path: root/0301-revert-garbage-collect-fbdev-scrolling-acceleration.patch

--- b/Documentation/gpu/todo.rst
+++ a/Documentation/gpu/todo.rst
@@ -314,19 +314,16 @@
 Garbage collect fbdev scrolling acceleration
 --------------------------------------------
 
+Scroll acceleration is disabled in fbcon by hard-wiring p->scrollmode =
+SCROLL_REDRAW. There's a ton of code this will allow us to remove:
-Scroll acceleration has been disabled in fbcon. Now it works as the old
-SCROLL_REDRAW mode. A ton of code was removed in fbcon.c and the hook bmove was
-removed from fbcon_ops.
-Remaining tasks:
 
+- lots of code in fbcon.c
+
+- a bunch of the hooks in fbcon_ops, maybe the remaining hooks could be called
-- a bunch of the hooks in fbcon_ops could be removed or simplified by calling
   directly instead of the function table (with a switch on p->rotate)
 
 - fb_copyarea is unused after this, and can be deleted from all drivers
 
-- after that, fb_copyarea can be deleted from fb_ops in include/linux/fb.h as
-  well as cfb_copyarea
-
 Note that not all acceleration code can be deleted, since clearing and cursor
 support is still accelerated, which might be good candidates for further
 deletion projects.
--- b/drivers/video/fbdev/core/bitblit.c
+++ a/drivers/video/fbdev/core/bitblit.c
@@ -43,6 +43,21 @@
 	}
 }
 
+static void bit_bmove(struct vc_data *vc, struct fb_info *info, int sy,
+		      int sx, int dy, int dx, int height, int width)
+{
+	struct fb_copyarea area;
+
+	area.sx = sx * vc->vc_font.width;
+	area.sy = sy * vc->vc_font.height;
+	area.dx = dx * vc->vc_font.width;
+	area.dy = dy * vc->vc_font.height;
+	area.height = height * vc->vc_font.height;
+	area.width = width * vc->vc_font.width;
+
+	info->fbops->fb_copyarea(info, &area);
+}
+
 static void bit_clear(struct vc_data *vc, struct fb_info *info, int sy,
 		      int sx, int height, int width)
 {
@@ -378,6 +393,7 @@
 
 void fbcon_set_bitops(struct fbcon_ops *ops)
 {
+	ops->bmove = bit_bmove;
 	ops->clear = bit_clear;
 	ops->putcs = bit_putcs;
 	ops->clear_margins = bit_clear_margins;
--- b/drivers/video/fbdev/core/fbcon.c
+++ a/drivers/video/fbdev/core/fbcon.c
@@ -173,6 +173,8 @@
 			int count, int ypos, int xpos);
 static void fbcon_clear_margins(struct vc_data *vc, int bottom_only);
 static void fbcon_cursor(struct vc_data *vc, int mode);
+static void fbcon_bmove(struct vc_data *vc, int sy, int sx, int dy, int dx,
+			int height, int width);
 static int fbcon_switch(struct vc_data *vc);
 static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch);
 static void fbcon_set_palette(struct vc_data *vc, const unsigned char *table);
@@ -180,8 +182,16 @@
 /*
  *  Internal routines
  */
+static __inline__ void ywrap_up(struct vc_data *vc, int count);
+static __inline__ void ywrap_down(struct vc_data *vc, int count);
+static __inline__ void ypan_up(struct vc_data *vc, int count);
+static __inline__ void ypan_down(struct vc_data *vc, int count);
+static void fbcon_bmove_rec(struct vc_data *vc, struct fbcon_display *p, int sy, int sx,
+			    int dy, int dx, int height, int width, u_int y_break);
 static void fbcon_set_disp(struct fb_info *info, struct fb_var_screeninfo *var,
 			   int unit);
+static void fbcon_redraw_move(struct vc_data *vc, struct fbcon_display *p,
+			      int line, int count, int dy);
 static void fbcon_modechanged(struct fb_info *info);
 static void fbcon_set_all_vcs(struct fb_info *info);
 static void fbcon_start(void);
@@ -1125,6 +1135,14 @@
 
 	ops->graphics = 0;
 
+	/*
+	 * No more hw acceleration for fbcon.
+	 *
+	 * FIXME: Garbage collect all the now dead code after sufficient time
+	 * has passed.
+	 */
+	p->scrollmode = SCROLL_REDRAW;
+
 	/*
 	 *  ++guenther: console.c:vc_allocate() relies on initializing
 	 *  vc_{cols,rows}, but we must not set those if we are only
@@ -1211,13 +1229,14 @@
  *  This system is now divided into two levels because of complications
  *  caused by hardware scrolling. Top level functions:
  *
+ *	fbcon_bmove(), fbcon_clear(), fbcon_putc(), fbcon_clear_margins()
- *	fbcon_clear(), fbcon_putc(), fbcon_clear_margins()
  *
  *  handles y values in range [0, scr_height-1] that correspond to real
  *  screen positions. y_wrap shift means that first line of bitmap may be
  *  anywhere on this display. These functions convert lineoffsets to
  *  bitmap offsets and deal with the wrap-around case by splitting blits.
  *
+ *	fbcon_bmove_physical_8()    -- These functions fast implementations
  *	fbcon_clear_physical_8()    -- of original fbcon_XXX fns.
  *	fbcon_putc_physical_8()	    -- (font width != 8) may be added later
  *
@@ -1390,6 +1409,224 @@
 	}
 }
 
