drivers/gpu/drm/udl/udl_modeset.c - linux/torvalds/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2012 Red Hat
  *
  * based in parts on udlfb.c:
  * Copyright (C) 2009 Roberto De Ioris <roberto@unbit.it>
  * Copyright (C) 2009 Jaya Kumar <jayakumar.lkml@gmail.com>
  * Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>

  */

 #include <linux/dma-buf.h>

 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_gem_framebuffer_helper.h>
 #include <drm/drm_gem_shmem_helper.h>
 #include <drm/drm_modeset_helper_vtables.h>
 #include <drm/drm_vblank.h>

 #include "udl_drv.h"

 #define UDL_COLOR_DEPTH_16BPP	0

 /*
  * All DisplayLink bulk operations start with 0xAF, followed by specific code
  * All operations are written to buffers which then later get sent to device
  */
 static char *udl_set_register(char *buf, u8 reg, u8 val)
 {
 	*buf++ = 0xAF;
 	*buf++ = 0x20;
 	*buf++ = reg;
 	*buf++ = val;
 	return buf;
 }

 static char *udl_vidreg_lock(char *buf)
 {
 	return udl_set_register(buf, 0xFF, 0x00);
 }

 static char *udl_vidreg_unlock(char *buf)
 {
 	return udl_set_register(buf, 0xFF, 0xFF);
 }

 static char *udl_set_blank_mode(char *buf, u8 mode)
 {
 	return udl_set_register(buf, UDL_REG_BLANK_MODE, mode);
 }

 static char *udl_set_color_depth(char *buf, u8 selection)
 {
 	return udl_set_register(buf, 0x00, selection);
 }

 static char *udl_set_base16bpp(char *wrptr, u32 base)
 {
 	/* the base pointer is 16 bits wide, 0x20 is hi byte. */
 	wrptr = udl_set_register(wrptr, 0x20, base >> 16);
 	wrptr = udl_set_register(wrptr, 0x21, base >> 8);
 	return udl_set_register(wrptr, 0x22, base);
 }

 /*
  * DisplayLink HW has separate 16bpp and 8bpp framebuffers.
  * In 24bpp modes, the low 323 RGB bits go in the 8bpp framebuffer
  */
 static char *udl_set_base8bpp(char *wrptr, u32 base)
 {
 	wrptr = udl_set_register(wrptr, 0x26, base >> 16);
 	wrptr = udl_set_register(wrptr, 0x27, base >> 8);
 	return udl_set_register(wrptr, 0x28, base);
 }

 static char *udl_set_register_16(char *wrptr, u8 reg, u16 value)
 {
 	wrptr = udl_set_register(wrptr, reg, value >> 8);
 	return udl_set_register(wrptr, reg+1, value);
 }

 /*
  * This is kind of weird because the controller takes some
  * register values in a different byte order than other registers.
  */
 static char *udl_set_register_16be(char *wrptr, u8 reg, u16 value)
 {
 	wrptr = udl_set_register(wrptr, reg, value);
 	return udl_set_register(wrptr, reg+1, value >> 8);
 }

 /*
  * LFSR is linear feedback shift register. The reason we have this is
  * because the display controller needs to minimize the clock depth of
  * various counters used in the display path. So this code reverses the
  * provided value into the lfsr16 value by counting backwards to get
  * the value that needs to be set in the hardware comparator to get the
  * same actual count. This makes sense once you read above a couple of
  * times and think about it from a hardware perspective.
  */
 static u16 udl_lfsr16(u16 actual_count)
 {
 	u32 lv = 0xFFFF; /* This is the lfsr value that the hw starts with */

 	while (actual_count--) {
 		lv =	 ((lv << 1) |
 			(((lv >> 15) ^ (lv >> 4) ^ (lv >> 2) ^ (lv >> 1)) & 1))
 			& 0xFFFF;
 	}

 	return (u16) lv;
 }

 /*
  * This does LFSR conversion on the value that is to be written.
  * See LFSR explanation above for more detail.
  */
 static char *udl_set_register_lfsr16(char *wrptr, u8 reg, u16 value)
 {
 	return udl_set_register_16(wrptr, reg, udl_lfsr16(value));
 }

