The calculated ideal rate can easily overflow an unsigned long, thus
making the best div selection buggy as soon as no ideal match is found
before the overflow occurs.
Fixes: 4731a72df273 ("drm/sun4i: request exact rates to our parents")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181018100250.12565-1-boris.brezillon@bootlin.com
int i;
for (i = tcon->dclk_min_div; i <= tcon->dclk_max_div; i++) {
- unsigned long ideal = rate * i;
+ u64 ideal = (u64)rate * i;
unsigned long rounded;
+ /*
+ * ideal has overflowed the max value that can be stored in an
+ * unsigned long, and every clk operation we might do on a
+ * truncated u64 value will give us incorrect results.
+ * Let's just stop there since bigger dividers will result in
+ * the same overflow issue.
+ */
+ if (ideal > ULONG_MAX)
+ goto out;
+
rounded = clk_hw_round_rate(clk_hw_get_parent(hw),
ideal);