[v4,1/5] drm/ofdrm: Add ofdrm for Open Firmware framebuffers

diff --git a/MAINTAINERS b/MAINTAINERS
index 7c7db809473e..dcb443f2496b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6656,6 +6656,7 @@  L:	dri-devel@lists.freedesktop.org
 S:	Maintained
 T:	git git://anongit.freedesktop.org/drm/drm-misc
 F:	drivers/gpu/drm/drm_aperture.c
+F:	drivers/gpu/drm/tiny/ofdrm.c
 F:	drivers/gpu/drm/tiny/simpledrm.c
 F:	drivers/video/aperture.c
 F:	include/drm/drm_aperture.h
diff --git a/drivers/gpu/drm/tiny/Kconfig b/drivers/gpu/drm/tiny/Kconfig
index 565957264875..a300b03a3c7a 100644
--- a/drivers/gpu/drm/tiny/Kconfig
+++ b/drivers/gpu/drm/tiny/Kconfig
@@ -51,6 +51,19 @@  config DRM_GM12U320
 	 This is a KMS driver for projectors which use the GM12U320 chipset
 	 for video transfer over USB2/3, such as the Acer C120 mini projector.
 
+config DRM_OFDRM
+	tristate "Open Firmware display driver"
+	depends on DRM && OF && (PPC || COMPILE_TEST)
+	select APERTURE_HELPERS
+	select DRM_GEM_SHMEM_HELPER
+	select DRM_KMS_HELPER
+	help
+	  DRM driver for Open Firmware framebuffers.
+
+	  This driver assumes that the display hardware has been initialized
+	  by the Open Firmware before the kernel boots. Scanout buffer, size,
+	  and display format must be provided via device tree.
+
 config DRM_PANEL_MIPI_DBI
 	tristate "DRM support for MIPI DBI compatible panels"
 	depends on DRM && SPI
diff --git a/drivers/gpu/drm/tiny/Makefile b/drivers/gpu/drm/tiny/Makefile
index 1d9d6227e7ab..76dde89a044b 100644
--- a/drivers/gpu/drm/tiny/Makefile
+++ b/drivers/gpu/drm/tiny/Makefile
@@ -4,6 +4,7 @@  obj-$(CONFIG_DRM_ARCPGU)		+= arcpgu.o
 obj-$(CONFIG_DRM_BOCHS)			+= bochs.o
 obj-$(CONFIG_DRM_CIRRUS_QEMU)		+= cirrus.o
 obj-$(CONFIG_DRM_GM12U320)		+= gm12u320.o
+obj-$(CONFIG_DRM_OFDRM)			+= ofdrm.o
 obj-$(CONFIG_DRM_PANEL_MIPI_DBI)	+= panel-mipi-dbi.o
 obj-$(CONFIG_DRM_SIMPLEDRM)		+= simpledrm.o
 obj-$(CONFIG_TINYDRM_HX8357D)		+= hx8357d.o
diff --git a/drivers/gpu/drm/tiny/ofdrm.c b/drivers/gpu/drm/tiny/ofdrm.c
new file mode 100644
index 000000000000..98bd99ab7e46
--- /dev/null
+++ b/drivers/gpu/drm/tiny/ofdrm.c
@@ -0,0 +1,760 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/of_address.h>
+#include <linux/pci.h>
+#include <linux/platform_device.h>
+
+#include <drm/drm_aperture.h>
+#include <drm/drm_atomic.h>
+#include <drm/drm_atomic_state_helper.h>
+#include <drm/drm_connector.h>
+#include <drm/drm_damage_helper.h>
+#include <drm/drm_device.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fb_helper.h>
+#include <drm/drm_format_helper.h>
+#include <drm/drm_gem_atomic_helper.h>
+#include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_gem_shmem_helper.h>
+#include <drm/drm_managed.h>
+#include <drm/drm_modeset_helper_vtables.h>
+#include <drm/drm_plane_helper.h>
+#include <drm/drm_probe_helper.h>
+#include <drm/drm_simple_kms_helper.h>
+
+#define DRIVER_NAME	"ofdrm"
+#define DRIVER_DESC	"DRM driver for OF platform devices"