 /*
  * This takes a standard fbdev screeninfo struct and all of its monitor mode
  * details and converts them into the DisplayLink equivalent register commands.
   ERR(vreg(dev,               0x00, (color_depth == 16) ? 0 : 1));
   ERR(vreg_lfsr16(dev,        0x01, xDisplayStart));
   ERR(vreg_lfsr16(dev,        0x03, xDisplayEnd));
   ERR(vreg_lfsr16(dev,        0x05, yDisplayStart));
   ERR(vreg_lfsr16(dev,        0x07, yDisplayEnd));
   ERR(vreg_lfsr16(dev,        0x09, xEndCount));
   ERR(vreg_lfsr16(dev,        0x0B, hSyncStart));
   ERR(vreg_lfsr16(dev,        0x0D, hSyncEnd));
   ERR(vreg_big_endian(dev,    0x0F, hPixels));
   ERR(vreg_lfsr16(dev,        0x11, yEndCount));
   ERR(vreg_lfsr16(dev,        0x13, vSyncStart));
   ERR(vreg_lfsr16(dev,        0x15, vSyncEnd));
   ERR(vreg_big_endian(dev,    0x17, vPixels));
   ERR(vreg_little_endian(dev, 0x1B, pixelClock5KHz));

   ERR(vreg(dev,               0x1F, 0));

   ERR(vbuf(dev, WRITE_VIDREG_UNLOCK, DSIZEOF(WRITE_VIDREG_UNLOCK)));
  */
 static char *udl_set_vid_cmds(char *wrptr, struct drm_display_mode *mode)
 {
 	u16 xds, yds;
 	u16 xde, yde;
 	u16 yec;

 	/* x display start */
 	xds = mode->crtc_htotal - mode->crtc_hsync_start;
 	wrptr = udl_set_register_lfsr16(wrptr, 0x01, xds);
 	/* x display end */
 	xde = xds + mode->crtc_hdisplay;
 	wrptr = udl_set_register_lfsr16(wrptr, 0x03, xde);

 	/* y display start */
 	yds = mode->crtc_vtotal - mode->crtc_vsync_start;
 	wrptr = udl_set_register_lfsr16(wrptr, 0x05, yds);
 	/* y display end */
 	yde = yds + mode->crtc_vdisplay;
 	wrptr = udl_set_register_lfsr16(wrptr, 0x07, yde);

 	/* x end count is active + blanking - 1 */
 	wrptr = udl_set_register_lfsr16(wrptr, 0x09,
 					mode->crtc_htotal - 1);

 	/* libdlo hardcodes hsync start to 1 */
 	wrptr = udl_set_register_lfsr16(wrptr, 0x0B, 1);

 	/* hsync end is width of sync pulse + 1 */
 	wrptr = udl_set_register_lfsr16(wrptr, 0x0D,
 					mode->crtc_hsync_end - mode->crtc_hsync_start + 1);

 	/* hpixels is active pixels */
 	wrptr = udl_set_register_16(wrptr, 0x0F, mode->hdisplay);

 	/* yendcount is vertical active + vertical blanking */
 	yec = mode->crtc_vtotal;
 	wrptr = udl_set_register_lfsr16(wrptr, 0x11, yec);

 	/* libdlo hardcodes vsync start to 0 */
 	wrptr = udl_set_register_lfsr16(wrptr, 0x13, 0);

 	/* vsync end is width of vsync pulse */
 	wrptr = udl_set_register_lfsr16(wrptr, 0x15, mode->crtc_vsync_end - mode->crtc_vsync_start);

 	/* vpixels is active pixels */
 	wrptr = udl_set_register_16(wrptr, 0x17, mode->crtc_vdisplay);

 	wrptr = udl_set_register_16be(wrptr, 0x1B,
 				      mode->clock / 5);

 	return wrptr;
 }

 static char *udl_dummy_render(char *wrptr)
 {
 	*wrptr++ = 0xAF;
 	*wrptr++ = 0x6A; /* copy */
 	*wrptr++ = 0x00; /* from addr */
 	*wrptr++ = 0x00;
 	*wrptr++ = 0x00;
 	*wrptr++ = 0x01; /* one pixel */
 	*wrptr++ = 0x00; /* to address */
 	*wrptr++ = 0x00;
 	*wrptr++ = 0x00;
 	return wrptr;
 }

 static int udl_crtc_write_mode_to_hw(struct drm_crtc *crtc)
 {
 	struct drm_device *dev = crtc->dev;
 	struct udl_device *udl = dev->dev_private;
 	struct urb *urb;
 	char *buf;
 	int retval;

 	if (udl->mode_buf_len == 0) {
 		DRM_ERROR("No mode set\n");
 		return -EINVAL;
 	}

 	urb = udl_get_urb(dev);
 	if (!urb)
 		return -ENOMEM;

 	buf = (char *)urb->transfer_buffer;

 	memcpy(buf, udl->mode_buf, udl->mode_buf_len);
 	retval = udl_submit_urb(dev, urb, udl->mode_buf_len);
 	DRM_DEBUG("write mode info %d\n", udl->mode_buf_len);
 	return retval;
 }

 static long udl_log_cpp(unsigned int cpp)
 {
 	if (WARN_ON(!is_power_of_2(cpp)))
 		return -EINVAL;
 	return __ffs(cpp);
 }

