROUND_UP(mode_cmd.width * sizes->surface_bpp, 8);

 	fbdev->ywrap_enabled = priv->has_dmm && ywrap_enabled;
 	if (fbdev->ywrap_enabled) {
 		/* need to align pitch to page size if using DMM scrolling */
 		mode_cmd.pitches[0] = PAGE_ALIGN(mode_cmd.pitches[0]);
 	}

 	/* allocate backing bo */
 	gsize = (union omap_gem_size){
 		.bytes = PAGE_ALIGN(mode_cmd.pitches[0] * mode_cmd.height),
 	};
 	DBG("allocating %d bytes for fb %d", gsize.bytes, dev->primary->index);
 	bo = omap_gem_new(dev, gsize, OMAP_BO_SCANOUT | OMAP_BO_WC);
 	if (!bo) {
 		dev_err(dev->dev, "failed to allocate buffer object\n");
 		ret = -ENOMEM;
 		goto fail;
 	}

 	fb = omap_framebuffer_init(dev, &mode_cmd, &bo);
 	if (IS_ERR(fb)) {
 		dev_err(dev->dev, "failed to allocate fb\n");
 		/* note: if fb creation failed, we can't rely on fb destroy
 		 * to unref the bo:
 		 */
 		drm_gem_object_put(bo);
 		ret = PTR_ERR(fb);
 		goto fail;
 	}

 	/* note: this keeps the bo pinned.. which is perhaps not ideal,
 	 * but is needed as long as we use fb_mmap() to mmap to userspace
 	 * (since this happens using fix.smem_start).  Possibly we could
 	 * implement our own mmap using GEM mmap support to avoid this
 	 * (non-tiled buffer doesn't need to be pinned for fbcon to write
 	 * to it).  Then we just need to be sure that we are able to re-
 	 * pin it in case of an opps.
 	 */
 	ret = omap_gem_pin(bo, &dma_addr);
 	if (ret) {
 		dev_err(dev->dev, "could not pin framebuffer\n");
 		ret = -ENOMEM;
 		goto fail;
 	}

 	fbi = drm_fb_helper_alloc_info(helper);
 	if (IS_ERR(fbi)) {
 		dev_err(dev->dev, "failed to allocate fb info\n");
 		ret = PTR_ERR(fbi);
 		goto fail;
 	}

 	DBG("fbi=%p, dev=%p", fbi, dev);

 	helper->fb = fb;

 	fbi->fbops = &omap_fb_ops;

 	drm_fb_helper_fill_info(fbi, helper, sizes);

 	fbi->flags |= FBINFO_VIRTFB;
 	fbi->screen_buffer = omap_gem_vaddr(bo);
 	fbi->screen_size = bo->size;
 	fbi->fix.smem_start = dma_addr;
 	fbi->fix.smem_len = bo->size;

 	/* deferred I/O */
 	helper->fbdefio.delay = HZ / 20;
 	helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;

 	fbi->fbdefio = &helper->fbdefio;
 	ret = fb_deferred_io_init(fbi);
 	if (ret)
 		goto fail;

 	/* if we have DMM, then we can use it for scrolling by just
 	 * shuffling pages around in DMM rather than doing sw blit.
 	 */
 	if (fbdev->ywrap_enabled) {
 		DRM_INFO("Enabling DMM ywrap scrolling\n");
 		fbi->flags |= FBINFO_HWACCEL_YWRAP | FBINFO_READS_FAST;
 		fbi->fix.ywrapstep = 1;
 	}


