rtc: NTP: Add CONFIG_RTC_SYSTOHC_DEVICE for NTP synchronization

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

Cc: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index c94bb6a..efaff36 100644 (file)
--- 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
        default "rtc0"
        help
          The RTC device that will be used to (re)initialize the system
@@ -56,6 +48,25 @@ 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
+       default RTC_HCTOSYS_DEVICE if RTC_HCTOSYS
+       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 (file)
--- 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. */