 static int udl_aligned_damage_clip(struct drm_rect *clip, int x, int y,
 				   int width, int height)
 {
 	int x1, x2;

 	if (WARN_ON_ONCE(x < 0) ||
 	    WARN_ON_ONCE(y < 0) ||
 	    WARN_ON_ONCE(width < 0) ||
 	    WARN_ON_ONCE(height < 0))
 		return -EINVAL;

 	x1 = ALIGN_DOWN(x, sizeof(unsigned long));
 	x2 = ALIGN(width + (x - x1), sizeof(unsigned long)) + x1;

 	clip->x1 = x1;
 	clip->y1 = y;
 	clip->x2 = x2;
 	clip->y2 = y + height;

 	return 0;
 }

 int udl_handle_damage(struct drm_framebuffer *fb, int x, int y,
 		      int width, int height)
 {
 	struct drm_device *dev = fb->dev;
 	struct dma_buf_attachment *import_attach = fb->obj[0]->import_attach;
 	int i, ret, tmp_ret;
 	char *cmd;
 	struct urb *urb;
 	struct drm_rect clip;
 	int log_bpp;
 	void *vaddr;

 	ret = udl_log_cpp(fb->format->cpp[0]);
 	if (ret < 0)
 		return ret;
 	log_bpp = ret;

 	ret = udl_aligned_damage_clip(&clip, x, y, width, height);
 	if (ret)
 		return ret;
 	else if ((clip.x2 > fb->width) || (clip.y2 > fb->height))
 		return -EINVAL;

 	if (import_attach) {
 		ret = dma_buf_begin_cpu_access(import_attach->dmabuf,
 					       DMA_FROM_DEVICE);
 		if (ret)
 			return ret;
 	}

 	vaddr = drm_gem_shmem_vmap(fb->obj[0]);
 	if (IS_ERR(vaddr)) {
 		DRM_ERROR("failed to vmap fb\n");
 		goto out_dma_buf_end_cpu_access;
 	}

 	urb = udl_get_urb(dev);
 	if (!urb)
 		goto out_drm_gem_shmem_vunmap;
 	cmd = urb->transfer_buffer;

 	for (i = clip.y1; i < clip.y2; i++) {
 		const int line_offset = fb->pitches[0] * i;
 		const int byte_offset = line_offset + (clip.x1 << log_bpp);
 		const int dev_byte_offset = (fb->width * i + clip.x1) << log_bpp;
 		const int byte_width = (clip.x2 - clip.x1) << log_bpp;
 		ret = udl_render_hline(dev, log_bpp, &urb, (char *)vaddr,
 				       &cmd, byte_offset, dev_byte_offset,
 				       byte_width);
 		if (ret)
 			goto out_drm_gem_shmem_vunmap;
 	}

 	if (cmd > (char *)urb->transfer_buffer) {
 		/* Send partial buffer remaining before exiting */
 		int len;
 		if (cmd < (char *)urb->transfer_buffer + urb->transfer_buffer_length)
 			*cmd++ = 0xAF;
 		len = cmd - (char *)urb->transfer_buffer;
 		ret = udl_submit_urb(dev, urb, len);
 	} else {
 		udl_urb_completion(urb);
 	}

 	ret = 0;

 out_drm_gem_shmem_vunmap:
 	drm_gem_shmem_vunmap(fb->obj[0], vaddr);
 out_dma_buf_end_cpu_access:
 	if (import_attach) {
 		tmp_ret = dma_buf_end_cpu_access(import_attach->dmabuf,
 						 DMA_FROM_DEVICE);
 		if (tmp_ret && !ret)
 			ret = tmp_ret; /* only update ret if not set yet */
 	}

 	return ret;
 }

 /*
  * Simple display pipeline
  */

 static const uint32_t udl_simple_display_pipe_formats[] = {
 	DRM_FORMAT_RGB565,
 	DRM_FORMAT_XRGB8888,
 };

 static enum drm_mode_status
 udl_simple_display_pipe_mode_valid(struct drm_simple_display_pipe *pipe,
 				   const struct drm_display_mode *mode)
 {
 	return MODE_OK;
 }

 static void
 udl_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
 			       struct drm_crtc_state *crtc_state,
 			       struct drm_plane_state *plane_state)
 {
 	struct drm_crtc *crtc = &pipe->crtc;
 	struct drm_device *dev = crtc->dev;
 	struct drm_framebuffer *fb = plane_state->fb;
 	struct udl_device *udl = dev->dev_private;
 	struct drm_display_mode *mode = &crtc_state->mode;
 	char *buf;
 	char *wrptr;
 	int color_depth = UDL_COLOR_DEPTH_16BPP;

 	crtc_state->no_vblank = true;

 	buf = (char *)udl->mode_buf;