 	DBG("par=%p, %dx%d", fbi->par, fbi->var.xres, fbi->var.yres);
 	DBG("allocated %dx%d fb", fb->width, fb->height);

 	return 0;

 fail:

 	if (ret) {
 		if (fb)
 			drm_framebuffer_remove(fb);
 	}

 	return ret;
 }

 static int omap_fbdev_dirty(struct drm_fb_helper *helper, struct drm_clip_rect *clip)
 {
 	if (!(clip->x1 < clip->x2 && clip->y1 < clip->y2))
 		return 0;

 	if (helper->fb->funcs->dirty)
 		return helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, clip, 1);

 	return 0;
 }

 static const struct drm_fb_helper_funcs omap_fb_helper_funcs = {
 	.fb_probe = omap_fbdev_create,
 	.fb_dirty = omap_fbdev_dirty,
 };

 static struct drm_fb_helper *get_fb(struct fb_info *fbi)
 {
 	if (!fbi || strcmp(fbi->fix.id, MODULE_NAME)) {
 		/* these are not the fb's you're looking for */
 		return NULL;
 	}
 	return fbi->par;
 }

 /*
  * struct drm_client
  */

 static void omap_fbdev_client_unregister(struct drm_client_dev *client)
 {
 	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);

 	if (fb_helper->info) {
 		drm_fb_helper_unregister_info(fb_helper);
 	} else {
 		drm_client_release(&fb_helper->client);
 		drm_fb_helper_unprepare(fb_helper);
 		kfree(fb_helper);
 	}
 }

 static int omap_fbdev_client_restore(struct drm_client_dev *client)
 {
 	drm_fb_helper_lastclose(client->dev);

 	return 0;
 }

 static int omap_fbdev_client_hotplug(struct drm_client_dev *client)
 {
 	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
 	struct drm_device *dev = client->dev;
 	int ret;

 	if (dev->fb_helper)
 		return drm_fb_helper_hotplug_event(dev->fb_helper);

 	ret = drm_fb_helper_init(dev, fb_helper);
 	if (ret)
 		goto err_drm_err;

 	ret = drm_fb_helper_initial_config(fb_helper);
 	if (ret)
 		goto err_drm_fb_helper_fini;

 	return 0;

 err_drm_fb_helper_fini:
 	drm_fb_helper_fini(fb_helper);
 err_drm_err:
 	drm_err(dev, "Failed to setup fbdev emulation (ret=%d)\n", ret);
 	return ret;
 }

 static const struct drm_client_funcs omap_fbdev_client_funcs = {
 	.owner		= THIS_MODULE,
 	.unregister	= omap_fbdev_client_unregister,
 	.restore	= omap_fbdev_client_restore,
 	.hotplug	= omap_fbdev_client_hotplug,
 };

 void omap_fbdev_setup(struct drm_device *dev)
 {
 	struct omap_fbdev *fbdev;
 	struct drm_fb_helper *helper;
 	int ret;

 	drm_WARN(dev, !dev->registered, "Device has not been registered.\n");
 	drm_WARN(dev, dev->fb_helper, "fb_helper is already set!\n");

 	fbdev = kzalloc(sizeof(*fbdev), GFP_KERNEL);
 	if (!fbdev)
 		return;
 	helper = &fbdev->base;

 	drm_fb_helper_prepare(dev, helper, 32, &omap_fb_helper_funcs);

 	ret = drm_client_init(dev, &helper->client, "fbdev", &omap_fbdev_client_funcs);
 	if (ret)
 		goto err_drm_client_init;

 	INIT_WORK(&fbdev->work, pan_worker);

 	drm_client_register(&helper->client);

 	return;

 err_drm_client_init:
 	drm_fb_helper_unprepare(helper);
 	kfree(fbdev);
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2011 Texas Instruments Incorporated - https://www.ti.com/
	* Author: Rob Clark <rob@ti.com>
	*/

	#include <linux/fb.h>

	#include <drm/drm_drv.h>
	#include <drm/drm_crtc_helper.h>
	#include <drm/drm_fb_helper.h>
	#include <drm/drm_file.h>
	#include <drm/drm_fourcc.h>
	#include <drm/drm_framebuffer.h>
	#include <drm/drm_gem_framebuffer_helper.h>
	#include <drm/drm_util.h>

	#include "omap_drv.h"
	#include "omap_fbdev.h"