+#define DRIVER_DATE	"20220501"
+#define DRIVER_MAJOR	1
+#define DRIVER_MINOR	0
+
+/*
+ * Helpers for display nodes
+ */
+
+static int display_get_validated_int(struct drm_device *dev, const char *name, uint32_t value)
+{
+	if (value > INT_MAX) {
+		drm_err(dev, "invalid framebuffer %s of %u\n", name, value);
+		return -EINVAL;
+	}
+	return (int)value;
+}
+
+static int display_get_validated_int0(struct drm_device *dev, const char *name, uint32_t value)
+{
+	if (!value) {
+		drm_err(dev, "invalid framebuffer %s of %u\n", name, value);
+		return -EINVAL;
+	}
+	return display_get_validated_int(dev, name, value);
+}
+
+static const struct drm_format_info *display_get_validated_format(struct drm_device *dev,
+								  u32 depth)
+{
+	const struct drm_format_info *info;
+	u32 format;
+
+	switch (depth) {
+	case 8:
+		format = drm_mode_legacy_fb_format(8, 8);
+		break;
+	case 15:
+	case 16:
+		format = drm_mode_legacy_fb_format(16, depth);
+		break;
+	case 32:
+		format = drm_mode_legacy_fb_format(32, 24);
+		break;
+	default:
+		drm_err(dev, "unsupported framebuffer depth %u\n", depth);
+		return ERR_PTR(-EINVAL);
+	}
+
+	info = drm_format_info(format);
+	if (!info) {
+		drm_err(dev, "cannot find framebuffer format for depth %u\n", depth);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return info;
+}
+
+static int display_read_u32_of(struct drm_device *dev, struct device_node *of_node,
+			       const char *name, u32 *value)
+{
+	int ret = of_property_read_u32(of_node, name, value);
+
+	if (ret)
+		drm_err(dev, "cannot parse framebuffer %s: error %d\n", name, ret);
+	return ret;
+}
+
+static int display_get_width_of(struct drm_device *dev, struct device_node *of_node)
+{
+	u32 width;
+	int ret = display_read_u32_of(dev, of_node, "width", &width);
+
+	if (ret)
+		return ret;
+	return display_get_validated_int0(dev, "width", width);
+}
+
+static int display_get_height_of(struct drm_device *dev, struct device_node *of_node)
+{
+	u32 height;
+	int ret = display_read_u32_of(dev, of_node, "height", &height);
+
+	if (ret)
+		return ret;
+	return display_get_validated_int0(dev, "height", height);
+}
+
+static int display_get_depth_of(struct drm_device *dev, struct device_node *of_node)
+{
+	u32 depth;
+	int ret = display_read_u32_of(dev, of_node, "depth", &depth);
+
+	if (ret)
+		return ret;
+	return display_get_validated_int0(dev, "depth", depth);
+}
+
+static int display_get_linebytes_of(struct drm_device *dev, struct device_node *of_node)
+{
+	u32 linebytes;
+	int ret = display_read_u32_of(dev, of_node, "linebytes", &linebytes);
+
+	if (ret)
+		return ret;
+	return display_get_validated_int(dev, "linebytes", linebytes);
+}
+
+static u64 display_get_address_of(struct drm_device *dev, struct device_node *of_node)
+{
+	u32 address;
+	int ret;
+
+	/*
+	 * Not all devices provide an address property, it's not
+	 * a bug if this fails. The driver will try to find the
+	 * framebuffer base address from the device's memory regions.