 	/* This first section has to do with setting the base address on the
 	 * controller associated with the display. There are 2 base
 	 * pointers, currently, we only use the 16 bpp segment.
 	 */
 	wrptr = udl_vidreg_lock(buf);
 	wrptr = udl_set_color_depth(wrptr, color_depth);
 	/* set base for 16bpp segment to 0 */
 	wrptr = udl_set_base16bpp(wrptr, 0);
 	/* set base for 8bpp segment to end of fb */
 	wrptr = udl_set_base8bpp(wrptr, 2 * mode->vdisplay * mode->hdisplay);

 	wrptr = udl_set_vid_cmds(wrptr, mode);
 	wrptr = udl_set_blank_mode(wrptr, UDL_BLANK_MODE_ON);
 	wrptr = udl_vidreg_unlock(wrptr);

 	wrptr = udl_dummy_render(wrptr);

 	udl->mode_buf_len = wrptr - buf;

 	udl_handle_damage(fb, 0, 0, fb->width, fb->height);

 	if (!crtc_state->mode_changed)
 		return;

 	/* enable display */
 	udl_crtc_write_mode_to_hw(crtc);
 }

 static void
 udl_simple_display_pipe_disable(struct drm_simple_display_pipe *pipe)
 {
 	struct drm_crtc *crtc = &pipe->crtc;
 	struct drm_device *dev = crtc->dev;
 	struct urb *urb;
 	char *buf;

 	urb = udl_get_urb(dev);
 	if (!urb)
 		return;

 	buf = (char *)urb->transfer_buffer;
 	buf = udl_vidreg_lock(buf);
 	buf = udl_set_blank_mode(buf, UDL_BLANK_MODE_POWERDOWN);
 	buf = udl_vidreg_unlock(buf);
 	buf = udl_dummy_render(buf);

 	udl_submit_urb(dev, urb, buf - (char *)urb->transfer_buffer);
 }

 static int
 udl_simple_display_pipe_check(struct drm_simple_display_pipe *pipe,
 			      struct drm_plane_state *plane_state,
 			      struct drm_crtc_state *crtc_state)
 {
 	return 0;
 }

 static void
 udl_simple_display_pipe_update(struct drm_simple_display_pipe *pipe,
 			       struct drm_plane_state *old_plane_state)
 {
 	struct drm_plane_state *state = pipe->plane.state;
 	struct drm_framebuffer *fb = state->fb;
 	struct drm_rect rect;

 	if (!fb)
 		return;

 	if (drm_atomic_helper_damage_merged(old_plane_state, state, &rect))
 		udl_handle_damage(fb, rect.x1, rect.y1, rect.x2 - rect.x1,
 				  rect.y2 - rect.y1);
 }

 static const
 struct drm_simple_display_pipe_funcs udl_simple_display_pipe_funcs = {
 	.mode_valid = udl_simple_display_pipe_mode_valid,
 	.enable = udl_simple_display_pipe_enable,
 	.disable = udl_simple_display_pipe_disable,
 	.check = udl_simple_display_pipe_check,
 	.update = udl_simple_display_pipe_update,
 	.prepare_fb = drm_gem_fb_simple_display_pipe_prepare_fb,
 };

 /*
  * Modesetting
  */

 static const struct drm_mode_config_funcs udl_mode_funcs = {
 	.fb_create = drm_gem_fb_create_with_dirty,
 	.atomic_check  = drm_atomic_helper_check,
 	.atomic_commit = drm_atomic_helper_commit,
 };

 int udl_modeset_init(struct drm_device *dev)
 {
 	size_t format_count = ARRAY_SIZE(udl_simple_display_pipe_formats);
 	struct udl_device *udl = dev->dev_private;
 	struct drm_connector *connector;
 	int ret;

 	drm_mode_config_init(dev);

 	dev->mode_config.min_width = 640;
 	dev->mode_config.min_height = 480;

 	dev->mode_config.max_width = 2048;
 	dev->mode_config.max_height = 2048;

 	dev->mode_config.prefer_shadow = 0;
 	dev->mode_config.preferred_depth = 16;

 	dev->mode_config.funcs = &udl_mode_funcs;

 	connector = udl_connector_init(dev);
 	if (IS_ERR(connector)) {
 		ret = PTR_ERR(connector);
 		goto err_drm_mode_config_cleanup;
 	}

 	format_count = ARRAY_SIZE(udl_simple_display_pipe_formats);

 	ret = drm_simple_display_pipe_init(dev, &udl->display_pipe,
 					   &udl_simple_display_pipe_funcs,
 					   udl_simple_display_pipe_formats,
 					   format_count, NULL, connector);
 	if (ret)
 		goto err_drm_mode_config_cleanup;

 	drm_mode_config_reset(dev);

 	return 0;

 err_drm_mode_config_cleanup:
 	drm_mode_config_cleanup(dev);
 	return ret;
 }

 void udl_modeset_cleanup(struct drm_device *dev)
 {
 	drm_mode_config_cleanup(dev);
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2012 Red Hat
	*
	* based in parts on udlfb.c:
	* Copyright (C) 2009 Roberto De Ioris <roberto@unbit.it>
	* Copyright (C) 2009 Jaya Kumar <jayakumar.lkml@gmail.com>
	* Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>