+static __inline__ void ywrap_up(struct vc_data *vc, int count)
+{
+	struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+	struct fbcon_ops *ops = info->fbcon_par;
+	struct fbcon_display *p = &fb_display[vc->vc_num];
+	
+	p->yscroll += count;
+	if (p->yscroll >= p->vrows)	/* Deal with wrap */
+		p->yscroll -= p->vrows;
+	ops->var.xoffset = 0;
+	ops->var.yoffset = p->yscroll * vc->vc_font.height;
+	ops->var.vmode |= FB_VMODE_YWRAP;
+	ops->update_start(info);
+	scrollback_max += count;
+	if (scrollback_max > scrollback_phys_max)
+		scrollback_max = scrollback_phys_max;
+	scrollback_current = 0;
+}
+
+static __inline__ void ywrap_down(struct vc_data *vc, int count)
+{
+	struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+	struct fbcon_ops *ops = info->fbcon_par;
+	struct fbcon_display *p = &fb_display[vc->vc_num];
+	
+	p->yscroll -= count;
+	if (p->yscroll < 0)	/* Deal with wrap */
+		p->yscroll += p->vrows;
+	ops->var.xoffset = 0;
+	ops->var.yoffset = p->yscroll * vc->vc_font.height;
+	ops->var.vmode |= FB_VMODE_YWRAP;
+	ops->update_start(info);
+	scrollback_max -= count;
+	if (scrollback_max < 0)
+		scrollback_max = 0;
+	scrollback_current = 0;
+}
+
+static __inline__ void ypan_up(struct vc_data *vc, int count)
+{
+	struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+	struct fbcon_display *p = &fb_display[vc->vc_num];
+	struct fbcon_ops *ops = info->fbcon_par;
+
+	p->yscroll += count;
+	if (p->yscroll > p->vrows - vc->vc_rows) {
+		ops->bmove(vc, info, p->vrows - vc->vc_rows,
+			    0, 0, 0, vc->vc_rows, vc->vc_cols);
+		p->yscroll -= p->vrows - vc->vc_rows;
+	}
+
+	ops->var.xoffset = 0;
+	ops->var.yoffset = p->yscroll * vc->vc_font.height;
+	ops->var.vmode &= ~FB_VMODE_YWRAP;
+	ops->update_start(info);
+	fbcon_clear_margins(vc, 1);
+	scrollback_max += count;
+	if (scrollback_max > scrollback_phys_max)
+		scrollback_max = scrollback_phys_max;
+	scrollback_current = 0;
+}
+
+static __inline__ void ypan_up_redraw(struct vc_data *vc, int t, int count)
+{
+	struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+	struct fbcon_ops *ops = info->fbcon_par;
+	struct fbcon_display *p = &fb_display[vc->vc_num];
+
+	p->yscroll += count;
+
+	if (p->yscroll > p->vrows - vc->vc_rows) {
+		p->yscroll -= p->vrows - vc->vc_rows;
+		fbcon_redraw_move(vc, p, t + count, vc->vc_rows - count, t);
+	}
+
+	ops->var.xoffset = 0;
+	ops->var.yoffset = p->yscroll * vc->vc_font.height;
+	ops->var.vmode &= ~FB_VMODE_YWRAP;
+	ops->update_start(info);
+	fbcon_clear_margins(vc, 1);
+	scrollback_max += count;
+	if (scrollback_max > scrollback_phys_max)
+		scrollback_max = scrollback_phys_max;
+	scrollback_current = 0;
+}
+
+static __inline__ void ypan_down(struct vc_data *vc, int count)
+{
+	struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+	struct fbcon_display *p = &fb_display[vc->vc_num];
+	struct fbcon_ops *ops = info->fbcon_par;
+	
+	p->yscroll -= count;
+	if (p->yscroll < 0) {
+		ops->bmove(vc, info, 0, 0, p->vrows - vc->vc_rows,
+			    0, vc->vc_rows, vc->vc_cols);
+		p->yscroll += p->vrows - vc->vc_rows;
+	}
+
+	ops->var.xoffset = 0;
+	ops->var.yoffset = p->yscroll * vc->vc_font.height;
+	ops->var.vmode &= ~FB_VMODE_YWRAP;
+	ops->update_start(info);
+	fbcon_clear_margins(vc, 1);
+	scrollback_max -= count;
+	if (scrollback_max < 0)
+		scrollback_max = 0;
+	scrollback_current = 0;
+}
+
+static __inline__ void ypan_down_redraw(struct vc_data *vc, int t, int count)
+{
+	struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+	struct fbcon_ops *ops = info->fbcon_par;
+	struct fbcon_display *p = &fb_display[vc->vc_num];
+
+	p->yscroll -= count;
+
+	if (p->yscroll < 0) {
+		p->yscroll += p->vrows - vc->vc_rows;
+		fbcon_redraw_move(vc, p, t, vc->vc_rows - count, t + count);
+	}
+
+	ops->var.xoffset = 0;
+	ops->var.yoffset = p->yscroll * vc->vc_font.height;
+	ops->var.vmode &= ~FB_VMODE_YWRAP;
+	ops->update_start(info);
+	fbcon_clear_margins(vc, 1);
+	scrollback_max -= count;
+	if (scrollback_max < 0)
+		scrollback_max = 0;
+	scrollback_current = 0;
+}
+
+static void fbcon_redraw_move(struct vc_data *vc, struct fbcon_display *p,
+			      int line, int count, int dy)
+{
+	unsigned short *s = (unsigned short *)
+		(vc->vc_origin + vc->vc_size_row * line);
+
+	while (count--) {
+		unsigned short *start = s;
+		unsigned short *le = advance_row(s, 1);
+		unsigned short c;
+		int x = 0;
+		unsigned short attr = 1;
+
+		do {
+			c = scr_readw(s);
+			if (attr != (c & 0xff00)) {
+				attr = c & 0xff00;
+				if (s > start) {
+					fbcon_putcs(vc, start, s - start,
+						    dy, x);
+					x += s - start;
+					start = s;
+				}
+			}
+			console_conditional_schedule();
+			s++;
+		} while (s < le);
+		if (s > start)
+			fbcon_putcs(vc, start, s - start, dy, x);
+		console_conditional_schedule();
+		dy++;
+	}
+}
+
+static void fbcon_redraw_blit(struct vc_data *vc, struct fb_info *info,
+			struct fbcon_display *p, int line, int count, int ycount)
+{
+	int offset = ycount * vc->vc_cols;
+	unsigned short *d = (unsigned short *)
+	    (vc->vc_origin + vc->vc_size_row * line);
+	unsigned short *s = d + offset;
+	struct fbcon_ops *ops = info->fbcon_par;
+
+	while (count--) {
+		unsigned short *start = s;
+		unsigned short *le = advance_row(s, 1);
+		unsigned short c;
+		int x = 0;
+
+		do {
+			c = scr_readw(s);
+
+			if (c == scr_readw(d)) {
+				if (s > start) {
+					ops->bmove(vc, info, line + ycount, x,
+						   line, x, 1, s-start);
+					x += s - start + 1;
+					start = s + 1;
+				} else {
+					x++;
+					start++;
+				}
+			}
+
+			scr_writew(c, d);
+			console_conditional_schedule();
+			s++;
+			d++;
+		} while (s < le);
+		if (s > start)
+			ops->bmove(vc, info, line + ycount, x, line, x, 1,
+				   s-start);
+		console_conditional_schedule();
+		if (ycount > 0)
+			line++;
+		else {
+			line--;
+			/* NOTE: We subtract two lines from these pointers */
+			s -= vc->vc_size_row;
+			d -= vc->vc_size_row;
+		}
+	}
+}
+
 static void fbcon_redraw(struct vc_data *vc, struct fbcon_display *p,
 			 int line, int count, int offset)
 {
@@ -1450,6 +1687,7 @@
 {
 	struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
 	struct fbcon_display *p = &fb_display[vc->vc_num];
+	int scroll_partial = info->flags & FBINFO_PARTIAL_PAN_OK;
 