+	 */
+	ret = of_property_read_u32(of_node, "address", &address);
+	if (ret)
+		return OF_BAD_ADDR;
+
+	return address;
+}
+
+/*
+ * Open Firmware display device
+ */
+
+struct ofdrm_device {
+	struct drm_device dev;
+	struct platform_device *pdev;
+
+	/* firmware-buffer settings */
+	struct iosys_map screen_base;
+	struct drm_display_mode mode;
+	const struct drm_format_info *format;
+	unsigned int pitch;
+
+	/* modesetting */
+	uint32_t formats[8];
+	struct drm_plane primary_plane;
+	struct drm_crtc crtc;
+	struct drm_encoder encoder;
+	struct drm_connector connector;
+};
+
+static struct ofdrm_device *ofdrm_device_of_dev(struct drm_device *dev)
+{
+	return container_of(dev, struct ofdrm_device, dev);
+}
+
+/*
+ * Hardware
+ */
+
+#if defined(CONFIG_PCI)
+static struct pci_dev *display_get_pci_dev_of(struct drm_device *dev, struct device_node *of_node)
+{
+	const __be32 *vendor_p, *device_p;
+	u32 vendor, device;
+	struct pci_dev *pcidev;
+
+	vendor_p = of_get_property(of_node, "vendor-id", NULL);
+	if (!vendor_p)
+		return ERR_PTR(-ENODEV);
+	vendor = be32_to_cpup(vendor_p);
+
+	device_p = of_get_property(of_node, "device-id", NULL);
+	if (!device_p)
+		return ERR_PTR(-ENODEV);
+	device = be32_to_cpup(device_p);
+
+	pcidev = pci_get_device(vendor, device, NULL);
+	if (!pcidev)
+		return ERR_PTR(-ENODEV);
+
+	return pcidev;
+}
+
+static void ofdrm_pci_release(void *data)
+{
+	struct pci_dev *pcidev = data;
+
+	pci_disable_device(pcidev);
+}
+
+static int ofdrm_device_init_pci(struct ofdrm_device *odev)
+{
+	struct drm_device *dev = &odev->dev;
+	struct platform_device *pdev = to_platform_device(dev->dev);
+	struct device_node *of_node = pdev->dev.of_node;
+	struct pci_dev *pcidev;
+	int ret;
+
+	/*
+	 * Never use pcim_ or other managed helpers on the returned PCI
+	 * device. Otherwise, probing the native driver will fail for
+	 * resource conflicts. PCI-device management has to be tied to
+	 * the lifetime of the platform device until the native driver
+	 * takes over.
+	 */
+	pcidev = display_get_pci_dev_of(dev, of_node);
+	if (IS_ERR(pcidev))
+		return 0; /* no PCI device found; ignore the error */
+
+	ret = pci_enable_device(pcidev);
+	if (ret) {
+		drm_err(dev, "pci_enable_device(%s) failed: %d\n",
+			dev_name(&pcidev->dev), ret);
+		return ret;
+	}
+	ret = devm_add_action_or_reset(&pdev->dev, ofdrm_pci_release, pcidev);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+#else
+static int ofdrm_device_init_pci(struct ofdrm_device *odev)
+{
+	return 0;
+}
+#endif
+
+/*
+ *  OF display settings
+ */
+
+static struct resource *ofdrm_find_fb_resource(struct ofdrm_device *odev,
+					       struct resource *fb_res)
+{
+	struct platform_device *pdev = to_platform_device(odev->dev.dev);
+	struct resource *res, *max_res = NULL;
+	u32 i;
+
+	for (i = 0; pdev->num_resources; ++i) {
+		res = platform_get_resource(pdev, IORESOURCE_MEM, i);
+		if (!res)
+			break; /* all resources processed */
+		if (resource_size(res) < resource_size(fb_res))
+			continue; /* resource too small */
+		if (fb_res->start && resource_contains(res, fb_res))
+			return res; /* resource contains framebuffer */
+		if (!max_res || resource_size(res) > resource_size(max_res))
+			max_res = res; /* store largest resource as fallback */
+	}
+
+	return max_res;
+}
+
+/*
+ * Modesetting
+ */
+
+/*
+ * Support all formats of OF display and maybe more; in order
+ * of preference. The display's update function will do any
+ * conversion necessary.
+ *
+ * TODO: Add blit helpers for remaining formats and uncomment
+ *       constants.
