[PATCH 1/1] rtc: provide an emulated RTC

[Heinrich Schuchardt]

For testing purposes like running the UEFI SCT an RTC may be required.
Provide an emulated RTC if we do not have a hardware one.

Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
---
 MAINTAINERS            |  1 +
 drivers/rtc/Kconfig    |  6 ++++
 drivers/rtc/Makefile   |  1 +
 drivers/rtc/emul_rtc.c | 79 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 87 insertions(+)
 create mode 100644 drivers/rtc/emul_rtc.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 196d635bdd..2465b51136 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -675,6 +675,7 @@ S:	Maintained
 T:	git https://gitlab.denx.de/u-boot/custodians/u-boot-efi.git
 F:	doc/api/efi.rst
 F:	doc/uefi/*
+F:	drivers/rtc/emul_rtc.c
 F:	include/capitalization.h
 F:	include/charset.h
 F:	include/cp1250.h
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 59e2fc44ba..5c22d70ca9 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -63,6 +63,12 @@ config RTC_DS3232
 	  Support for Dallas Semiconductor (now Maxim) DS3232 compatible
 	  Real Time Clock devices.

+config RTC_EMULATION
+	bool "Enable emulated RTC"
+	depends on DM_RTC
+	help
+	  Provide an emulated real time clock for testing purposes.
+
 config RTC_ISL1208
 	bool "Enable ISL1208 driver"
 	depends on DM_RTC
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 12eb449583..ef66dc4bf0 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_RTC_DS164x) += ds164x.o
 obj-$(CONFIG_RTC_DS174x) += ds174x.o
 obj-$(CONFIG_RTC_DS3231) += ds3231.o
 obj-$(CONFIG_RTC_DS3232) += ds3232.o
+obj-$(CONFIG_RTC_EMULATION) += emul_rtc.o
 obj-$(CONFIG_RTC_FTRTC010) += ftrtc010.o
 obj-$(CONFIG_SANDBOX) += i2c_rtc_emul.o
 obj-$(CONFIG_RTC_IMXDI) += imxdi.o
diff --git a/drivers/rtc/emul_rtc.c b/drivers/rtc/emul_rtc.c
new file mode 100644
index 0000000000..f291d19ab5
--- /dev/null
+++ b/drivers/rtc/emul_rtc.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright 2020, Heinrich Schuchardt <xypron.glpk at gmx.de>
+ *
+ * This driver emulates a real time clock based on timer ticks.
+ */
+
+#include <common.h>
+#include <div64.h>
+#include <dm.h>
+#include <rtc.h>
+
+/**
+ * struct emul_rtc - private data for emulated RTC driver
+ */
+struct emul_rtc {
+	/**
+	 * @offset_us: microseconds from 1970-01-01 to timer_get_us() base
+	 */
+	u64 offset_us;
+	/**
+	 * @isdst: daylight saving time
+	 */
+	int isdst;
+};
+
+static int emul_rtc_get(struct udevice *dev, struct rtc_time *time)
+{
+	struct emul_rtc *priv = dev_get_priv(dev);
+	u64 now;
+
+	if (!priv->offset_us) {
+		/* Assume it is 2021-01-11T00:00:00Z */
+		priv->offset_us = 1610323200000000ULL - timer_get_us();
+		priv->isdst = -1;
+	}
+
+	now = timer_get_us() + priv->offset_us;
+	do_div(now, 1000000);
+	rtc_to_tm(now, time);
+	time->tm_isdst = priv->isdst;
+
+	return 0;
+}
+
+static int emul_rtc_set(struct udevice *dev, const struct rtc_time *time)
+{
+	struct emul_rtc *priv = dev_get_priv(dev);
+
+	if (time->tm_year < 1970)
+		return -EINVAL;
+
+	priv->offset_us = rtc_mktime(time) * 1000000ULL - timer_get_us();
+
+	if (time->tm_isdst > 0)
+		priv->isdst = 1;
+	else if (time->tm_isdst < 0)
+		priv->isdst = -1;
+	else
+		priv->isdst = 0;
+
+	return 0;
+}
+
+static const struct rtc_ops emul_rtc_ops = {
+	.get = emul_rtc_get,
+	.set = emul_rtc_set,
+};
+
+U_BOOT_DRIVER(rtc_emul) = {
+	.name	= "emulated RTC",
+	.id	= UCLASS_RTC,
+	.ops	= &emul_rtc_ops,
+	.priv_auto_alloc_size = sizeof(struct emul_rtc),
+};
+
+U_BOOT_DEVICE(rtc_emul) = {
+	.name	= "emulated RTC",
+};
--
2.28.0