 	if (fbcon_is_inactive(vc, info))
 		return true;
@@ -1466,32 +1704,249 @@
 	case SM_UP:
 		if (count > vc->vc_rows)	/* Maximum realistic size */
 			count = vc->vc_rows;
+		if (logo_shown >= 0)
+			goto redraw_up;
+		switch (p->scrollmode) {
+		case SCROLL_MOVE:
+			fbcon_redraw_blit(vc, info, p, t, b - t - count,
+				     count);
+			fbcon_clear(vc, b - count, 0, count, vc->vc_cols);
+			scr_memsetw((unsigned short *) (vc->vc_origin +
+							vc->vc_size_row *
+							(b - count)),
+				    vc->vc_video_erase_char,
+				    vc->vc_size_row * count);
+			return true;
+
+		case SCROLL_WRAP_MOVE:
+			if (b - t - count > 3 * vc->vc_rows >> 2) {
+				if (t > 0)
+					fbcon_bmove(vc, 0, 0, count, 0, t,
+						    vc->vc_cols);
+				ywrap_up(vc, count);
+				if (vc->vc_rows - b > 0)
+					fbcon_bmove(vc, b - count, 0, b, 0,
+						    vc->vc_rows - b,
+						    vc->vc_cols);
+			} else if (info->flags & FBINFO_READS_FAST)
+				fbcon_bmove(vc, t + count, 0, t, 0,
+					    b - t - count, vc->vc_cols);
+			else
+				goto redraw_up;
+			fbcon_clear(vc, b - count, 0, count, vc->vc_cols);
+			break;
+
+		case SCROLL_PAN_REDRAW:
+			if ((p->yscroll + count <=
+			     2 * (p->vrows - vc->vc_rows))
+			    && ((!scroll_partial && (b - t == vc->vc_rows))
+				|| (scroll_partial
+				    && (b - t - count >
+					3 * vc->vc_rows >> 2)))) {
+				if (t > 0)
+					fbcon_redraw_move(vc, p, 0, t, count);
+				ypan_up_redraw(vc, t, count);
+				if (vc->vc_rows - b > 0)
+					fbcon_redraw_move(vc, p, b,
+							  vc->vc_rows - b, b);
+			} else
+				fbcon_redraw_move(vc, p, t + count, b - t - count, t);
+			fbcon_clear(vc, b - count, 0, count, vc->vc_cols);
+			break;
+
+		case SCROLL_PAN_MOVE:
+			if ((p->yscroll + count <=
+			     2 * (p->vrows - vc->vc_rows))
+			    && ((!scroll_partial && (b - t == vc->vc_rows))
+				|| (scroll_partial
+				    && (b - t - count >
+					3 * vc->vc_rows >> 2)))) {
+				if (t > 0)
+					fbcon_bmove(vc, 0, 0, count, 0, t,
+						    vc->vc_cols);
+				ypan_up(vc, count);
+				if (vc->vc_rows - b > 0)
+					fbcon_bmove(vc, b - count, 0, b, 0,
+						    vc->vc_rows - b,
+						    vc->vc_cols);
+			} else if (info->flags & FBINFO_READS_FAST)
+				fbcon_bmove(vc, t + count, 0, t, 0,
+					    b - t - count, vc->vc_cols);
+			else
+				goto redraw_up;
+			fbcon_clear(vc, b - count, 0, count, vc->vc_cols);
+			break;
+
+		case SCROLL_REDRAW:
+		      redraw_up:
+			fbcon_redraw(vc, p, t, b - t - count,
+				     count * vc->vc_cols);
+			fbcon_clear(vc, b - count, 0, count, vc->vc_cols);
+			scr_memsetw((unsigned short *) (vc->vc_origin +
+							vc->vc_size_row *
+							(b - count)),
+				    vc->vc_video_erase_char,
+				    vc->vc_size_row * count);
+			return true;
+		}
+		break;
-		fbcon_redraw(vc, p, t, b - t - count,
-			     count * vc->vc_cols);
-		fbcon_clear(vc, b - count, 0, count, vc->vc_cols);
-		scr_memsetw((unsigned short *) (vc->vc_origin +
-						vc->vc_size_row *
-						(b - count)),
-			    vc->vc_video_erase_char,
-			    vc->vc_size_row * count);
-		return true;
 
