clk: add pr_debug & kerneldoc around clk notifiers

Both the pr_err and the additional kerneldoc aim to help when debugging
errors thrown from within a clock rate-change notifier callback.

Reported-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Acked-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index a6f079d23eaa2bd7af71a62ec62049576b7a1712..f30e6af90332b53b903688d04cbad7af1db15c9b 100644 (file)
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1339,8 +1339,11 @@ static int __clk_speculate_rates(struct clk *clk, unsigned long parent_rate)
        if (clk->notifier_count)
                ret = __clk_notify(clk, PRE_RATE_CHANGE, clk->rate, new_rate);
 
-       if (ret & NOTIFY_STOP_MASK)
+       if (ret & NOTIFY_STOP_MASK) {
+               pr_debug("%s: clk notifier callback for clock %s aborted with error %d\n",
+                               __func__, clk->name, ret);
                goto out;
+       }
 
        hlist_for_each_entry(child, &clk->children, child_node) {
                ret = __clk_speculate_rates(child, new_rate);

diff --git a/include/linux/clk.h b/include/linux/clk.h
index 0dd91148165e4e7df78beb5582b89910c1615f26..fb5e097d8f72b07fb34e480bb817593284dccdd2 100644 (file)
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -78,8 +78,22 @@ struct clk_notifier_data {
        unsigned long           new_rate;
 };
 
+/**
+ * clk_notifier_register: register a clock rate-change notifier callback
+ * @clk: clock whose rate we are interested in
+ * @nb: notifier block with callback function pointer
+ *
+ * ProTip: debugging across notifier chains can be frustrating. Make sure that
+ * your notifier callback function prints a nice big warning in case of
+ * failure.
+ */
 int clk_notifier_register(struct clk *clk, struct notifier_block *nb);
 
+/**
+ * clk_notifier_unregister: unregister a clock rate-change notifier callback
+ * @clk: clock whose rate we are no longer interested in
+ * @nb: notifier block which will be unregistered
+ */
 int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb);
 
 /**