	*/

	#include <linux/dma-buf.h>

	#include <drm/drm_atomic_helper.h>
	#include <drm/drm_crtc_helper.h>
	#include <drm/drm_damage_helper.h>
	#include <drm/drm_fourcc.h>
	#include <drm/drm_gem_framebuffer_helper.h>
	#include <drm/drm_gem_shmem_helper.h>
	#include <drm/drm_modeset_helper_vtables.h>
	#include <drm/drm_vblank.h>

	#include "udl_drv.h"

	#define UDL_COLOR_DEPTH_16BPP 0

	/*
	* All DisplayLink bulk operations start with 0xAF, followed by specific code
	* All operations are written to buffers which then later get sent to device
	*/
	static char udl_set_register(char buf, u8 reg, u8 val)
	{
	*buf++ = 0xAF;
	*buf++ = 0x20;
	*buf++ = reg;
	*buf++ = val;
	return buf;
	}

	static char udl_vidreg_lock(char buf)
	{
	return udl_set_register(buf, 0xFF, 0x00);
	}

	static char udl_vidreg_unlock(char buf)
	{
	return udl_set_register(buf, 0xFF, 0xFF);
	}

	static char udl_set_blank_mode(char buf, u8 mode)
	{
	return udl_set_register(buf, UDL_REG_BLANK_MODE, mode);
	}

	static char udl_set_color_depth(char buf, u8 selection)
	{
	return udl_set_register(buf, 0x00, selection);
	}

	static char udl_set_base16bpp(char wrptr, u32 base)
	{
	/* the base pointer is 16 bits wide, 0x20 is hi byte. */
	wrptr = udl_set_register(wrptr, 0x20, base >> 16);
	wrptr = udl_set_register(wrptr, 0x21, base >> 8);
	return udl_set_register(wrptr, 0x22, base);
	}

	/*
	* DisplayLink HW has separate 16bpp and 8bpp framebuffers.
	* In 24bpp modes, the low 323 RGB bits go in the 8bpp framebuffer
	*/
	static char udl_set_base8bpp(char wrptr, u32 base)
	{
	wrptr = udl_set_register(wrptr, 0x26, base >> 16);
	wrptr = udl_set_register(wrptr, 0x27, base >> 8);
	return udl_set_register(wrptr, 0x28, base);
	}

	static char udl_set_register_16(char wrptr, u8 reg, u16 value)
	{
	wrptr = udl_set_register(wrptr, reg, value >> 8);
	return udl_set_register(wrptr, reg+1, value);
	}

	/*
	* This is kind of weird because the controller takes some
	* register values in a different byte order than other registers.
	*/
	static char udl_set_register_16be(char wrptr, u8 reg, u16 value)
	{
	wrptr = udl_set_register(wrptr, reg, value);
	return udl_set_register(wrptr, reg+1, value >> 8);
	}

	/*
	* LFSR is linear feedback shift register. The reason we have this is
	* because the display controller needs to minimize the clock depth of
	* various counters used in the display path. So this code reverses the
	* provided value into the lfsr16 value by counting backwards to get
	* the value that needs to be set in the hardware comparator to get the
	* same actual count. This makes sense once you read above a couple of
	* times and think about it from a hardware perspective.
	*/
	static u16 udl_lfsr16(u16 actual_count)
	{
	u32 lv = 0xFFFF; /* This is the lfsr value that the hw starts with */

	while (actual_count--) {
	lv = ((lv << 1) \|
	(((lv >> 15) ^ (lv >> 4) ^ (lv >> 2) ^ (lv >> 1)) & 1))
	& 0xFFFF;
	}

	return (u16) lv;
	}

	/*
	* This does LFSR conversion on the value that is to be written.
	* See LFSR explanation above for more detail.
	*/
	static char udl_set_register_lfsr16(char wrptr, u8 reg, u16 value)
	{
	return udl_set_register_16(wrptr, reg, udl_lfsr16(value));
	}