 	case SM_DOWN:
 		if (count > vc->vc_rows)	/* Maximum realistic size */
 			count = vc->vc_rows;
+		if (logo_shown >= 0)
+			goto redraw_down;
+		switch (p->scrollmode) {
+		case SCROLL_MOVE:
+			fbcon_redraw_blit(vc, info, p, b - 1, b - t - count,
+				     -count);
+			fbcon_clear(vc, t, 0, count, vc->vc_cols);
+			scr_memsetw((unsigned short *) (vc->vc_origin +
+							vc->vc_size_row *
+							t),
+				    vc->vc_video_erase_char,
+				    vc->vc_size_row * count);
+			return true;
+
+		case SCROLL_WRAP_MOVE:
+			if (b - t - count > 3 * vc->vc_rows >> 2) {
+				if (vc->vc_rows - b > 0)
+					fbcon_bmove(vc, b, 0, b - count, 0,
+						    vc->vc_rows - b,
+						    vc->vc_cols);
+				ywrap_down(vc, count);
+				if (t > 0)
+					fbcon_bmove(vc, count, 0, 0, 0, t,
+						    vc->vc_cols);
+			} else if (info->flags & FBINFO_READS_FAST)
+				fbcon_bmove(vc, t, 0, t + count, 0,
+					    b - t - count, vc->vc_cols);
+			else
+				goto redraw_down;
+			fbcon_clear(vc, t, 0, count, vc->vc_cols);
+			break;
+
+		case SCROLL_PAN_MOVE:
+			if ((count - p->yscroll <= p->vrows - vc->vc_rows)
+			    && ((!scroll_partial && (b - t == vc->vc_rows))
+				|| (scroll_partial
+				    && (b - t - count >
+					3 * vc->vc_rows >> 2)))) {
+				if (vc->vc_rows - b > 0)
+					fbcon_bmove(vc, b, 0, b - count, 0,
+						    vc->vc_rows - b,
+						    vc->vc_cols);
+				ypan_down(vc, count);
+				if (t > 0)
+					fbcon_bmove(vc, count, 0, 0, 0, t,
+						    vc->vc_cols);
+			} else if (info->flags & FBINFO_READS_FAST)
+				fbcon_bmove(vc, t, 0, t + count, 0,
+					    b - t - count, vc->vc_cols);
+			else
+				goto redraw_down;
+			fbcon_clear(vc, t, 0, count, vc->vc_cols);
+			break;
+
+		case SCROLL_PAN_REDRAW:
+			if ((count - p->yscroll <= p->vrows - vc->vc_rows)
+			    && ((!scroll_partial && (b - t == vc->vc_rows))
+				|| (scroll_partial
+				    && (b - t - count >
+					3 * vc->vc_rows >> 2)))) {
+				if (vc->vc_rows - b > 0)
+					fbcon_redraw_move(vc, p, b, vc->vc_rows - b,
+							  b - count);
+				ypan_down_redraw(vc, t, count);
+				if (t > 0)
+					fbcon_redraw_move(vc, p, count, t, 0);
+			} else
+				fbcon_redraw_move(vc, p, t, b - t - count, t + count);
+			fbcon_clear(vc, t, 0, count, vc->vc_cols);
+			break;
+
+		case SCROLL_REDRAW:
+		      redraw_down:
+			fbcon_redraw(vc, p, b - 1, b - t - count,
+				     -count * vc->vc_cols);
+			fbcon_clear(vc, t, 0, count, vc->vc_cols);
+			scr_memsetw((unsigned short *) (vc->vc_origin +
+							vc->vc_size_row *
+							t),
+				    vc->vc_video_erase_char,
+				    vc->vc_size_row * count);
+			return true;
+		}
-		fbcon_redraw(vc, p, b - 1, b - t - count,
-			     -count * vc->vc_cols);
-		fbcon_clear(vc, t, 0, count, vc->vc_cols);
-		scr_memsetw((unsigned short *) (vc->vc_origin +
-						vc->vc_size_row *
-						t),
-			    vc->vc_video_erase_char,
-			    vc->vc_size_row * count);
-		return true;
 	}
 	return false;
 }
 