	MODULE_PARM_DESC(ywrap, "Enable ywrap scrolling (omap44xx and later, default 'y')");
	static bool ywrap_enabled = true;
	module_param_named(ywrap, ywrap_enabled, bool, 0644);

	/*
	* fbdev funcs, to implement legacy fbdev interface on top of drm driver
	*/

	#define to_omap_fbdev(x) container_of(x, struct omap_fbdev, base)

	struct omap_fbdev {
	struct drm_fb_helper base;
	bool ywrap_enabled;

	/* for deferred dmm roll when getting called in atomic ctx */
	struct work_struct work;
	};

	static struct drm_fb_helper get_fb(struct fb_info fbi);

	static void pan_worker(struct work_struct *work)
	{
	struct omap_fbdev *fbdev = container_of(work, struct omap_fbdev, work);
	struct drm_fb_helper *helper = &fbdev->base;
	struct fb_info *fbi = helper->info;
	struct drm_gem_object *bo = drm_gem_fb_get_obj(helper->fb, 0);
	int npages;

	/* DMM roll shifts in 4K pages: */
	npages = fbi->fix.line_length >> PAGE_SHIFT;
	omap_gem_roll(bo, fbi->var.yoffset * npages);
	}

	FB_GEN_DEFAULT_DEFERRED_DMAMEM_OPS(omap_fbdev,
	drm_fb_helper_damage_range,
	drm_fb_helper_damage_area)

	static int omap_fbdev_pan_display(struct fb_var_screeninfo *var,
	struct fb_info *fbi)
	{
	struct drm_fb_helper *helper = get_fb(fbi);
	struct omap_fbdev *fbdev = to_omap_fbdev(helper);

	if (!helper)
	goto fallback;

	if (!fbdev->ywrap_enabled)
	goto fallback;

	if (drm_can_sleep()) {
	pan_worker(&fbdev->work);
	} else {
	struct omap_drm_private *priv = helper->dev->dev_private;
	queue_work(priv->wq, &fbdev->work);
	}

	return 0;

	fallback:
	return drm_fb_helper_pan_display(var, fbi);
	}

	static int omap_fbdev_fb_mmap(struct fb_info info, struct vm_area_struct vma)
	{
	vma->vm_page_prot = pgprot_writecombine(vm_get_page_prot(vma->vm_flags));

	return fb_deferred_io_mmap(info, vma);
	}

	static void omap_fbdev_fb_destroy(struct fb_info *info)
	{
	struct drm_fb_helper *helper = info->par;
	struct drm_framebuffer *fb = helper->fb;
	struct drm_gem_object *bo = drm_gem_fb_get_obj(fb, 0);
	struct omap_fbdev *fbdev = to_omap_fbdev(helper);

	DBG();

	fb_deferred_io_cleanup(info);
	drm_fb_helper_fini(helper);

	omap_gem_unpin(bo);
	drm_framebuffer_remove(fb);

	drm_client_release(&helper->client);
	drm_fb_helper_unprepare(helper);
	kfree(fbdev);
	}

	/*
	* For now, we cannot use FB_DEFAULT_DEFERRED_OPS and fb_deferred_io_mmap()
	* because we use write-combine.
	*/
	static const struct fb_ops omap_fb_ops = {
	.owner = THIS_MODULE,
	__FB_DEFAULT_DEFERRED_OPS_RDWR(omap_fbdev),
	.fb_check_var = drm_fb_helper_check_var,
	.fb_set_par = drm_fb_helper_set_par,
	.fb_setcmap = drm_fb_helper_setcmap,
	.fb_blank = drm_fb_helper_blank,
	.fb_pan_display = omap_fbdev_pan_display,
	__FB_DEFAULT_DEFERRED_OPS_DRAW(omap_fbdev),
	.fb_ioctl = drm_fb_helper_ioctl,
	.fb_mmap = omap_fbdev_fb_mmap,
	.fb_destroy = omap_fbdev_fb_destroy,
	};

	static int omap_fbdev_create(struct drm_fb_helper *helper,
	struct drm_fb_helper_surface_size *sizes)
	{
	struct omap_fbdev *fbdev = to_omap_fbdev(helper);
	struct drm_device *dev = helper->dev;
	struct omap_drm_private *priv = dev->dev_private;
	struct drm_framebuffer *fb = NULL;
	union omap_gem_size gsize;
	struct fb_info *fbi = NULL;
	struct drm_mode_fb_cmd2 mode_cmd = {0};
	struct drm_gem_object *bo;
	dma_addr_t dma_addr;
	int ret;

	sizes->surface_bpp = 32;
	sizes->surface_depth = 24;