+ */
+static const uint32_t ofdrm_primary_plane_formats[] = {
+	DRM_FORMAT_XRGB8888,
+	DRM_FORMAT_RGB565,
+	//DRM_FORMAT_XRGB1555,
+	//DRM_FORMAT_C8,
+};
+
+static const uint64_t ofdrm_primary_plane_format_modifiers[] = {
+	DRM_FORMAT_MOD_LINEAR,
+	DRM_FORMAT_MOD_INVALID
+};
+
+static int ofdrm_primary_plane_helper_atomic_check(struct drm_plane *plane,
+						   struct drm_atomic_state *new_state)
+{
+	struct drm_plane_state *new_plane_state = drm_atomic_get_new_plane_state(new_state, plane);
+	struct drm_crtc *new_crtc = new_plane_state->crtc;
+	struct drm_crtc_state *new_crtc_state = NULL;
+
+	if (new_crtc)
+		new_crtc_state = drm_atomic_get_new_crtc_state(new_state, new_plane_state->crtc);
+
+	return drm_atomic_helper_check_plane_state(new_plane_state, new_crtc_state,
+						   DRM_PLANE_NO_SCALING,
+						   DRM_PLANE_NO_SCALING,
+						   false, false);
+}
+
+static void ofdrm_primary_plane_helper_atomic_update(struct drm_plane *plane,
+						     struct drm_atomic_state *state)
+{
+	struct drm_device *dev = plane->dev;
+	struct ofdrm_device *odev = ofdrm_device_of_dev(dev);
+	struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane);
+	struct drm_plane_state *old_plane_state = drm_atomic_get_old_plane_state(state, plane);
+	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
+	struct drm_framebuffer *fb = plane_state->fb;
+	unsigned int dst_pitch = odev->pitch;
+	const struct drm_format_info *dst_format = odev->format;
+	struct drm_atomic_helper_damage_iter iter;
+	struct drm_rect damage;
+	int ret, idx;
+
+	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
+	if (ret)
+		return;
+
+	if (!drm_dev_enter(dev, &idx))
+		goto out_drm_gem_fb_end_cpu_access;
+
+	drm_atomic_helper_damage_iter_init(&iter, old_plane_state, plane_state);
+	drm_atomic_for_each_plane_damage(&iter, &damage) {
+		struct iosys_map dst = odev->screen_base;
+		struct drm_rect dst_clip = plane_state->dst;
+
+		if (!drm_rect_intersect(&dst_clip, &damage))
+			continue;
+
+		iosys_map_incr(&dst, drm_fb_clip_offset(dst_pitch, dst_format, &dst_clip));
+		drm_fb_blit(&dst, &dst_pitch, dst_format->format, shadow_plane_state->data, fb,
+			    &damage);
+	}
+
+	drm_dev_exit(idx);
+out_drm_gem_fb_end_cpu_access:
+	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
+}
+
+static void ofdrm_primary_plane_helper_atomic_disable(struct drm_plane *plane,
+						      struct drm_atomic_state *state)
+{
+	struct drm_device *dev = plane->dev;
+	struct ofdrm_device *odev = ofdrm_device_of_dev(dev);
+	struct iosys_map dst = odev->screen_base;
+	struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane);
+	void __iomem *dst_vmap = dst.vaddr_iomem; /* TODO: Use mapping abstraction */
+	unsigned int dst_pitch = odev->pitch;
+	const struct drm_format_info *dst_format = odev->format;
+	struct drm_rect dst_clip;
+	unsigned long lines, linepixels, i;
+	int idx;
+
+	drm_rect_init(&dst_clip,
+		      plane_state->src_x >> 16, plane_state->src_y >> 16,
+		      plane_state->src_w >> 16, plane_state->src_h >> 16);
+
+	lines = drm_rect_height(&dst_clip);
+	linepixels = drm_rect_width(&dst_clip);
+
+	if (!drm_dev_enter(dev, &idx))
+		return;
+
+	/* Clear buffer to black if disabled */
+	dst_vmap += drm_fb_clip_offset(dst_pitch, dst_format, &dst_clip);
+	for (i = 0; i < lines; ++i) {
+		memset_io(dst_vmap, 0, linepixels * dst_format->cpp[0]);
+		dst_vmap += dst_pitch;
+	}
+
+	drm_dev_exit(idx);
+}
+
+static const struct drm_plane_helper_funcs ofdrm_primary_plane_helper_funcs = {
+	DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
+	.atomic_check = ofdrm_primary_plane_helper_atomic_check,
+	.atomic_update = ofdrm_primary_plane_helper_atomic_update,
+	.atomic_disable = ofdrm_primary_plane_helper_atomic_disable,
+};
+
+static const struct drm_plane_funcs ofdrm_primary_plane_funcs = {
+	.update_plane = drm_atomic_helper_update_plane,
+	.disable_plane = drm_atomic_helper_disable_plane,
+	.destroy = drm_plane_cleanup,
+	DRM_GEM_SHADOW_PLANE_FUNCS,
+};
+
+static enum drm_mode_status ofdrm_crtc_helper_mode_valid(struct drm_crtc *crtc,
+							 const struct drm_display_mode *mode)
+{
+	struct ofdrm_device *odev = ofdrm_device_of_dev(crtc->dev);
+
+	return drm_crtc_helper_mode_valid_fixed(crtc, mode, &odev->mode);
+}
+
+static int ofdrm_crtc_helper_atomic_check(struct drm_crtc *crtc,
+					  struct drm_atomic_state *new_state)
+{
+	struct drm_crtc_state *new_crtc_state = drm_atomic_get_new_crtc_state(new_state, crtc);
+
+	return drm_atomic_helper_check_crtc_state(new_crtc_state, false);
+}
+
+/*
+ * The CRTC is always enabled. Screen updates are performed by
+ * the primary plane's atomic_update function. Disabling clears
+ * the screen in the primary plane's atomic_disable function.