+
+static void fbcon_bmove(struct vc_data *vc, int sy, int sx, int dy, int dx,
+			int height, int width)
+{
+	struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+	struct fbcon_display *p = &fb_display[vc->vc_num];
+	
+	if (fbcon_is_inactive(vc, info))
+		return;
+
+	if (!width || !height)
+		return;
+
+	/*  Split blits that cross physical y_wrap case.
+	 *  Pathological case involves 4 blits, better to use recursive
+	 *  code rather than unrolled case
+	 *
+	 *  Recursive invocations don't need to erase the cursor over and
+	 *  over again, so we use fbcon_bmove_rec()
+	 */
+	fbcon_bmove_rec(vc, p, sy, sx, dy, dx, height, width,
+			p->vrows - p->yscroll);
+}
+
+static void fbcon_bmove_rec(struct vc_data *vc, struct fbcon_display *p, int sy, int sx,
+			    int dy, int dx, int height, int width, u_int y_break)
+{
+	struct fb_info *info = registered_fb[con2fb_map[vc->vc_num]];
+	struct fbcon_ops *ops = info->fbcon_par;
+	u_int b;
+
+	if (sy < y_break && sy + height > y_break) {
+		b = y_break - sy;
+		if (dy < sy) {	/* Avoid trashing self */
+			fbcon_bmove_rec(vc, p, sy, sx, dy, dx, b, width,
+					y_break);
+			fbcon_bmove_rec(vc, p, sy + b, sx, dy + b, dx,
+					height - b, width, y_break);
+		} else {
+			fbcon_bmove_rec(vc, p, sy + b, sx, dy + b, dx,
+					height - b, width, y_break);
+			fbcon_bmove_rec(vc, p, sy, sx, dy, dx, b, width,
+					y_break);
+		}
+		return;
+	}
+
+	if (dy < y_break && dy + height > y_break) {
+		b = y_break - dy;
+		if (dy < sy) {	/* Avoid trashing self */
+			fbcon_bmove_rec(vc, p, sy, sx, dy, dx, b, width,
+					y_break);
+			fbcon_bmove_rec(vc, p, sy + b, sx, dy + b, dx,
+					height - b, width, y_break);
+		} else {
+			fbcon_bmove_rec(vc, p, sy + b, sx, dy + b, dx,
+					height - b, width, y_break);
+			fbcon_bmove_rec(vc, p, sy, sx, dy, dx, b, width,
+					y_break);
+		}
+		return;
+	}
+	ops->bmove(vc, info, real_y(p, sy), sx, real_y(p, dy), dx,
+		   height, width);
+}
+
 static void updatescrollmode(struct fbcon_display *p,
 					struct fb_info *info,
 					struct vc_data *vc)
@@ -1664,7 +2119,21 @@
 
 	updatescrollmode(p, info, vc);
 
+	switch (p->scrollmode) {
+	case SCROLL_WRAP_MOVE:
+		scrollback_phys_max = p->vrows - vc->vc_rows;
+		break;
+	case SCROLL_PAN_MOVE:
+	case SCROLL_PAN_REDRAW:
+		scrollback_phys_max = p->vrows - 2 * vc->vc_rows;
+		if (scrollback_phys_max < 0)
+			scrollback_phys_max = 0;
+		break;
+	default:
+		scrollback_phys_max = 0;
+		break;
+	}
+
-	scrollback_phys_max = 0;
 	scrollback_max = 0;
 	scrollback_current = 0;
 
--- b/drivers/video/fbdev/core/fbcon.h
+++ a/drivers/video/fbdev/core/fbcon.h
@@ -29,6 +29,7 @@
     /* Filled in by the low-level console driver */
     const u_char *fontdata;
     int userfont;                   /* != 0 if fontdata kmalloc()ed */
+    u_short scrollmode;             /* Scroll Method */
     u_short inverse;                /* != 0 text black on white as default */
     short yscroll;                  /* Hardware scrolling */
     int vrows;                      /* number of virtual rows */
@@ -51,6 +52,8 @@
 };
 
 struct fbcon_ops {
+	void (*bmove)(struct vc_data *vc, struct fb_info *info, int sy,
+		      int sx, int dy, int dx, int height, int width);
 	void (*clear)(struct vc_data *vc, struct fb_info *info, int sy,
 		      int sx, int height, int width);
 	void (*putcs)(struct vc_data *vc, struct fb_info *info,
@@ -149,6 +152,62 @@
 #define attr_bgcol_ec(bgshift, vc, info) attr_col_ec(bgshift, vc, info, 0)
 #define attr_fgcol_ec(fgshift, vc, info) attr_col_ec(fgshift, vc, info, 1)
 
