rtc: initialize emulated RTC from environment variable
Up to now the emulated RTC is initialized using the U-Boot build time.
With this patch the environment variable 'rtc_emul_epoch' can be used to
provide a better initial time. The variable is a decimal string with
the number of seconds since 1970-01-01. Here is an example where the RTC
had not been probed yet:
=> setenv rtc_emul_epoch 1610109000
=> date
Date: 2021-01-08 (Friday) Time: 12:30:00
If the variable does not exist, the U-Boot build time is used as fallback.
The environment variable may be set when shutting down the operating system
if the U-Boot environment is exposed to the OS (cf. ENV_IS_IN_FAT and
ENV_IS_IN_EXT4).
Suggested-by: Pablo Sebastián Greco <pgreco@centosproject.org>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index d06d272..cad667a 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -68,11 +68,14 @@
depends on DM_RTC
help
On a board without hardware clock this software real time clock can be
- used. The build time is used to initialize the RTC. So you will have
- to adjust the time either manually using the 'date' command or use
- the 'sntp' to update the RTC with the time from a network time server.
- See CONFIG_CMD_SNTP and CONFIG_BOOTP_NTPSERVER. The RTC time is
- advanced according to CPU ticks.
+ used. The initial time may be provided via the environment variable
+ 'rtc_emul_epoch' as a decimal string indicating seconds since
+ 1970-01-01. If the environment variable is missing, the build time is
+ used to initialize the RTC. The time can be adjusted manually via the
+ 'date' command or the 'sntp' command can be used to update the RTC
+ with the time from a network time server. See CONFIG_CMD_SNTP and
+ CONFIG_BOOTP_NTPSERVER. The RTC time is advanced according to CPU
+ ticks.
config RTC_ISL1208
bool "Enable ISL1208 driver"