rtc: Add Realtek RTD1295

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>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

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

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

drivers/rtc/rtc-rtd119x.c

@@ -0,0 +1,242 @@
+/*
+ * 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 int base_year;
+};
+
+static inline int rtd119x_rtc_days_in_year(int year)
+{
+	return 365 + (is_leap_year(year) ? 1 : 0);
+}
+
+static void rtd119x_rtc_reset(struct device *dev)
+{
+	struct rtd119x_rtc *data = dev_get_drvdata(dev);
+	u32 val;
+
+	val = readl_relaxed(data->base + RTD_RTCCR);
+	val |= RTD_RTCCR_RTCRST;
+	writel_relaxed(val, data->base + RTD_RTCCR);
+
+	val &= ~RTD_RTCCR_RTCRST;
+	writel(val, data->base + RTD_RTCCR);
+}
+
+static void rtd119x_rtc_set_enabled(struct device *dev, bool enable)
+{
+	struct rtd119x_rtc *data = dev_get_drvdata(dev);
+	u32 val;
+
+	val = readl_relaxed(data->base + RTD_RTCEN);
+	if (enable) {
+		if ((val & RTD_RTCEN_RTCEN_MASK) == 0x5a)
+			return;
+		writel_relaxed(0x5a, data->base + RTD_RTCEN);
+	} else {
+		writel_relaxed(0, data->base + RTD_RTCEN);
+	}
+}
+
+static int rtd119x_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rtd119x_rtc *data = dev_get_drvdata(dev);
+	s32 day;
+	u32 sec;
+	unsigned int year;
+	int tries = 0;
+
+	while (true) {
+		tm->tm_sec = (readl_relaxed(data->base + RTD_RTCSEC) & RTD_RTCSEC_RTCSEC_MASK) >> 1;
+		tm->tm_min  = readl_relaxed(data->base + RTD_RTCMIN) & RTD_RTCMIN_RTCMIN_MASK;
+		tm->tm_hour = readl_relaxed(data->base + RTD_RTCHR) & RTD_RTCHR_RTCHR_MASK;
+		day  =  readl_relaxed(data->base + RTD_RTCDATE1) & RTD_RTCDATE1_RTCDATE1_MASK;
+		day |= (readl_relaxed(data->base + RTD_RTCDATE2) & RTD_RTCDATE2_RTCDATE2_MASK) << 8;
+		sec  = (readl_relaxed(data->base + RTD_RTCSEC) & RTD_RTCSEC_RTCSEC_MASK) >> 1;
+		tries++;
+
+		if (sec == tm->tm_sec)
+			break;
+
+		if (tries >= 3)
+			return -EINVAL;
+	}
+	if (tries > 1)
+		dev_dbg(dev, "%s: needed %i tries\n", __func__, tries);
+
+	year = data->base_year;
+	while (day >= rtd119x_rtc_days_in_year(year)) {
+		day -= rtd119x_rtc_days_in_year(year);
+		year++;
+	}
+	tm->tm_year = year - 1900;
+	tm->tm_yday = day;
+
+	tm->tm_mon = 0;
+	while (day >= rtc_month_days(tm->tm_mon, year)) {
+		day -= rtc_month_days(tm->tm_mon, year);
+		tm->tm_mon++;
+	}
+	tm->tm_mday = day + 1;
+
+	return 0;
+}
+
+static int rtd119x_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct rtd119x_rtc *data = dev_get_drvdata(dev);
+	unsigned int day;
+	int i;
+
+	if (1900 + tm->tm_year < data->base_year)
+		return -EINVAL;
+
+	day = 0;
+	for (i = data->base_year; i < 1900 + tm->tm_year; i++)
+		day += rtd119x_rtc_days_in_year(i);
+
+	day += tm->tm_yday;
+	if (day > 0x7fff)
+		return -EINVAL;
+
+	rtd119x_rtc_set_enabled(dev, false);
+
+	writel_relaxed((tm->tm_sec << 1) & RTD_RTCSEC_RTCSEC_MASK, data->base + RTD_RTCSEC);
+	writel_relaxed(tm->tm_min & RTD_RTCMIN_RTCMIN_MASK, data->base + RTD_RTCMIN);
+	writel_relaxed(tm->tm_hour & RTD_RTCHR_RTCHR_MASK, data->base + RTD_RTCHR);
+	writel_relaxed(day & RTD_RTCDATE1_RTCDATE1_MASK, data->base + RTD_RTCDATE1);
+	writel_relaxed((day >> 8) & RTD_RTCDATE2_RTCDATE2_MASK, data->base + RTD_RTCDATE2);
+
+	rtd119x_rtc_set_enabled(dev, true);
+
+	return 0;
+}
+
+static const struct rtc_class_ops rtd119x_rtc_ops = {
+	.read_time	= rtd119x_rtc_read_time,
+	.set_time	= rtd119x_rtc_set_time,
+};
+
+static const struct of_device_id rtd119x_rtc_dt_ids[] = {
+	 { .compatible = "realtek,rtd1295-rtc" },
+	 { }
+};
+
+static int rtd119x_rtc_probe(struct platform_device *pdev)
+{
+	struct rtd119x_rtc *data;
+	struct resource *res;
+	u32 val;
+	int ret;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, data);
+	data->base_year = 2014;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	data->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(data->base))
+		return PTR_ERR(data->base);
+
+	data->clk = of_clk_get(pdev->dev.of_node, 0);
+	if (IS_ERR(data->clk))
+		return PTR_ERR(data->clk);
+
+	ret = clk_prepare_enable(data->clk);
+	if (ret) {
+		clk_put(data->clk);
+		return ret;
+	}
+
+	val = readl_relaxed(data->base + RTD_RTCACR);
+	if (!(val & RTD_RTCACR_RTCPWR)) {
+		writel_relaxed(RTD_RTCACR_RTCPWR, data->base + RTD_RTCACR);
+
+		rtd119x_rtc_reset(&pdev->dev);
+
+		writel_relaxed(0, data->base + RTD_RTCMIN);
+		writel_relaxed(0, data->base + RTD_RTCHR);
+		writel_relaxed(0, data->base + RTD_RTCDATE1);
+		writel_relaxed(0, data->base + RTD_RTCDATE2);
+	}
+
+	rtd119x_rtc_set_enabled(&pdev->dev, true);
+
+	data->rtcdev = devm_rtc_device_register(&pdev->dev, "rtc",
+						&rtd119x_rtc_ops, THIS_MODULE);
+	if (IS_ERR(data->rtcdev)) {
+		dev_err(&pdev->dev, "failed to register rtc device");
+		clk_disable_unprepare(data->clk);
+		clk_put(data->clk);
+		return PTR_ERR(data->rtcdev);
+	}
+
+	return 0;
+}
+
+static int rtd119x_rtc_remove(struct platform_device *pdev)
+{
+	struct rtd119x_rtc *data = platform_get_drvdata(pdev);
+
+	rtd119x_rtc_set_enabled(&pdev->dev, false);
+
+	clk_disable_unprepare(data->clk);
+	clk_put(data->clk);
+
+	return 0;
+}
+
+static struct platform_driver rtd119x_rtc_driver = {
+	.probe = rtd119x_rtc_probe,
+	.remove = rtd119x_rtc_remove,
+	.driver = {
+		.name = "rtd1295-rtc",
+		.of_match_table	= rtd119x_rtc_dt_ids,
+	},
+};
+builtin_platform_driver(rtd119x_rtc_driver);