+    /*
+     *  Scroll Method
+     */
+     
+/* There are several methods fbcon can use to move text around the screen:
+ *
+ *                     Operation   Pan    Wrap
+ *---------------------------------------------
+ * SCROLL_MOVE         copyarea    No     No
+ * SCROLL_PAN_MOVE     copyarea    Yes    No
+ * SCROLL_WRAP_MOVE    copyarea    No     Yes
+ * SCROLL_REDRAW       imageblit   No     No
+ * SCROLL_PAN_REDRAW   imageblit   Yes    No
+ * SCROLL_WRAP_REDRAW  imageblit   No     Yes
+ *
+ * (SCROLL_WRAP_REDRAW is not implemented yet)
+ *
+ * In general, fbcon will choose the best scrolling
+ * method based on the rule below:
+ *
+ * Pan/Wrap > accel imageblit > accel copyarea >
+ * soft imageblit > (soft copyarea)
+ *
+ * Exception to the rule: Pan + accel copyarea is
+ * preferred over Pan + accel imageblit.
+ *
+ * The above is typical for PCI/AGP cards. Unless
+ * overridden, fbcon will never use soft copyarea.
+ *
+ * If you need to override the above rule, set the
+ * appropriate flags in fb_info->flags.  For example,
+ * to prefer copyarea over imageblit, set
+ * FBINFO_READS_FAST.
+ *
+ * Other notes:
+ * + use the hardware engine to move the text
+ *    (hw-accelerated copyarea() and fillrect())
+ * + use hardware-supported panning on a large virtual screen
+ * + amifb can not only pan, but also wrap the display by N lines
+ *    (i.e. visible line i = physical line (i+N) % yres).
+ * + read what's already rendered on the screen and
+ *     write it in a different place (this is cfb_copyarea())
+ * + re-render the text to the screen
+ *
+ * Whether to use wrapping or panning can only be figured out at
+ * runtime (when we know whether our font height is a multiple
+ * of the pan/wrap step)
+ *
+ */
+
+#define SCROLL_MOVE	   0x001
+#define SCROLL_PAN_MOVE	   0x002
+#define SCROLL_WRAP_MOVE   0x003
+#define SCROLL_REDRAW	   0x004
+#define SCROLL_PAN_REDRAW  0x005
+
 #ifdef CONFIG_FB_TILEBLITTING
 extern void fbcon_set_tileops(struct vc_data *vc, struct fb_info *info);
 #endif
--- b/drivers/video/fbdev/core/fbcon_ccw.c
+++ a/drivers/video/fbdev/core/fbcon_ccw.c
@@ -59,12 +59,31 @@
 	}
 }
 
+
+static void ccw_bmove(struct vc_data *vc, struct fb_info *info, int sy,
+		     int sx, int dy, int dx, int height, int width)
+{
+	struct fbcon_ops *ops = info->fbcon_par;
+	struct fb_copyarea area;
+	u32 vyres = GETVYRES(ops->p->scrollmode, info);
+
+	area.sx = sy * vc->vc_font.height;
+	area.sy = vyres - ((sx + width) * vc->vc_font.width);
+	area.dx = dy * vc->vc_font.height;
+	area.dy = vyres - ((dx + width) * vc->vc_font.width);
+	area.width = height * vc->vc_font.height;
+	area.height  = width * vc->vc_font.width;
+
+	info->fbops->fb_copyarea(info, &area);
+}
+
 static void ccw_clear(struct vc_data *vc, struct fb_info *info, int sy,
 		     int sx, int height, int width)
 {
+	struct fbcon_ops *ops = info->fbcon_par;
 	struct fb_fillrect region;
 	int bgshift = (vc->vc_hi_font_mask) ? 13 : 12;
+	u32 vyres = GETVYRES(ops->p->scrollmode, info);
-	u32 vyres = info->var.yres;
 
 	region.color = attr_bgcol_ec(bgshift,vc,info);
 	region.dx = sy * vc->vc_font.height;
@@ -121,7 +140,7 @@
 	u32 cnt, pitch, size;
 	u32 attribute = get_attribute(info, scr_readw(s));
 	u8 *dst, *buf = NULL;
+	u32 vyres = GETVYRES(ops->p->scrollmode, info);
-	u32 vyres = info->var.yres;
 
 	if (!ops->fontbuffer)
 		return;
@@ -210,7 +229,7 @@
 	int attribute, use_sw = vc->vc_cursor_type & CUR_SW;
 	int err = 1, dx, dy;
 	char *src;
+	u32 vyres = GETVYRES(ops->p->scrollmode, info);
-	u32 vyres = info->var.yres;
 
 	if (!ops->fontbuffer)
 		return;
@@ -368,7 +387,7 @@
 {
 	struct fbcon_ops *ops = info->fbcon_par;
 	u32 yoffset;
+	u32 vyres = GETVYRES(ops->p->scrollmode, info);
-	u32 vyres = info->var.yres;
 	int err;
 
 	yoffset = (vyres - info->var.yres) - ops->var.xoffset;
@@ -383,6 +402,7 @@
 
 void fbcon_rotate_ccw(struct fbcon_ops *ops)
 {
+	ops->bmove = ccw_bmove;
 	ops->clear = ccw_clear;
 	ops->putcs = ccw_putcs;
 	ops->clear_margins = ccw_clear_margins;
--- b/drivers/video/fbdev/core/fbcon_cw.c
+++ a/drivers/video/fbdev/core/fbcon_cw.c
@@ -44,12 +44,31 @@
 	}
 }
 
