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"
diff --git a/drivers/rtc/emul_rtc.c b/drivers/rtc/emul_rtc.c
index 209b496..7e52210 100644
--- a/drivers/rtc/emul_rtc.c
+++ b/drivers/rtc/emul_rtc.c
@@ -8,6 +8,7 @@
#include <common.h>
#include <div64.h>
#include <dm.h>
+#include <env.h>
#include <generated/timestamp_autogenerated.h>
#include <rtc.h>
@@ -60,9 +61,18 @@
int emul_rtc_probe(struct udevice *dev)
{
struct emul_rtc *priv = dev_get_priv(dev);
+ const char *epoch_str;
+ u64 epoch;
+
+ epoch_str = env_get("rtc_emul_epoch");
- /* Use the build date as initial time */
- priv->offset_us = U_BOOT_EPOCH * 1000000ULL - timer_get_us();
+ if (epoch_str) {
+ epoch = simple_strtoull(epoch_str, NULL, 10);
+ } else {
+ /* Use the build date as initial time */
+ epoch = U_BOOT_EPOCH;
+ }
+ priv->offset_us = epoch * 1000000ULL - timer_get_us();
priv->isdst = -1;
return 0;