ARM: shmobile: r8a73a4: safeguard against wrong clk_set_rate() uses

clk_set_rate() should only be called with exact rates, returned by
clk_round_rate(). However, it is still good to verify, that the value,
passed to clock's .set_rate() method is at least valid. This patch adds
such a check for the Z-clock on r8a73a4.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

1 files changed, 13 insertions, 1 deletions

diff --git a/arch/arm/mach-shmobile/clock-r8a73a4.c b/arch/arm/mach-shmobile/clock-r8a73a4.c
index 824789c26fb6..22f10ff40272 100644
--- a/arch/arm/mach-shmobile/clock-r8a73a4.c
+++ b/arch/arm/mach-shmobile/clock-r8a73a4.c
@@ -225,16 +225,28 @@ static int zclk_set_rate(struct clk *clk, unsigned long rate)
                 goto done;
         }
 
-        frqcrc = clk->mapped_reg + (FRQCRC - (u32)clk->enable_reg);
+        /*
+         * Users are supposed to first call clk_set_rate() only with
+         * clk_round_rate() results. So, we don't fix wrong rates here, but
+         * guard against them anyway
+         */
 
         p_rate = clk_get_rate(clk->parent);
         if (rate == p_rate) {
                 val = 0;
         } else {
                 step = DIV_ROUND_CLOSEST(p_rate, 32);
+
+                if (rate > p_rate || rate < step) {
+                        ret = -EINVAL;
+                        goto done;
+                }
+
                 val = 32 - rate / step;
         }
 
+        frqcrc = clk->mapped_reg + (FRQCRC - (u32)clk->enable_reg);
+
         iowrite32((ioread32(frqcrc) & ~(clk->div_mask << clk->enable_bit)) |
                   (val << clk->enable_bit), frqcrc);