	/*
	* This takes a standard fbdev screeninfo struct and all of its monitor mode
	* details and converts them into the DisplayLink equivalent register commands.
	ERR(vreg(dev, 0x00, (color_depth == 16) ? 0 : 1));
	ERR(vreg_lfsr16(dev, 0x01, xDisplayStart));
	ERR(vreg_lfsr16(dev, 0x03, xDisplayEnd));
	ERR(vreg_lfsr16(dev, 0x05, yDisplayStart));
	ERR(vreg_lfsr16(dev, 0x07, yDisplayEnd));
	ERR(vreg_lfsr16(dev, 0x09, xEndCount));
	ERR(vreg_lfsr16(dev, 0x0B, hSyncStart));
	ERR(vreg_lfsr16(dev, 0x0D, hSyncEnd));
	ERR(vreg_big_endian(dev, 0x0F, hPixels));
	ERR(vreg_lfsr16(dev, 0x11, yEndCount));
	ERR(vreg_lfsr16(dev, 0x13, vSyncStart));
	ERR(vreg_lfsr16(dev, 0x15, vSyncEnd));
	ERR(vreg_big_endian(dev, 0x17, vPixels));
	ERR(vreg_little_endian(dev, 0x1B, pixelClock5KHz));

	ERR(vreg(dev, 0x1F, 0));

	ERR(vbuf(dev, WRITE_VIDREG_UNLOCK, DSIZEOF(WRITE_VIDREG_UNLOCK)));
	*/
	static char udl_set_vid_cmds(char wrptr, struct drm_display_mode *mode)
	{
	u16 xds, yds;
	u16 xde, yde;
	u16 yec;

	/* x display start */
	xds = mode->crtc_htotal - mode->crtc_hsync_start;
	wrptr = udl_set_register_lfsr16(wrptr, 0x01, xds);
	/* x display end */
	xde = xds + mode->crtc_hdisplay;
	wrptr = udl_set_register_lfsr16(wrptr, 0x03, xde);

	/* y display start */
	yds = mode->crtc_vtotal - mode->crtc_vsync_start;
	wrptr = udl_set_register_lfsr16(wrptr, 0x05, yds);
	/* y display end */
	yde = yds + mode->crtc_vdisplay;
	wrptr = udl_set_register_lfsr16(wrptr, 0x07, yde);

	/* x end count is active + blanking - 1 */
	wrptr = udl_set_register_lfsr16(wrptr, 0x09,
	mode->crtc_htotal - 1);

	/* libdlo hardcodes hsync start to 1 */
	wrptr = udl_set_register_lfsr16(wrptr, 0x0B, 1);

	/* hsync end is width of sync pulse + 1 */
	wrptr = udl_set_register_lfsr16(wrptr, 0x0D,
	mode->crtc_hsync_end - mode->crtc_hsync_start + 1);

	/* hpixels is active pixels */
	wrptr = udl_set_register_16(wrptr, 0x0F, mode->hdisplay);

	/* yendcount is vertical active + vertical blanking */
	yec = mode->crtc_vtotal;
	wrptr = udl_set_register_lfsr16(wrptr, 0x11, yec);

	/* libdlo hardcodes vsync start to 0 */
	wrptr = udl_set_register_lfsr16(wrptr, 0x13, 0);

	/* vsync end is width of vsync pulse */
	wrptr = udl_set_register_lfsr16(wrptr, 0x15, mode->crtc_vsync_end - mode->crtc_vsync_start);

	/* vpixels is active pixels */
	wrptr = udl_set_register_16(wrptr, 0x17, mode->crtc_vdisplay);

	wrptr = udl_set_register_16be(wrptr, 0x1B,
	mode->clock / 5);

	return wrptr;
	}

	static char udl_dummy_render(char wrptr)
	{
	*wrptr++ = 0xAF;
	wrptr++ = 0x6A; / copy */
	wrptr++ = 0x00; / from addr */
	*wrptr++ = 0x00;
	*wrptr++ = 0x00;
	wrptr++ = 0x01; / one pixel */
	wrptr++ = 0x00; / to address */
	*wrptr++ = 0x00;
	*wrptr++ = 0x00;
	return wrptr;
	}

	static int udl_crtc_write_mode_to_hw(struct drm_crtc *crtc)
	{
	struct drm_device *dev = crtc->dev;
	struct udl_device *udl = dev->dev_private;
	struct urb *urb;
	char *buf;
	int retval;

	if (udl->mode_buf_len == 0) {
	DRM_ERROR("No mode set\n");
	return -EINVAL;
	}

	urb = udl_get_urb(dev);
	if (!urb)
	return -ENOMEM;

	buf = (char *)urb->transfer_buffer;

	memcpy(buf, udl->mode_buf, udl->mode_buf_len);
	retval = udl_submit_urb(dev, urb, udl->mode_buf_len);
	DRM_DEBUG("write mode info %d\n", udl->mode_buf_len);
	return retval;
	}

