auxdisplay: charlcd: Add support for displays with more than two lines

On displays with more than two lines, the additional lines are stored in
the buffers used for the first two lines, but beyond the visible parts.
Adjust the DDRAM address calculation to cater for this.

When clearing the display, avoid writing more spaces than the actual
size of the physical buffer.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/auxdisplay/charlcd.c

@@ -159,15 +159,19 @@ EXPORT_SYMBOL_GPL(charlcd_poke);
 static void charlcd_gotoxy(struct charlcd *lcd)
 {
 	struct charlcd_priv *priv = to_priv(lcd);
+	unsigned int addr;
 
-	lcd->ops->write_cmd(lcd,
-		LCD_CMD_SET_DDRAM_ADDR | (priv->addr.y ? lcd->hwidth : 0) |
 	/*
 	 * we force the cursor to stay at the end of the
 	 * line if it wants to go farther
 	 */
-		((priv->addr.x < lcd->bwidth) ? priv->addr.x & (lcd->hwidth - 1)
-					      : lcd->bwidth - 1));
+	addr = priv->addr.x < lcd->bwidth ? priv->addr.x & (lcd->hwidth - 1)
+					  : lcd->bwidth - 1;
+	if (priv->addr.y & 1)
+		addr += lcd->hwidth;
+	if (priv->addr.y & 2)
+		addr += lcd->bwidth;
+	lcd->ops->write_cmd(lcd, LCD_CMD_SET_DDRAM_ADDR | addr);
 }
 
 static void charlcd_home(struct charlcd *lcd)
@@ -203,7 +207,7 @@ static void charlcd_clear_fast(struct charlcd *lcd)
 	if (lcd->ops->clear_fast)
 		lcd->ops->clear_fast(lcd);
 	else
-		for (pos = 0; pos < lcd->height * lcd->hwidth; pos++)
+		for (pos = 0; pos < min(2, lcd->height) * lcd->hwidth; pos++)
 			lcd->ops->write_data(lcd, ' ');
 
 	charlcd_home(lcd);