X-Git-Url: http://git.monstr.eu/?a=blobdiff_plain;f=drivers%2Fvideo%2Ffbdev%2Fcore%2Ffbcon.c;h=0cc2a36b674a374632f214bc99a8371f19b365f3;hb=87ab9f6b7417349aa197a6c7098d4fdd4beebb74;hp=99ecd9a6d844ad9bfd68cfc0ffc8f73398ab558a;hpb=7413927713388c21d844b38444fb2b91e077ab2f;p=linux-2.6-microblaze.git

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 99ecd9a6d844..0cc2a36b674a 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -173,6 +173,8 @@ static void fbcon_putcs(struct vc_data *vc, const unsigned short *s,
 			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 @@ static void fbcon_set_palette(struct vc_data *vc, const unsigned char *table);
 /*
  *  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);
@@ -1015,7 +1025,7 @@ static void fbcon_init(struct vc_data *vc, int init)
 	struct vc_data *svc = *default_mode;
 	struct fbcon_display *t, *p = &fb_display[vc->vc_num];
 	int logo = 1, new_rows, new_cols, rows, cols;
-	int ret;
+	int cap, ret;
 
 	if (WARN_ON(info_idx == -1))
 	    return;
@@ -1024,6 +1034,7 @@ static void fbcon_init(struct vc_data *vc, int init)
 		con2fb_map[vc->vc_num] = info_idx;
 
 	info = registered_fb[con2fb_map[vc->vc_num]];
+	cap = info->flags;
 
 	if (logo_shown < 0 && console_loglevel <= CONSOLE_LOGLEVEL_QUIET)
 		logo_shown = FBCON_LOGO_DONTSHOW;
@@ -1125,6 +1136,12 @@ static void fbcon_init(struct vc_data *vc, int init)
 
 	ops->graphics = 0;
 
+	if ((cap & FBINFO_HWACCEL_COPYAREA) &&
+	    !(cap & FBINFO_HWACCEL_DISABLED))
+		p->scrollmode = SCROLL_MOVE;
+	else /* default to something safe */
+		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 +1228,14 @@ finished:
  *  This system is now divided into two levels because of complications
  *  caused by hardware scrolling. Top level functions:
  *
- *	fbcon_clear(), fbcon_putc(), fbcon_clear_margins()
+ *	fbcon_bmove(), 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 +1408,224 @@ static void fbcon_set_disp(struct fb_info *info, struct fb_var_screeninfo *var,
 	}
 }
 
+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 +1686,7 @@ static bool fbcon_scroll(struct vc_data *vc, unsigned int t, unsigned int b,
 {
 	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;
@@ -1466,47 +1703,294 @@ static bool fbcon_scroll(struct vc_data *vc, unsigned int t, unsigned int b,
 	case SM_UP:
 		if (count > vc->vc_rows)	/* Maximum realistic size */
 			count = vc->vc_rows;
-		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;
+		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;
 
 	case SM_DOWN:
 		if (count > vc->vc_rows)	/* Maximum realistic size */
 			count = vc->vc_rows;
-		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;
+		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;
+		}
 	}
 	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)
 {
 	struct fbcon_ops *ops = info->fbcon_par;
 	int fh = vc->vc_font.height;
+	int cap = info->flags;
+	u16 t = 0;
+	int ypan = FBCON_SWAP(ops->rotate, info->fix.ypanstep,
+				  info->fix.xpanstep);
+	int ywrap = FBCON_SWAP(ops->rotate, info->fix.ywrapstep, t);
 	int yres = FBCON_SWAP(ops->rotate, info->var.yres, info->var.xres);
 	int vyres = FBCON_SWAP(ops->rotate, info->var.yres_virtual,
 				   info->var.xres_virtual);
+	int good_pan = (cap & FBINFO_HWACCEL_YPAN) &&
+		divides(ypan, vc->vc_font.height) && vyres > yres;
+	int good_wrap = (cap & FBINFO_HWACCEL_YWRAP) &&
+		divides(ywrap, vc->vc_font.height) &&
+		divides(vc->vc_font.height, vyres) &&
+		divides(vc->vc_font.height, yres);
+	int reading_fast = cap & FBINFO_READS_FAST;
+	int fast_copyarea = (cap & FBINFO_HWACCEL_COPYAREA) &&
+		!(cap & FBINFO_HWACCEL_DISABLED);
+	int fast_imageblit = (cap & FBINFO_HWACCEL_IMAGEBLIT) &&
+		!(cap & FBINFO_HWACCEL_DISABLED);
 
 	p->vrows = vyres/fh;
 	if (yres > (fh * (vc->vc_rows + 1)))
 		p->vrows -= (yres - (fh * vc->vc_rows)) / fh;
 	if ((yres % fh) && (vyres % fh < yres % fh))
 		p->vrows--;
+
+	if (good_wrap || good_pan) {
+		if (reading_fast || fast_copyarea)
+			p->scrollmode = good_wrap ?
+				SCROLL_WRAP_MOVE : SCROLL_PAN_MOVE;
+		else
+			p->scrollmode = good_wrap ? SCROLL_REDRAW :
+				SCROLL_PAN_REDRAW;
+	} else {
+		if (reading_fast || (fast_copyarea && !fast_imageblit))
+			p->scrollmode = SCROLL_MOVE;
+		else
+			p->scrollmode = SCROLL_REDRAW;
+	}
 }
 
 #define PITCH(w) (((w) + 7) >> 3)
@@ -1664,7 +2148,21 @@ static int fbcon_switch(struct vc_data *vc)
 
 	updatescrollmode(p, info, vc);
 
-	scrollback_phys_max = 0;
+	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_max = 0;
 	scrollback_current = 0;