+ */
+static const struct drm_crtc_helper_funcs ofdrm_crtc_helper_funcs = {
+	.mode_valid = ofdrm_crtc_helper_mode_valid,
+	.atomic_check = ofdrm_crtc_helper_atomic_check,
+};
+
+static const struct drm_crtc_funcs ofdrm_crtc_funcs = {
+	.reset = drm_atomic_helper_crtc_reset,
+	.destroy = drm_crtc_cleanup,
+	.set_config = drm_atomic_helper_set_config,
+	.page_flip = drm_atomic_helper_page_flip,
+	.atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
+};
+
+static int ofdrm_connector_helper_get_modes(struct drm_connector *connector)
+{
+	struct ofdrm_device *odev = ofdrm_device_of_dev(connector->dev);
+
+	return drm_connector_helper_get_modes_fixed(connector, &odev->mode);
+}
+
+static const struct drm_connector_helper_funcs ofdrm_connector_helper_funcs = {
+	.get_modes = ofdrm_connector_helper_get_modes,
+};
+
+static const struct drm_connector_funcs ofdrm_connector_funcs = {
+	.reset = drm_atomic_helper_connector_reset,
+	.fill_modes = drm_helper_probe_single_connector_modes,
+	.destroy = drm_connector_cleanup,
+	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+static const struct drm_mode_config_funcs ofdrm_mode_config_funcs = {
+	.fb_create = drm_gem_fb_create_with_dirty,
+	.atomic_check = drm_atomic_helper_check,
+	.atomic_commit = drm_atomic_helper_commit,
+};
+
+/*
+ * Init / Cleanup
+ */
+
+static struct drm_display_mode ofdrm_mode(unsigned int width, unsigned int height)
+{
+	/*
+	 * Assume a monitor resolution of 96 dpi to
+	 * get a somewhat reasonable screen size.
+	 */
+	const struct drm_display_mode mode = {
+		DRM_MODE_INIT(60, width, height,
+			      DRM_MODE_RES_MM(width, 96ul),
+			      DRM_MODE_RES_MM(height, 96ul))
+	};
+
+	return mode;
+}
+
+static struct ofdrm_device *ofdrm_device_create(struct drm_driver *drv,
+						struct platform_device *pdev)
+{
+	struct device_node *of_node = pdev->dev.of_node;
+	struct ofdrm_device *odev;
+	struct drm_device *dev;
+	int width, height, depth, linebytes;
+	const struct drm_format_info *format;
+	u64 address;
+	resource_size_t fb_size, fb_base, fb_pgbase, fb_pgsize;
+	struct resource *res, *mem;
+	void __iomem *screen_base;
+	struct drm_plane *primary_plane;
+	struct drm_crtc *crtc;
+	struct drm_encoder *encoder;
+	struct drm_connector *connector;
+	unsigned long max_width, max_height;
+	size_t nformats;
+	int ret;
+
+	odev = devm_drm_dev_alloc(&pdev->dev, drv, struct ofdrm_device, dev);
+	if (IS_ERR(odev))
+		return ERR_CAST(odev);
+	dev = &odev->dev;
+	platform_set_drvdata(pdev, dev);
+
+	ret = ofdrm_device_init_pci(odev);
+	if (ret)
+		return ERR_PTR(ret);
+
+	/*
+	 * OF display-node settings
+	 */
+
+	width = display_get_width_of(dev, of_node);
+	if (width < 0)
+		return ERR_PTR(width);
+	height = display_get_height_of(dev, of_node);
+	if (height < 0)
+		return ERR_PTR(height);
+	depth = display_get_depth_of(dev, of_node);
+	if (depth < 0)
+		return ERR_PTR(depth);
+	linebytes = display_get_linebytes_of(dev, of_node);
+	if (linebytes < 0)
+		return ERR_PTR(linebytes);
+
+	format = display_get_validated_format(dev, depth);
+	if (IS_ERR(format))
+		return ERR_CAST(format);
+	if (!linebytes) {
+		linebytes = drm_format_info_min_pitch(format, 0, width);
+		if (drm_WARN_ON(dev, !linebytes))
+			return ERR_PTR(-EINVAL);
+	}
+
+	fb_size = linebytes * height;
+
+	/*
+	 * Try to figure out the address of the framebuffer. Unfortunately, Open
+	 * Firmware doesn't provide a standard way to do so. All we can do is a
+	 * dodgy heuristic that happens to work in practice.
