[PATCH 1/2] clockevents: introduce ->set_dev_mode() which can return error

[Kevin Hilman]

From: Viresh Kumar <viresh.kumar at linaro.org>

Currently, the ->set_mode() method of a clockevent device is not
allowed to fail, so it has no return value.  In order to add new
clockevent modes, and allow the setting of those modes to fail, we
need the clockevent core to be able to detect when setting a mode
fails.

To allow detection of mode setting failures, introduce a new method
->set_dev_mode() which can return an error if the given mode is not
supported or fails.

Since all current modes are still not allowed to fail, the core code
simply WARNs if any modes fail.  Future patches that add new mode
support will add proper error recovery based on failure conditions.

Signed-off-by: Viresh Kumar <viresh.kumar at linaro.org>
Reviewed-by: Kevin Hilman <khilman at linaro.org>
[khilman: rework changelogs, minor formatting/checkpatch cleanups]
Signed-off-by: Kevin Hilman <khilman at linaro.org>
---
 include/linux/clockchips.h |  5 ++++-
 kernel/time/clockevents.c  | 21 ++++++++++++++++++---
 kernel/time/timer_list.c   |  5 ++++-
 3 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
index 2e4cb67f6e56..d969659cf688 100644
--- a/include/linux/clockchips.h
+++ b/include/linux/clockchips.h
@@ -81,7 +81,8 @@ enum clock_event_mode {
  * @mode:		operating mode assigned by the management code
  * @features:		features
  * @retries:		number of forced programming retries
- * @set_mode:		set mode function
+ * @set_dev_mode:	set dev mode function
+ * @set_mode:		set mode function (deprecated, use set_dev_mode instead)
  * @broadcast:		function to broadcast events
  * @min_delta_ticks:	minimum delta value in ticks stored for reconfiguration
  * @max_delta_ticks:	maximum delta value in ticks stored for reconfiguration
@@ -109,6 +110,8 @@ struct clock_event_device {
 	unsigned long		retries;
 
 	void			(*broadcast)(const struct cpumask *mask);
+	int			(*set_dev_mode)(enum clock_event_mode mode,
+						struct clock_event_device *);
 	void			(*set_mode)(enum clock_event_mode mode,
 					    struct clock_event_device *);
 	void			(*suspend)(struct clock_event_device *);
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 55449909f114..f7614041240e 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -105,7 +105,16 @@ void clockevents_set_mode(struct clock_event_device *dev,
 				 enum clock_event_mode mode)
 {
 	if (dev->mode != mode) {
-		dev->set_mode(mode, dev);
+		if (dev->set_dev_mode) {
+			int ret = dev->set_dev_mode(mode, dev);
+
+			/* Currently available modes shouldn't fail */
+			WARN_ONCE(ret, "Requested mode: %d, error: %d\n",
+				  mode, ret);
+		} else {
+			dev->set_mode(mode, dev);
+		}
+
 		dev->mode = mode;
 
 		/*
@@ -448,8 +457,14 @@ int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
 	if (dev->mode == CLOCK_EVT_MODE_ONESHOT)
 		return clockevents_program_event(dev, dev->next_event, false);
 
-	if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
-		dev->set_mode(CLOCK_EVT_MODE_PERIODIC, dev);
+	if (dev->mode == CLOCK_EVT_MODE_PERIODIC) {
+		/* Shouldn't fail while switching to PERIODIC MODE */
+		if (dev->set_dev_mode)
+			WARN_ON_ONCE(dev->set_dev_mode(CLOCK_EVT_MODE_PERIODIC,
+						       dev));
+		else
+			dev->set_mode(CLOCK_EVT_MODE_PERIODIC, dev);
+	}
 
 	return 0;
 }
diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index 61ed862cdd37..957a04951ef0 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -229,7 +229,10 @@ print_tickdevice(struct seq_file *m, struct tick_device *td, int cpu)
 	SEQ_printf(m, "\n");
 
 	SEQ_printf(m, " set_mode:       ");
-	print_name_offset(m, dev->set_mode);
+	if (dev->set_dev_mode)
+		print_name_offset(m, dev->set_dev_mode);
+	else
+		print_name_offset(m, dev->set_mode);
 	SEQ_printf(m, "\n");
 
 	SEQ_printf(m, " event_handler:  ");
-- 
2.1.3