	DBG("create fbdev: %dx%d@%d (%dx%d)", sizes->surface_width,
	sizes->surface_height, sizes->surface_bpp,
	sizes->fb_width, sizes->fb_height);

	mode_cmd.pixel_format = drm_mode_legacy_fb_format(sizes->surface_bpp,
	sizes->surface_depth);

	mode_cmd.width = sizes->surface_width;
	mode_cmd.height = sizes->surface_height;

	mode_cmd.pitches[0] =
	DIV_ROUND_UP(mode_cmd.width * sizes->surface_bpp, 8);

	fbdev->ywrap_enabled = priv->has_dmm && ywrap_enabled;
	if (fbdev->ywrap_enabled) {
	/* need to align pitch to page size if using DMM scrolling */
	mode_cmd.pitches[0] = PAGE_ALIGN(mode_cmd.pitches[0]);
	}

	/* allocate backing bo */
	gsize = (union omap_gem_size){
	.bytes = PAGE_ALIGN(mode_cmd.pitches[0] * mode_cmd.height),
	};
	DBG("allocating %d bytes for fb %d", gsize.bytes, dev->primary->index);
	bo = omap_gem_new(dev, gsize, OMAP_BO_SCANOUT \| OMAP_BO_WC);
	if (!bo) {
	dev_err(dev->dev, "failed to allocate buffer object\n");
	ret = -ENOMEM;
	goto fail;
	}

	fb = omap_framebuffer_init(dev, &mode_cmd, &bo);
	if (IS_ERR(fb)) {
	dev_err(dev->dev, "failed to allocate fb\n");
	/* note: if fb creation failed, we can't rely on fb destroy
	* to unref the bo:
	*/
	drm_gem_object_put(bo);
	ret = PTR_ERR(fb);
	goto fail;
	}

	/* note: this keeps the bo pinned.. which is perhaps not ideal,
	* but is needed as long as we use fb_mmap() to mmap to userspace
	* (since this happens using fix.smem_start). Possibly we could
	* implement our own mmap using GEM mmap support to avoid this
	* (non-tiled buffer doesn't need to be pinned for fbcon to write
	* to it). Then we just need to be sure that we are able to re-
	* pin it in case of an opps.
	*/
	ret = omap_gem_pin(bo, &dma_addr);
	if (ret) {
	dev_err(dev->dev, "could not pin framebuffer\n");
	ret = -ENOMEM;
	goto fail;
	}

	fbi = drm_fb_helper_alloc_info(helper);
	if (IS_ERR(fbi)) {
	dev_err(dev->dev, "failed to allocate fb info\n");
	ret = PTR_ERR(fbi);
	goto fail;
	}

	DBG("fbi=%p, dev=%p", fbi, dev);

	helper->fb = fb;

	fbi->fbops = &omap_fb_ops;

	drm_fb_helper_fill_info(fbi, helper, sizes);

	fbi->flags \|= FBINFO_VIRTFB;
	fbi->screen_buffer = omap_gem_vaddr(bo);
	fbi->screen_size = bo->size;
	fbi->fix.smem_start = dma_addr;
	fbi->fix.smem_len = bo->size;

	/* deferred I/O */
	helper->fbdefio.delay = HZ / 20;
	helper->fbdefio.deferred_io = drm_fb_helper_deferred_io;

	fbi->fbdefio = &helper->fbdefio;
	ret = fb_deferred_io_init(fbi);
	if (ret)
	goto fail;