	static long udl_log_cpp(unsigned int cpp)
	{
	if (WARN_ON(!is_power_of_2(cpp)))
	return -EINVAL;
	return __ffs(cpp);
	}

	static int udl_aligned_damage_clip(struct drm_rect *clip, int x, int y,
	int width, int height)
	{
	int x1, x2;

	if (WARN_ON_ONCE(x < 0) \|\|
	WARN_ON_ONCE(y < 0) \|\|
	WARN_ON_ONCE(width < 0) \|\|
	WARN_ON_ONCE(height < 0))
	return -EINVAL;

	x1 = ALIGN_DOWN(x, sizeof(unsigned long));
	x2 = ALIGN(width + (x - x1), sizeof(unsigned long)) + x1;

	clip->x1 = x1;
	clip->y1 = y;
	clip->x2 = x2;
	clip->y2 = y + height;

	return 0;
	}

	int udl_handle_damage(struct drm_framebuffer *fb, int x, int y,
	int width, int height)
	{
	struct drm_device *dev = fb->dev;
	struct dma_buf_attachment *import_attach = fb->obj[0]->import_attach;
	int i, ret, tmp_ret;
	char *cmd;
	struct urb *urb;
	struct drm_rect clip;
	int log_bpp;
	void *vaddr;

	ret = udl_log_cpp(fb->format->cpp[0]);
	if (ret < 0)
	return ret;
	log_bpp = ret;

	ret = udl_aligned_damage_clip(&clip, x, y, width, height);
	if (ret)
	return ret;
	else if ((clip.x2 > fb->width) \|\| (clip.y2 > fb->height))
	return -EINVAL;

	if (import_attach) {
	ret = dma_buf_begin_cpu_access(import_attach->dmabuf,
	DMA_FROM_DEVICE);
	if (ret)
	return ret;
	}

	vaddr = drm_gem_shmem_vmap(fb->obj[0]);
	if (IS_ERR(vaddr)) {
	DRM_ERROR("failed to vmap fb\n");
	goto out_dma_buf_end_cpu_access;
	}

	urb = udl_get_urb(dev);
	if (!urb)
	goto out_drm_gem_shmem_vunmap;
	cmd = urb->transfer_buffer;

	for (i = clip.y1; i < clip.y2; i++) {
	const int line_offset = fb->pitches[0] * i;
	const int byte_offset = line_offset + (clip.x1 << log_bpp);
	const int dev_byte_offset = (fb->width * i + clip.x1) << log_bpp;
	const int byte_width = (clip.x2 - clip.x1) << log_bpp;
	ret = udl_render_hline(dev, log_bpp, &urb, (char *)vaddr,
	&cmd, byte_offset, dev_byte_offset,
	byte_width);
	if (ret)
	goto out_drm_gem_shmem_vunmap;
	}

	if (cmd > (char *)urb->transfer_buffer) {
	/* Send partial buffer remaining before exiting */
	int len;
	if (cmd < (char *)urb->transfer_buffer + urb->transfer_buffer_length)
	*cmd++ = 0xAF;
	len = cmd - (char *)urb->transfer_buffer;
	ret = udl_submit_urb(dev, urb, len);
	} else {
	udl_urb_completion(urb);
	}

	ret = 0;

	out_drm_gem_shmem_vunmap:
	drm_gem_shmem_vunmap(fb->obj[0], vaddr);
	out_dma_buf_end_cpu_access:
	if (import_attach) {
	tmp_ret = dma_buf_end_cpu_access(import_attach->dmabuf,
	DMA_FROM_DEVICE);
	if (tmp_ret && !ret)
	ret = tmp_ret; /* only update ret if not set yet */
	}

	return ret;
	}

	/*
	* Simple display pipeline
	*/

	static const uint32_t udl_simple_display_pipe_formats[] = {
	DRM_FORMAT_RGB565,
	DRM_FORMAT_XRGB8888,
	};

	static enum drm_mode_status
	udl_simple_display_pipe_mode_valid(struct drm_simple_display_pipe *pipe,
	const struct drm_display_mode *mode)
	{
	return MODE_OK;
	}

	static void
	udl_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
	struct drm_crtc_state *crtc_state,
	struct drm_plane_state *plane_state)
	{
	struct drm_crtc *crtc = &pipe->crtc;
	struct drm_device *dev = crtc->dev;
	struct drm_framebuffer *fb = plane_state->fb;
	struct udl_device *udl = dev->dev_private;
	struct drm_display_mode *mode = &crtc_state->mode;
	char *buf;
	char *wrptr;
	int color_depth = UDL_COLOR_DEPTH_16BPP;

	crtc_state->no_vblank = true;

	buf = (char *)udl->mode_buf;