+
+static void cw_bmove(struct vc_data *vc, struct fb_info *info, int sy,
+		     int sx, int dy, int dx, int height, int width)
+{
+	struct fbcon_ops *ops = info->fbcon_par;
+	struct fb_copyarea area;
+	u32 vxres = GETVXRES(ops->p->scrollmode, info);
+
+	area.sx = vxres - ((sy + height) * vc->vc_font.height);
+	area.sy = sx * vc->vc_font.width;
+	area.dx = vxres - ((dy + height) * vc->vc_font.height);
+	area.dy = dx * vc->vc_font.width;
+	area.width = height * vc->vc_font.height;
+	area.height  = width * vc->vc_font.width;
+
+	info->fbops->fb_copyarea(info, &area);
+}
+
 static void cw_clear(struct vc_data *vc, struct fb_info *info, int sy,
 		     int sx, int height, int width)
 {
+	struct fbcon_ops *ops = info->fbcon_par;
 	struct fb_fillrect region;
 	int bgshift = (vc->vc_hi_font_mask) ? 13 : 12;
+	u32 vxres = GETVXRES(ops->p->scrollmode, info);
-	u32 vxres = info->var.xres;
 
 	region.color = attr_bgcol_ec(bgshift,vc,info);
 	region.dx = vxres - ((sy + height) * vc->vc_font.height);
@@ -106,7 +125,7 @@
 	u32 cnt, pitch, size;
 	u32 attribute = get_attribute(info, scr_readw(s));
 	u8 *dst, *buf = NULL;
+	u32 vxres = GETVXRES(ops->p->scrollmode, info);
-	u32 vxres = info->var.xres;
 
 	if (!ops->fontbuffer)
 		return;
@@ -193,7 +212,7 @@
 	int attribute, use_sw = vc->vc_cursor_type & CUR_SW;
 	int err = 1, dx, dy;
 	char *src;
+	u32 vxres = GETVXRES(ops->p->scrollmode, info);
-	u32 vxres = info->var.xres;
 
 	if (!ops->fontbuffer)
 		return;
@@ -350,7 +369,7 @@
 static int cw_update_start(struct fb_info *info)
 {
 	struct fbcon_ops *ops = info->fbcon_par;
+	u32 vxres = GETVXRES(ops->p->scrollmode, info);
-	u32 vxres = info->var.xres;
 	u32 xoffset;
 	int err;
 
@@ -366,6 +385,7 @@
 
 void fbcon_rotate_cw(struct fbcon_ops *ops)
 {
+	ops->bmove = cw_bmove;
 	ops->clear = cw_clear;
 	ops->putcs = cw_putcs;
 	ops->clear_margins = cw_clear_margins;
--- b/drivers/video/fbdev/core/fbcon_rotate.h
+++ a/drivers/video/fbdev/core/fbcon_rotate.h
@@ -11,6 +11,15 @@
 #ifndef _FBCON_ROTATE_H
 #define _FBCON_ROTATE_H
 
+#define GETVYRES(s,i) ({                           \
+        (s == SCROLL_REDRAW || s == SCROLL_MOVE) ? \
+        (i)->var.yres : (i)->var.yres_virtual; })
+
+#define GETVXRES(s,i) ({                           \
+        (s == SCROLL_REDRAW || s == SCROLL_MOVE || !(i)->fix.xpanstep) ? \
+        (i)->var.xres : (i)->var.xres_virtual; })
+
+
 static inline int pattern_test_bit(u32 x, u32 y, u32 pitch, const char *pat)
 {
 	u32 tmp = (y * pitch) + x, index = tmp / 8,  bit = tmp % 8;
--- b/drivers/video/fbdev/core/fbcon_ud.c
+++ a/drivers/video/fbdev/core/fbcon_ud.c
@@ -44,13 +44,33 @@
 	}
 }
 
+
+static void ud_bmove(struct vc_data *vc, struct fb_info *info, int sy,
+		     int sx, int dy, int dx, int height, int width)
+{
+	struct fbcon_ops *ops = info->fbcon_par;
+	struct fb_copyarea area;
+	u32 vyres = GETVYRES(ops->p->scrollmode, info);
+	u32 vxres = GETVXRES(ops->p->scrollmode, info);
+
+	area.sy = vyres - ((sy + height) * vc->vc_font.height);
+	area.sx = vxres - ((sx + width) * vc->vc_font.width);
+	area.dy = vyres - ((dy + height) * vc->vc_font.height);
+	area.dx = vxres - ((dx + width) * vc->vc_font.width);
+	area.height = height * vc->vc_font.height;
+	area.width  = width * vc->vc_font.width;
+
+	info->fbops->fb_copyarea(info, &area);
+}
+
 static void ud_clear(struct vc_data *vc, struct fb_info *info, int sy,
 		     int sx, int height, int width)
 {
+	struct fbcon_ops *ops = info->fbcon_par;
 	struct fb_fillrect region;
 	int bgshift = (vc->vc_hi_font_mask) ? 13 : 12;
+	u32 vyres = GETVYRES(ops->p->scrollmode, info);
+	u32 vxres = GETVXRES(ops->p->scrollmode, info);
-	u32 vyres = info->var.yres;
-	u32 vxres = info->var.xres;
 