	/* if we have DMM, then we can use it for scrolling by just
	* shuffling pages around in DMM rather than doing sw blit.
	*/
	if (fbdev->ywrap_enabled) {
	DRM_INFO("Enabling DMM ywrap scrolling\n");
	fbi->flags \|= FBINFO_HWACCEL_YWRAP \| FBINFO_READS_FAST;
	fbi->fix.ywrapstep = 1;
	}


	DBG("par=%p, %dx%d", fbi->par, fbi->var.xres, fbi->var.yres);
	DBG("allocated %dx%d fb", fb->width, fb->height);

	return 0;

	fail:

	if (ret) {
	if (fb)
	drm_framebuffer_remove(fb);
	}

	return ret;
	}

	static int omap_fbdev_dirty(struct drm_fb_helper helper, struct drm_clip_rect clip)
	{
	if (!(clip->x1 < clip->x2 && clip->y1 < clip->y2))
	return 0;

	if (helper->fb->funcs->dirty)
	return helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, clip, 1);

	return 0;
	}

	static const struct drm_fb_helper_funcs omap_fb_helper_funcs = {
	.fb_probe = omap_fbdev_create,
	.fb_dirty = omap_fbdev_dirty,
	};

	static struct drm_fb_helper get_fb(struct fb_info fbi)
	{
	if (!fbi \|\| strcmp(fbi->fix.id, MODULE_NAME)) {
	/* these are not the fb's you're looking for */
	return NULL;
	}
	return fbi->par;
	}

	/*
	* struct drm_client
	*/

	static void omap_fbdev_client_unregister(struct drm_client_dev *client)
	{
	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);

	if (fb_helper->info) {
	drm_fb_helper_unregister_info(fb_helper);
	} else {
	drm_client_release(&fb_helper->client);
	drm_fb_helper_unprepare(fb_helper);
	kfree(fb_helper);
	}
	}

	static int omap_fbdev_client_restore(struct drm_client_dev *client)
	{
	drm_fb_helper_lastclose(client->dev);

	return 0;
	}

	static int omap_fbdev_client_hotplug(struct drm_client_dev *client)
	{
	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
	struct drm_device *dev = client->dev;
	int ret;

	if (dev->fb_helper)
	return drm_fb_helper_hotplug_event(dev->fb_helper);

	ret = drm_fb_helper_init(dev, fb_helper);
	if (ret)
	goto err_drm_err;

	ret = drm_fb_helper_initial_config(fb_helper);
	if (ret)
	goto err_drm_fb_helper_fini;

	return 0;

	err_drm_fb_helper_fini:
	drm_fb_helper_fini(fb_helper);
	err_drm_err:
	drm_err(dev, "Failed to setup fbdev emulation (ret=%d)\n", ret);
	return ret;
	}

	static const struct drm_client_funcs omap_fbdev_client_funcs = {
	.owner = THIS_MODULE,
	.unregister = omap_fbdev_client_unregister,
	.restore = omap_fbdev_client_restore,
	.hotplug = omap_fbdev_client_hotplug,
	};

	void omap_fbdev_setup(struct drm_device *dev)
	{
	struct omap_fbdev *fbdev;
	struct drm_fb_helper *helper;
	int ret;

	drm_WARN(dev, !dev->registered, "Device has not been registered.\n");
	drm_WARN(dev, dev->fb_helper, "fb_helper is already set!\n");

	fbdev = kzalloc(sizeof(*fbdev), GFP_KERNEL);
	if (!fbdev)
	return;
	helper = &fbdev->base;

	drm_fb_helper_prepare(dev, helper, 32, &omap_fb_helper_funcs);

	ret = drm_client_init(dev, &helper->client, "fbdev", &omap_fbdev_client_funcs);
	if (ret)
	goto err_drm_client_init;

	INIT_WORK(&fbdev->work, pan_worker);

	drm_client_register(&helper->client);

	return;

	err_drm_client_init:
	drm_fb_helper_unprepare(helper);
	kfree(fbdev);
	}