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authorStephen Warren <swarren@nvidia.com>2014-01-23 15:55:14 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-23 16:37:00 -0800
commit9d2b7e532da8aadfcc1bd85b62ec5dd853e870e3 (patch)
tree093b6f145151ab967989b9552a8e349396d00168 /drivers
parent7ab26cd1ef817bca74cf82116eaf9eb5fe4a56c7 (diff)
rtc: honor device tree /alias entries when assigning IDs
Assign RTC device IDs based on device tree /aliases entries if present, falling back to the existing numbering scheme if there is no /aliases entry (which includes when the system isn't booted using DT), or there is a numbering conflict. This is useful in systems with multiple RTC devices, to ensure that the best RTC device is selected as /dev/rtc0, which provides the overall system time. For example, Tegra has an on-SoC RTC that is not battery backed, typically coupled with an off-SoC RTC that is battery backed. Only the latter is useful for populating the system time, yet the former is useful e.g. for wakeup timing, since the time is not lost when the system is sleeps. Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/rtc/class.c24
1 files changed, 20 insertions, 4 deletions
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 02426812bebc..589351ef75d0 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -14,6 +14,7 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
+#include <linux/of.h>
#include <linux/rtc.h>
#include <linux/kdev_t.h>
#include <linux/idr.h>
@@ -157,12 +158,27 @@ struct rtc_device *rtc_device_register(const char *name, struct device *dev,
{
struct rtc_device *rtc;
struct rtc_wkalrm alrm;
- int id, err;
+ int of_id = -1, id = -1, err;
+
+ if (dev->of_node)
+ of_id = of_alias_get_id(dev->of_node, "rtc");
+ else if (dev->parent && dev->parent->of_node)
+ of_id = of_alias_get_id(dev->parent->of_node, "rtc");
+
+ if (of_id >= 0) {
+ id = ida_simple_get(&rtc_ida, of_id, of_id + 1,
+ GFP_KERNEL);
+ if (id < 0)
+ dev_warn(dev, "/aliases ID %d not available\n",
+ of_id);
+ }
- id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
if (id < 0) {
- err = id;
- goto exit;
+ id = ida_simple_get(&rtc_ida, 0, 0, GFP_KERNEL);
+ if (id < 0) {
+ err = id;
+ goto exit;
+ }
}
rtc = kzalloc(sizeof(struct rtc_device), GFP_KERNEL);

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