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Subject[PATCH v2 1/4] NTP: rtc: Add CONFIG_RTC_SYSTOHC_DEVICE for NTP synchronization
Date
From: Xunlei Pang <pang.xunlei@linaro.org>

Currently, CONFIG_RTC_SYSTOHC uses CONFIG_RTC_HCTOSYS_DEVICE which
is originally used by CONFIG_RTC_HCTOSYS, but this rtc device has
some limiations, for example, it must be battery-backed, be able
to work with irq off and through system suspension, etc.

So add CONFIG_RTC_SYSTOHC_DEVICE used exclusively for CONFIG_RTC_SYSTOHC,
it is more lenient compared to CONFIG_RTC_HCTOSYS_DEVICE, and could
be assigned any available RTC in the system. Default value is "rtc0".

After this patch, NTP will sync up "rtc0" by default.

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
---
drivers/rtc/Kconfig | 28 +++++++++++++++++++---------
drivers/rtc/systohc.c | 2 +-
2 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 0fe4ad8..f429e9a 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -25,17 +25,9 @@ config RTC_HCTOSYS
the value read from a specified RTC device. This is useful to avoid
unnecessary fsck runs at boot time, and to network better.

-config RTC_SYSTOHC
- bool "Set the RTC time based on NTP synchronization"
- default y
- help
- If you say yes here, the system time (wall clock) will be stored
- in the RTC specified by RTC_HCTOSYS_DEVICE approximately every 11
- minutes if userspace reports synchronized NTP status.
-
config RTC_HCTOSYS_DEVICE
string "RTC used to set the system time"
- depends on RTC_HCTOSYS = y || RTC_SYSTOHC = y
+ depends on RTC_HCTOSYS = y
default "rtc0"
help
The RTC device that will be used to (re)initialize the system
@@ -56,6 +48,24 @@ config RTC_HCTOSYS_DEVICE
sleep states. Do not specify an RTC here unless it stays powered
during all this system's supported sleep states.

+config RTC_SYSTOHC
+ bool "Set the RTC time based on NTP synchronization"
+ default y
+ help
+ If you say yes here, the system time (wall clock) will be stored
+ in the RTC specified by RTC_HCTOSYS_DEVICE approximately every 11
+ minutes if userspace reports synchronized NTP status.
+
+config RTC_SYSTOHC_DEVICE
+ string "RTC used to synchronize NTP adjustment"
+ depends on RTC_SYSTOHC = y
+ default "rtc0"
+ help
+ The RTC device used for NTP synchronization. The main difference
+ between RTC_HCTOSYS_DEVICE and RTC_SYSTOHC_DEVICE is that this
+ one can sleep when setting time, because it runs in the workqueue
+ context.
+
config RTC_DEBUG
bool "RTC debug support"
help
diff --git a/drivers/rtc/systohc.c b/drivers/rtc/systohc.c
index 7728d5e..b4a68ff 100644
--- a/drivers/rtc/systohc.c
+++ b/drivers/rtc/systohc.c
@@ -31,7 +31,7 @@ int rtc_set_ntp_time(struct timespec64 now)
else
rtc_time64_to_tm(now.tv_sec + 1, &tm);

- rtc = rtc_class_open(CONFIG_RTC_HCTOSYS_DEVICE);
+ rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
if (rtc) {
/* rtc_hctosys exclusively uses UTC, so we call set_time here,
* not set_mmss. */
--
1.9.1



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