	/* This first section has to do with setting the base address on the
	* controller associated with the display. There are 2 base
	* pointers, currently, we only use the 16 bpp segment.
	*/
	wrptr = udl_vidreg_lock(buf);
	wrptr = udl_set_color_depth(wrptr, color_depth);
	/* set base for 16bpp segment to 0 */
	wrptr = udl_set_base16bpp(wrptr, 0);
	/* set base for 8bpp segment to end of fb */
	wrptr = udl_set_base8bpp(wrptr, 2 * mode->vdisplay * mode->hdisplay);

	wrptr = udl_set_vid_cmds(wrptr, mode);
	wrptr = udl_set_blank_mode(wrptr, UDL_BLANK_MODE_ON);
	wrptr = udl_vidreg_unlock(wrptr);

	wrptr = udl_dummy_render(wrptr);

	udl->mode_buf_len = wrptr - buf;

	udl_handle_damage(fb, 0, 0, fb->width, fb->height);

	if (!crtc_state->mode_changed)
	return;

	/* enable display */
	udl_crtc_write_mode_to_hw(crtc);
	}

	static void
	udl_simple_display_pipe_disable(struct drm_simple_display_pipe *pipe)
	{
	struct drm_crtc *crtc = &pipe->crtc;
	struct drm_device *dev = crtc->dev;
	struct urb *urb;
	char *buf;

	urb = udl_get_urb(dev);
	if (!urb)
	return;

	buf = (char *)urb->transfer_buffer;
	buf = udl_vidreg_lock(buf);
	buf = udl_set_blank_mode(buf, UDL_BLANK_MODE_POWERDOWN);
	buf = udl_vidreg_unlock(buf);
	buf = udl_dummy_render(buf);

	udl_submit_urb(dev, urb, buf - (char *)urb->transfer_buffer);
	}

	static int
	udl_simple_display_pipe_check(struct drm_simple_display_pipe *pipe,
	struct drm_plane_state *plane_state,
	struct drm_crtc_state *crtc_state)
	{
	return 0;
	}

	static void
	udl_simple_display_pipe_update(struct drm_simple_display_pipe *pipe,
	struct drm_plane_state *old_plane_state)
	{
	struct drm_plane_state *state = pipe->plane.state;
	struct drm_framebuffer *fb = state->fb;
	struct drm_rect rect;

	if (!fb)
	return;

	if (drm_atomic_helper_damage_merged(old_plane_state, state, &rect))
	udl_handle_damage(fb, rect.x1, rect.y1, rect.x2 - rect.x1,
	rect.y2 - rect.y1);
	}

	static const
	struct drm_simple_display_pipe_funcs udl_simple_display_pipe_funcs = {
	.mode_valid = udl_simple_display_pipe_mode_valid,
	.enable = udl_simple_display_pipe_enable,
	.disable = udl_simple_display_pipe_disable,
	.check = udl_simple_display_pipe_check,
	.update = udl_simple_display_pipe_update,
	.prepare_fb = drm_gem_fb_simple_display_pipe_prepare_fb,
	};

	/*
	* Modesetting
	*/

	static const struct drm_mode_config_funcs udl_mode_funcs = {
	.fb_create = drm_gem_fb_create_with_dirty,
	.atomic_check = drm_atomic_helper_check,
	.atomic_commit = drm_atomic_helper_commit,
	};

	int udl_modeset_init(struct drm_device *dev)
	{
	size_t format_count = ARRAY_SIZE(udl_simple_display_pipe_formats);
	struct udl_device *udl = dev->dev_private;
	struct drm_connector *connector;
	int ret;

	drm_mode_config_init(dev);

	dev->mode_config.min_width = 640;
	dev->mode_config.min_height = 480;

	dev->mode_config.max_width = 2048;
	dev->mode_config.max_height = 2048;

	dev->mode_config.prefer_shadow = 0;
	dev->mode_config.preferred_depth = 16;

	dev->mode_config.funcs = &udl_mode_funcs;

	connector = udl_connector_init(dev);
	if (IS_ERR(connector)) {
	ret = PTR_ERR(connector);
	goto err_drm_mode_config_cleanup;
	}

	format_count = ARRAY_SIZE(udl_simple_display_pipe_formats);

	ret = drm_simple_display_pipe_init(dev, &udl->display_pipe,
	&udl_simple_display_pipe_funcs,
	udl_simple_display_pipe_formats,
	format_count, NULL, connector);
	if (ret)
	goto err_drm_mode_config_cleanup;

	drm_mode_config_reset(dev);

	return 0;

	err_drm_mode_config_cleanup:
	drm_mode_config_cleanup(dev);
	return ret;
	}

	void udl_modeset_cleanup(struct drm_device *dev)
	{
	drm_mode_config_cleanup(dev);
	}