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>

3 files changed, 251 insertions, 0 deletions

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index a76a26e2292a..e0e58f3b1420 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 d995d49d8218..7230014c92af 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..b233559d950b
--- /dev/null
+++ b/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);