+	 *
+	 * On most machines, the "address" property contains what we need, though
+	 * not on Matrox cards found in IBM machines. What appears to give good
+	 * results is to go through the PCI ranges and pick one that encloses the
+	 * "address" property. If none match, we pick the largest.
+	 */
+	address = display_get_address_of(dev, of_node);
+	if (address != OF_BAD_ADDR) {
+		struct resource fb_res = DEFINE_RES_MEM(address, fb_size);
+
+		res = ofdrm_find_fb_resource(odev, &fb_res);
+		if (!res)
+			return ERR_PTR(-EINVAL);
+		if (resource_contains(res, &fb_res))
+			fb_base = address;
+		else
+			fb_base = res->start;
+	} else {
+		struct resource fb_res = DEFINE_RES_MEM(0u, fb_size);
+
+		res = ofdrm_find_fb_resource(odev, &fb_res);
+		if (!res)
+			return ERR_PTR(-EINVAL);
+		fb_base = res->start;
+	}
+
+	/*
+	 * I/O resources
+	 */
+
+	fb_pgbase = round_down(fb_base, PAGE_SIZE);
+	fb_pgsize = fb_base - fb_pgbase + round_up(fb_size, PAGE_SIZE);
+
+	ret = devm_aperture_acquire_from_firmware(dev, fb_pgbase, fb_pgsize);
+	if (ret) {
+		drm_err(dev, "could not acquire memory range %pr: error %d\n", &res, ret);
+		return ERR_PTR(ret);
+	}
+
+	mem = devm_request_mem_region(&pdev->dev, fb_pgbase, fb_pgsize, drv->name);
+	if (!mem) {
+		drm_warn(dev, "could not acquire memory region %pr\n", &res);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	screen_base = devm_ioremap(&pdev->dev, mem->start, resource_size(mem));
+	if (!screen_base)
+		return ERR_PTR(-ENOMEM);
+
+	/*
+	 * Firmware framebuffer
+	 */
+
+	iosys_map_set_vaddr_iomem(&odev->screen_base, screen_base);
+	odev->mode = ofdrm_mode(width, height);
+	odev->format = format;
+	odev->pitch = linebytes;
+
+	drm_dbg(dev, "display mode={" DRM_MODE_FMT "}\n", DRM_MODE_ARG(&odev->mode));
+	drm_dbg(dev, "framebuffer format=%p4cc, size=%dx%d, linebytes=%d byte\n",
+		&format->format, width, height, linebytes);
+
+	/*
+	 * Mode-setting pipeline
+	 */
+
+	ret = drmm_mode_config_init(dev);
+	if (ret)
+		return ERR_PTR(ret);
+
+	max_width = max_t(unsigned long, width, DRM_SHADOW_PLANE_MAX_WIDTH);
+	max_height = max_t(unsigned long, height, DRM_SHADOW_PLANE_MAX_HEIGHT);
+
+	dev->mode_config.min_width = width;
+	dev->mode_config.max_width = max_width;
+	dev->mode_config.min_height = height;
+	dev->mode_config.max_height = max_height;
+	dev->mode_config.funcs = &ofdrm_mode_config_funcs;
+	switch (depth) {
+	case 32:
+		dev->mode_config.preferred_depth = 24;
+		break;
+	default:
+		dev->mode_config.preferred_depth = depth;
+		break;
+	}
+
+	/* Primary plane */
+
+	nformats = drm_fb_build_fourcc_list(dev, &format->format, 1,
+					    ofdrm_primary_plane_formats,
+					    ARRAY_SIZE(ofdrm_primary_plane_formats),
+					    odev->formats, ARRAY_SIZE(odev->formats));
+
+	primary_plane = &odev->primary_plane;
+	ret = drm_universal_plane_init(dev, primary_plane, 0, &ofdrm_primary_plane_funcs,
+				       odev->formats, nformats,
+				       ofdrm_primary_plane_format_modifiers,
+				       DRM_PLANE_TYPE_PRIMARY, NULL);
+	if (ret)