 	region.color = attr_bgcol_ec(bgshift,vc,info);
 	region.dy = vyres - ((sy + height) * vc->vc_font.height);
@@ -142,8 +162,8 @@
 	u32 mod = vc->vc_font.width % 8, cnt, pitch, size;
 	u32 attribute = get_attribute(info, scr_readw(s));
 	u8 *dst, *buf = NULL;
+	u32 vyres = GETVYRES(ops->p->scrollmode, info);
+	u32 vxres = GETVXRES(ops->p->scrollmode, info);
-	u32 vyres = info->var.yres;
-	u32 vxres = info->var.xres;
 
 	if (!ops->fontbuffer)
 		return;
@@ -239,8 +259,8 @@
 	int attribute, use_sw = vc->vc_cursor_type & CUR_SW;
 	int err = 1, dx, dy;
 	char *src;
+	u32 vyres = GETVYRES(ops->p->scrollmode, info);
+	u32 vxres = GETVXRES(ops->p->scrollmode, info);
-	u32 vyres = info->var.yres;
-	u32 vxres = info->var.xres;
 
 	if (!ops->fontbuffer)
 		return;
@@ -390,8 +410,8 @@
 {
 	struct fbcon_ops *ops = info->fbcon_par;
 	int xoffset, yoffset;
+	u32 vyres = GETVYRES(ops->p->scrollmode, info);
+	u32 vxres = GETVXRES(ops->p->scrollmode, info);
-	u32 vyres = info->var.yres;
-	u32 vxres = info->var.xres;
 	int err;
 
 	xoffset = vxres - info->var.xres - ops->var.xoffset;
@@ -409,6 +429,7 @@
 
 void fbcon_rotate_ud(struct fbcon_ops *ops)
 {
+	ops->bmove = ud_bmove;
 	ops->clear = ud_clear;
 	ops->putcs = ud_putcs;
 	ops->clear_margins = ud_clear_margins;
--- b/drivers/video/fbdev/core/tileblit.c
+++ a/drivers/video/fbdev/core/tileblit.c
@@ -16,6 +16,21 @@
 #include <asm/types.h>
 #include "fbcon.h"
 
+static void tile_bmove(struct vc_data *vc, struct fb_info *info, int sy,
+		       int sx, int dy, int dx, int height, int width)
+{
+	struct fb_tilearea area;
+
+	area.sx = sx;
+	area.sy = sy;
+	area.dx = dx;
+	area.dy = dy;
+	area.height = height;
+	area.width = width;
+
+	info->tileops->fb_tilecopy(info, &area);
+}
+
 static void tile_clear(struct vc_data *vc, struct fb_info *info, int sy,
 		       int sx, int height, int width)
 {
@@ -118,6 +133,7 @@
 	struct fb_tilemap map;
 	struct fbcon_ops *ops = info->fbcon_par;
 
+	ops->bmove = tile_bmove;
 	ops->clear = tile_clear;
 	ops->putcs = tile_putcs;
 	ops->clear_margins = tile_clear_margins;
--- b/drivers/video/fbdev/skeletonfb.c
+++ a/drivers/video/fbdev/skeletonfb.c
@@ -505,15 +505,15 @@
 }
 
 /**
+ *      xxxfb_copyarea - REQUIRED function. Can use generic routines if
+ *                       non acclerated hardware and packed pixel based.
- *      xxxfb_copyarea - OBSOLETE function.
  *                       Copies one area of the screen to another area.
- *                       Will be deleted in a future version
  *
  *      @info: frame buffer structure that represents a single frame buffer
  *      @area: Structure providing the data to copy the framebuffer contents
  *	       from one region to another.
  *
+ *      This drawing operation copies a rectangular area from one area of the
- *      This drawing operation copied a rectangular area from one area of the
  *	screen to another area.
  */
 void xxxfb_copyarea(struct fb_info *p, const struct fb_copyarea *area) 
@@ -645,9 +645,9 @@
 	.fb_setcolreg	= xxxfb_setcolreg,
 	.fb_blank	= xxxfb_blank,
 	.fb_pan_display	= xxxfb_pan_display,
+	.fb_fillrect	= xxxfb_fillrect, 	/* Needed !!! */
+	.fb_copyarea	= xxxfb_copyarea,	/* Needed !!! */
+	.fb_imageblit	= xxxfb_imageblit,	/* Needed !!! */
-	.fb_fillrect	= xxxfb_fillrect,	/* Needed !!!   */
-	.fb_copyarea	= xxxfb_copyarea,	/* Obsolete     */
-	.fb_imageblit	= xxxfb_imageblit,	/* Needed !!!   */
 	.fb_cursor	= xxxfb_cursor,		/* Optional !!! */
 	.fb_sync	= xxxfb_sync,
 	.fb_ioctl	= xxxfb_ioctl,
--- b/include/linux/fb.h
+++ a/include/linux/fb.h
@@ -262,7 +262,7 @@
 
 	/* Draws a rectangle */
 	void (*fb_fillrect) (struct fb_info *info, const struct fb_fillrect *rect);
+	/* Copy data from area to another */
-	/* Copy data from area to another. Obsolete. */
 	void (*fb_copyarea) (struct fb_info *info, const struct fb_copyarea *region);
 	/* Draws a image to the display */
 	void (*fb_imageblit) (struct fb_info *info, const struct fb_image *image);