atmel_lcdfb: validate display timings

Setting a display timing parameter too high or too low may cause it to
wrap around and thus become completely wrong. Validate the timings in
atmel_lcdfb_check_var() and saturate to the highest or lowest possible
value if necessary.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/video/atmel_lcdfb.c

@@ -203,6 +203,26 @@ static int atmel_lcdfb_check_var(struct fb_var_screeninfo *var,
 	var->transp.offset = var->transp.length = 0;
 	var->xoffset = var->yoffset = 0;
 
+	/* Saturate vertical and horizontal timings at maximum values */
+	var->vsync_len = min_t(u32, var->vsync_len,
+			(ATMEL_LCDC_VPW >> ATMEL_LCDC_VPW_OFFSET) + 1);
+	var->upper_margin = min_t(u32, var->upper_margin,
+			ATMEL_LCDC_VBP >> ATMEL_LCDC_VBP_OFFSET);
+	var->lower_margin = min_t(u32, var->lower_margin,
+			ATMEL_LCDC_VFP);
+	var->right_margin = min_t(u32, var->right_margin,
+			(ATMEL_LCDC_HFP >> ATMEL_LCDC_HFP_OFFSET) + 1);
+	var->hsync_len = min_t(u32, var->hsync_len,
+			(ATMEL_LCDC_HPW >> ATMEL_LCDC_HPW_OFFSET) + 1);
+	var->left_margin = min_t(u32, var->left_margin,
+			ATMEL_LCDC_HBP + 1);
+
+	/* Some parameters can't be zero */
+	var->vsync_len = max_t(u32, var->vsync_len, 1);
+	var->right_margin = max_t(u32, var->right_margin, 1);
+	var->hsync_len = max_t(u32, var->hsync_len, 1);
+	var->left_margin = max_t(u32, var->left_margin, 1);
+
 	switch (var->bits_per_pixel) {
 	case 1:
 	case 2: