rtc: ac100: Fix ac100 determine rate bug

[sfrench/cifs-2.6.git] / drivers / rtc / rtc-ac100.c

diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c
index 080e3c04be43bd98bc02af33716a77cfaa676c63..3fe576fdd45e0782a1ecead2931ddf95d76d8a8d 100644 (file)
--- a/drivers/rtc/rtc-ac100.c
+++ b/drivers/rtc/rtc-ac100.c
@@ -183,7 +183,29 @@ static int ac100_clkout_determine_rate(struct clk_hw *hw,
 
        for (i = 0; i < num_parents; i++) {
                struct clk_hw *parent = clk_hw_get_parent_by_index(hw, i);
-               unsigned long tmp, prate = clk_hw_get_rate(parent);
+               unsigned long tmp, prate;
+
+               /*
+                * The clock has two parents, one is a fixed clock which is
+                * internally registered by the ac100 driver. The other parent
+                * is a clock from the codec side of the chip, which we
+                * properly declare and reference in the devicetree and is
+                * not implemented in any driver right now.
+                * If the clock core looks for the parent of that second
+                * missing clock, it can't find one that is registered and
+                * returns NULL.
+                * So we end up in a situation where clk_hw_get_num_parents
+                * returns the amount of clocks we can be parented to, but
+                * clk_hw_get_parent_by_index will not return the orphan
+                * clocks.
+                * Thus we need to check if the parent exists before
+                * we get the parent rate, so we could use the RTC
+                * without waiting for the codec to be supported.
+                */
+               if (!parent)
+                       continue;
+
+               prate = clk_hw_get_rate(parent);
 
                tmp = ac100_clkout_round_rate(hw, req->rate, prate);