Revert "fbcon: Disable accelerated scrolling"
[linux-2.6-microblaze.git] / drivers / video / fbdev / core / fbcon.c
index 99ecd9a..0cc2a36 100644 (file)
@@ -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;