+		return ERR_PTR(ret);
+	drm_plane_helper_add(primary_plane, &ofdrm_primary_plane_helper_funcs);
+	drm_plane_enable_fb_damage_clips(primary_plane);
+
+	/* CRTC */
+
+	crtc = &odev->crtc;
+	ret = drm_crtc_init_with_planes(dev, crtc, primary_plane, NULL,
+					&ofdrm_crtc_funcs, NULL);
+	if (ret)
+		return ERR_PTR(ret);
+	drm_crtc_helper_add(crtc, &ofdrm_crtc_helper_funcs);
+
+	/* Encoder */
+
+	encoder = &odev->encoder;
+	ret = drm_simple_encoder_init(dev, encoder, DRM_MODE_ENCODER_NONE);
+	if (ret)
+		return ERR_PTR(ret);
+	encoder->possible_crtcs = drm_crtc_mask(crtc);
+
+	/* Connector */
+
+	connector = &odev->connector;
+	ret = drm_connector_init(dev, connector, &ofdrm_connector_funcs,
+				 DRM_MODE_CONNECTOR_Unknown);
+	if (ret)
+		return ERR_PTR(ret);
+	drm_connector_helper_add(connector, &ofdrm_connector_helper_funcs);
+	drm_connector_set_panel_orientation_with_quirk(connector,
+						       DRM_MODE_PANEL_ORIENTATION_UNKNOWN,
+						       width, height);
+
+	ret = drm_connector_attach_encoder(connector, encoder);
+	if (ret)
+		return ERR_PTR(ret);
+
+	drm_mode_config_reset(dev);
+
+	return odev;
+}
+
+/*
+ * DRM driver
+ */
+
+DEFINE_DRM_GEM_FOPS(ofdrm_fops);
+
+static struct drm_driver ofdrm_driver = {
+	DRM_GEM_SHMEM_DRIVER_OPS,
+	.name			= DRIVER_NAME,
+	.desc			= DRIVER_DESC,
+	.date			= DRIVER_DATE,
+	.major			= DRIVER_MAJOR,
+	.minor			= DRIVER_MINOR,
+	.driver_features	= DRIVER_ATOMIC | DRIVER_GEM | DRIVER_MODESET,
+	.fops			= &ofdrm_fops,
+};
+
+/*
+ * Platform driver
+ */
+
+static int ofdrm_probe(struct platform_device *pdev)
+{
+	struct ofdrm_device *odev;
+	struct drm_device *dev;
+	int ret;
+
+	odev = ofdrm_device_create(&ofdrm_driver, pdev);
+	if (IS_ERR(odev))
+		return PTR_ERR(odev);
+	dev = &odev->dev;
+
+	ret = drm_dev_register(dev, 0);
+	if (ret)
+		return ret;
+
+	/*
+	 * FIXME: 24-bit color depth does not work reliably with a 32-bpp
+	 * value. Force the bpp value of the scanout buffer's format.
+	 */
+	drm_fbdev_generic_setup(dev, drm_format_info_bpp(odev->format, 0));
+
+	return 0;
+}
+
+static int ofdrm_remove(struct platform_device *pdev)
+{
+	struct drm_device *dev = platform_get_drvdata(pdev);
+
+	drm_dev_unplug(dev);
+
+	return 0;
+}
+
+static const struct of_device_id ofdrm_of_match_display[] = {
+	{ .compatible = "display", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ofdrm_of_match_display);
+
+static struct platform_driver ofdrm_platform_driver = {
+	.driver = {
+		.name = "of-display",
+		.of_match_table = ofdrm_of_match_display,
+	},
+	.probe = ofdrm_probe,
+	.remove = ofdrm_remove,
+};
+
+module_platform_driver(ofdrm_platform_driver);
+
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index cfc55273dc5d..a98987aa2784 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig
@@ -455,6 +455,7 @@  config FB_ATARI
 config FB_OF
 	bool "Open Firmware frame buffer device support"
 	depends on (FB = y) && PPC && (!PPC_PSERIES || PCI)
+	depends on !DRM_OFDRM
 	select APERTURE_HELPERS
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA