VisionFive2 Linux kernel

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index ce723dc54aa4..e6205f7a7d59 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1296,6 +1296,14 @@ config RTC_DRV_CROS_EC
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-cros-ec.
 
+config RTC_DRV_NTXEC
+	tristate "Netronix embedded controller RTC"
+	depends on MFD_NTXEC
+	help
+	  Say yes here if you want to support the RTC functionality of the
+	  embedded controller found in certain e-book readers designed by the
+	  original design manufacturer Netronix.
+
 comment "on-CPU RTC drivers"
 
 config RTC_DRV_ASM9260
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 4e930183c170..2dd0dd956b0e 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -108,6 +108,7 @@ obj-$(CONFIG_RTC_DRV_MT7622)	+= rtc-mt7622.o
 obj-$(CONFIG_RTC_DRV_MV)	+= rtc-mv.o
 obj-$(CONFIG_RTC_DRV_MXC)	+= rtc-mxc.o
 obj-$(CONFIG_RTC_DRV_MXC_V2)	+= rtc-mxc_v2.o
+obj-$(CONFIG_RTC_DRV_NTXEC)	+= rtc-ntxec.o
 obj-$(CONFIG_RTC_DRV_OMAP)	+= rtc-omap.o
 obj-$(CONFIG_RTC_DRV_OPAL)	+= rtc-opal.o
 obj-$(CONFIG_RTC_DRV_PALMAS)	+= rtc-palmas.o
diff --git a/drivers/rtc/rtc-ntxec.c b/drivers/rtc/rtc-ntxec.c
new file mode 100644
index 000000000000..850ca49186fd
--- /dev/null
+++ b/drivers/rtc/rtc-ntxec.c
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * The Netronix embedded controller is a microcontroller found in some
+ * e-book readers designed by the original design manufacturer Netronix, Inc.
+ * It contains RTC, battery monitoring, system power management, and PWM
+ * functionality.
+ *
+ * This driver implements access to the RTC time and date.
+ *
+ * Copyright 2020 Jonathan Neuschäfer <j.neuschaefer@gmx.net>
+ */
+
+#include <linux/mfd/ntxec.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/types.h>
+
+struct ntxec_rtc {
+	struct device *dev;
+	struct ntxec *ec;
+};
+
+#define NTXEC_REG_WRITE_YEAR	0x10
+#define NTXEC_REG_WRITE_MONTH	0x11
+#define NTXEC_REG_WRITE_DAY	0x12
+#define NTXEC_REG_WRITE_HOUR	0x13
+#define NTXEC_REG_WRITE_MINUTE	0x14
+#define NTXEC_REG_WRITE_SECOND	0x15
+
+#define NTXEC_REG_READ_YEAR_MONTH	0x20
+#define NTXEC_REG_READ_MDAY_HOUR	0x21
+#define NTXEC_REG_READ_MINUTE_SECOND	0x23
+
+static int ntxec_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct ntxec_rtc *rtc = dev_get_drvdata(dev);
+	unsigned int value;
+	int res;
+
+retry:
+	res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_MINUTE_SECOND, &value);
+	if (res < 0)
+		return res;
+
+	tm->tm_min = value >> 8;
+	tm->tm_sec = value & 0xff;
+
+	res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_MDAY_HOUR, &value);
+	if (res < 0)
+		return res;
+
+	tm->tm_mday = value >> 8;
+	tm->tm_hour = value & 0xff;
+
+	res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_YEAR_MONTH, &value);
+	if (res < 0)
+		return res;
+
+	tm->tm_year = (value >> 8) + 100;
+	tm->tm_mon = (value & 0xff) - 1;
+
+	/*
+	 * Read the minutes/seconds field again. If it changed since the first
+	 * read, we can't assume that the values read so far are consistent,
+	 * and should start from the beginning.
+	 */
+	res = regmap_read(rtc->ec->regmap, NTXEC_REG_READ_MINUTE_SECOND, &value);
+	if (res < 0)
+		return res;
+
+	if (tm->tm_min != value >> 8 || tm->tm_sec != (value & 0xff))
+		goto retry;
+
+	return 0;
+}
+
+static int ntxec_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct ntxec_rtc *rtc = dev_get_drvdata(dev);
+
+	/*
+	 * To avoid time overflows while we're writing the full date/time,
+	 * set the seconds field to zero before doing anything else. For the
+	 * next 59 seconds (plus however long it takes until the RTC's next
+	 * update of the second field), the seconds field will not overflow
+	 * into the other fields.
+	 */
+	struct reg_sequence regs[] = {
+		{ NTXEC_REG_WRITE_SECOND, ntxec_reg8(0) },
+		{ NTXEC_REG_WRITE_YEAR, ntxec_reg8(tm->tm_year - 100) },
+		{ NTXEC_REG_WRITE_MONTH, ntxec_reg8(tm->tm_mon + 1) },
+		{ NTXEC_REG_WRITE_DAY, ntxec_reg8(tm->tm_mday) },
+		{ NTXEC_REG_WRITE_HOUR, ntxec_reg8(tm->tm_hour) },
+		{ NTXEC_REG_WRITE_MINUTE, ntxec_reg8(tm->tm_min) },
+		{ NTXEC_REG_WRITE_SECOND, ntxec_reg8(tm->tm_sec) },
+	};
+
+	return regmap_multi_reg_write(rtc->ec->regmap, regs, ARRAY_SIZE(regs));
+}
+
+static const struct rtc_class_ops ntxec_rtc_ops = {
+	.read_time = ntxec_read_time,
+	.set_time = ntxec_set_time,
+};
+
+static int ntxec_rtc_probe(struct platform_device *pdev)
+{
+	struct rtc_device *dev;
+	struct ntxec_rtc *rtc;
+
+	pdev->dev.of_node = pdev->dev.parent->of_node;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+
+	rtc->dev = &pdev->dev;
+	rtc->ec = dev_get_drvdata(pdev->dev.parent);
+	platform_set_drvdata(pdev, rtc);
+
+	dev = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(dev))
+		return PTR_ERR(dev);
+
+	dev->ops = &ntxec_rtc_ops;
+	dev->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	dev->range_max = 9025257599LL; /* 2255-12-31 23:59:59 */
+
+	return devm_rtc_register_device(dev);
+}
+
+static struct platform_driver ntxec_rtc_driver = {
+	.driver = {
+		.name = "ntxec-rtc",
+	},
+	.probe = ntxec_rtc_probe,
+};
+module_platform_driver(ntxec_rtc_driver);
+
+MODULE_AUTHOR("Jonathan Neuschäfer <j.neuschaefer@gmx.net>");
+MODULE_DESCRIPTION("RTC driver for Netronix EC");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ntxec-rtc");