sm501fb: fix timing limits

Vertical sync height register can only hold 6 bits.  Fix the hsync start test
to use > instead of >=.  Also add a few clarifying comments.

Signed-off-by: Ville Syrjala <syrjala@sci.fi>
Acked-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/video/sm501fb.c b/drivers/video/sm501fb.c
index f49287c88abe..742b5c656d66 100644
--- a/drivers/video/sm501fb.c
+++ b/drivers/video/sm501fb.c
@@ -237,12 +237,14 @@ static int sm501fb_check_var(struct fb_var_screeninfo *var,
 
         /* check we can fit these values into the registers */
 
-        if (var->hsync_len > 255 || var->vsync_len > 255)
+        if (var->hsync_len > 255 || var->vsync_len > 63)
                 return -EINVAL;
 
-        if ((var->xres + var->right_margin) >= 4096)
+        /* hdisplay end and hsync start */
+        if ((var->xres + var->right_margin) > 4096)
                 return -EINVAL;
 
+        /* vdisplay end and vsync start */
         if ((var->yres + var->lower_margin) > 2048)
                 return -EINVAL;