Based on QNAP's arch/arm/mach-rtk119x/driver/rtk_rtc_drv.c code and
mach-rtk119x/driver/dc2vo/fpga/include/mis_reg.h register definitions.

The base year 2014 was observed on all of Zidoo X9S, ProBox2 Ava and
Beelink Lake I.

Signed-off-by: Andreas Färber <afaerber@suse.de>
---
 v1 -> v2:
 * Dropped open/release in favor of probe/remove (Alexandre)
 * read_time: Reordered register accesses (Alexandre)
 * read_time/set_time: Refactored day calculations to avoid time64_t (Alexandre)
 * read_time: Retry if seconds change (Alexandre)
 * probe: Added missing RTCACR initialization code
 * set_time: Fixed year check (off by 1900)
 * set_time: Fixed new seconds (off by factor two)
 * Cleaned up debug output (Andrew)
 * Added spinlocks around register accesses
 * Added masks for register fields
 
 drivers/rtc/Kconfig       |   8 ++
 drivers/rtc/Makefile      |   1 +
 drivers/rtc/rtc-rtd119x.c | 254 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 263 insertions(+)
 create mode 100644 drivers/rtc/rtc-rtd119x.c

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 22efa21b1d81..d5a46f311ecb 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig

@@ -1765,6 +1765,14 @@ config RTC_DRV_CPCAP
 	   Say y here for CPCAP rtc found on some Motorola phones
 	   and tablets such as Droid 4.
 
+config RTC_DRV_RTD119X
+	bool "Realtek RTD129x RTC"
+	depends on ARCH_REALTEK || COMPILE_TEST
+	default ARCH_REALTEK
+	help
+	  If you say yes here, you get support for the RTD1295 SoC
+	  Real Time Clock.
+
 comment "HID Sensor RTC drivers"
 
 config RTC_DRV_HID_SENSOR_TIME

diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index acd366b41c85..55a0a5ca45b0 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile

@@ -131,6 +131,7 @@ obj-$(CONFIG_RTC_DRV_RP5C01)	+= rtc-rp5c01.o
 obj-$(CONFIG_RTC_DRV_RS5C313)	+= rtc-rs5c313.o
 obj-$(CONFIG_RTC_DRV_RS5C348)	+= rtc-rs5c348.o
 obj-$(CONFIG_RTC_DRV_RS5C372)	+= rtc-rs5c372.o
+obj-$(CONFIG_RTC_DRV_RTD119X)	+= rtc-rtd119x.o
 obj-$(CONFIG_RTC_DRV_RV3029C2)	+= rtc-rv3029c2.o
 obj-$(CONFIG_RTC_DRV_RV8803)	+= rtc-rv8803.o
 obj-$(CONFIG_RTC_DRV_RX4581)	+= rtc-rx4581.o

diff --git a/drivers/rtc/rtc-rtd119x.c b/drivers/rtc/rtc-rtd119x.c
new file mode 100644
index 000000000000..27fa68a5af30
--- /dev/null
+++ b/drivers/rtc/rtc-rtd119x.c

@@ -0,0 +1,254 @@
+/*
+ * Realtek RTD129x RTC
+ *
+ * Copyright (c) 2017 Andreas Färber
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/spinlock.h>
+
+#define RTD_RTCSEC		0x00
+#define RTD_RTCMIN		0x04
+#define RTD_RTCHR		0x08
+#define RTD_RTCDATE1		0x0c
+#define RTD_RTCDATE2		0x10
+#define RTD_RTCACR		0x28
+#define RTD_RTCEN		0x2c
+#define RTD_RTCCR		0x30
+
+#define RTD_RTCSEC_RTCSEC_MASK		0x7f
+
+#define RTD_RTCMIN_RTCMIN_MASK		0x3f
+
+#define RTD_RTCHR_RTCHR_MASK		0x1f
+
+#define RTD_RTCDATE1_RTCDATE1_MASK	0xff
+
+#define RTD_RTCDATE2_RTCDATE2_MASK	0x7f
+
+#define RTD_RTCACR_RTCPWR		BIT(7)
+
+#define RTD_RTCEN_RTCEN_MASK		0xff
+
+#define RTD_RTCCR_RTCRST		BIT(6)
+
+struct rtd119x_rtc {
+	void __iomem *base;
+	struct clk *clk;
+	struct rtc_device *rtcdev;
+	unsigned base_year;
+	spinlock_t lock;