[PATCH 2/3] rtc: Add StarFive JH7110 RTC driver

[Owen O'Hehir <oo.hehir@gmail.com>]

From: "ziv.xu" <ziv.xu@starfivetech.com>

Add a driver for the RTC in the always-on domain of the StarFive JH7110
SoC. It supports time, alarm with wakeup, and the frequency offset.

Signed-off-by: ziv.xu <ziv.xu@starfivetech.com>
Signed-off-by: Hal Feng <hal.feng@starfivetech.com>
[Owen: rework of the StarFive vendor driver for mainline: drop hardware
 calibration & the default time set in probe, use the generic wake IRQ
 helpers, wait for the update bit in set_time, re-read a time that rolls
 over during the read, round the offset to the nearest step & follow the
 sysfs offset sign, enable the 32k counter clock]
Co-developed-by: Owen O'Hehir <oo.hehir@gmail.com>
Signed-off-by: Owen O'Hehir <oo.hehir@gmail.com>
---
 drivers/rtc/Kconfig      |  11 ++
 drivers/rtc/Makefile     |   1 +
 drivers/rtc/rtc-jh7110.c | 324 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 336 insertions(+)
 create mode 100644 drivers/rtc/rtc-jh7110.c

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index 73ec9230e..332f2e022 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1807,6 +1807,17 @@ config RTC_DRV_MPC5121
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-mpc5121.
 
+config RTC_DRV_JH7110
+	tristate "StarFive JH7110 RTC"
+	depends on ARCH_STARFIVE || COMPILE_TEST
+	help
+	  If you say yes here you get support for the RTC in the always-on
+	  domain of StarFive JH7110 SoCs, with alarm and frequency offset
+	  support.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called rtc-jh7110.
+
 config RTC_DRV_JZ4740
 	tristate "Ingenic JZ4740 SoC"
 	depends on MIPS || COMPILE_TEST
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 46f1a0fc2..a5cddb8d8 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_RTC_DRV_IMX_BBM_SCMI)	+= rtc-imx-sm-bbm.o
 obj-$(CONFIG_RTC_DRV_ISL12022)	+= rtc-isl12022.o
 obj-$(CONFIG_RTC_DRV_ISL12026)	+= rtc-isl12026.o
 obj-$(CONFIG_RTC_DRV_ISL1208)	+= rtc-isl1208.o
+obj-$(CONFIG_RTC_DRV_JH7110)	+= rtc-jh7110.o
 obj-$(CONFIG_RTC_DRV_JZ4740)	+= rtc-jz4740.o
 obj-$(CONFIG_RTC_DRV_LOONGSON)	+= rtc-loongson.o
 obj-$(CONFIG_RTC_DRV_LP8788)	+= rtc-lp8788.o
diff --git a/drivers/rtc/rtc-jh7110.c b/drivers/rtc/rtc-jh7110.c
new file mode 100644
index 000000000..f7129b7ac
--- /dev/null
+++ b/drivers/rtc/rtc-jh7110.c
@@ -0,0 +1,324 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RTC driver for the StarFive JH7110 SoC
+ *
+ * Copyright (C) 2021 StarFive Technology Co., Ltd.
+ */
+
+#include <linux/bcd.h>
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/math64.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_wakeirq.h>
+#include <linux/reset.h>
+#include <linux/rtc.h>
+
+#define JH7110_RTC_CFG			0x00
+#define  JH7110_RTC_CFG_ENABLE		BIT(0)
+#define  JH7110_RTC_CFG_CAL_SEL_HW	BIT(2)
+#define  JH7110_RTC_CFG_HOUR_24H	BIT(3)
+#define JH7110_RTC_SW_CAL_VALUE		0x04
+#define JH7110_RTC_IRQ_EN		0x10
+#define JH7110_RTC_IRQ_EVENT		0x14
+#define  JH7110_RTC_IRQ_ALARM		BIT(4)
+#define  JH7110_RTC_IRQ_ALL		GENMASK(4, 0)
+#define  JH7110_RTC_EVENT_UPDATE	BIT(31)
+#define JH7110_RTC_CAL_VALUE		0x24
+#define JH7110_RTC_CFG_TIME		0x28
+#define JH7110_RTC_CFG_DATE		0x2c
+#define JH7110_RTC_ACT_TIME		0x34
+#define JH7110_RTC_ACT_DATE		0x38
+#define JH7110_RTC_TIME			0x3c
+#define JH7110_RTC_DATE			0x40
+
+#define JH7110_RTC_TIME_SEC		GENMASK(6, 0)
+#define JH7110_RTC_TIME_MIN		GENMASK(13, 7)
+#define JH7110_RTC_TIME_HOUR		GENMASK(20, 14)
+#define JH7110_RTC_DATE_DAY		GENMASK(5, 0)
+#define JH7110_RTC_DATE_MON		GENMASK(10, 6)
+#define JH7110_RTC_DATE_YEAR		GENMASK(18, 11)
+
+#define JH7110_RTC_CAL_MASK		GENMASK(15, 0)
+#define JH7110_RTC_TICKS_PER_SEC	32768
+
+#define JH7110_RTC_SYNC_TIMEOUT_US	1000
+
+struct jh7110_rtc {
+	struct rtc_device *rtc;
+	void __iomem *base;
+};
+
+static void jh7110_rtc_reg2tm(struct rtc_time *tm, u32 time, u32 date)
+{
+	tm->tm_sec = bcd2bin(FIELD_GET(JH7110_RTC_TIME_SEC, time));
+	tm->tm_min = bcd2bin(FIELD_GET(JH7110_RTC_TIME_MIN, time));
+	tm->tm_hour = bcd2bin(FIELD_GET(JH7110_RTC_TIME_HOUR, time));
+	tm->tm_mday = bcd2bin(FIELD_GET(JH7110_RTC_DATE_DAY, date));
+	tm->tm_mon = bcd2bin(FIELD_GET(JH7110_RTC_DATE_MON, date)) - 1;
+	tm->tm_year = bcd2bin(FIELD_GET(JH7110_RTC_DATE_YEAR, date)) + 100;
+}
+
+static u32 jh7110_rtc_tm2time(struct rtc_time *tm)
+{
+	return FIELD_PREP(JH7110_RTC_TIME_SEC, bin2bcd(tm->tm_sec)) |
+	       FIELD_PREP(JH7110_RTC_TIME_MIN, bin2bcd(tm->tm_min)) |
+	       FIELD_PREP(JH7110_RTC_TIME_HOUR, bin2bcd(tm->tm_hour));
+}
+
+static u32 jh7110_rtc_tm2date(struct rtc_time *tm)
+{
+	return FIELD_PREP(JH7110_RTC_DATE_DAY, bin2bcd(tm->tm_mday)) |
+	       FIELD_PREP(JH7110_RTC_DATE_MON, bin2bcd(tm->tm_mon + 1)) |
+	       FIELD_PREP(JH7110_RTC_DATE_YEAR, bin2bcd(tm->tm_year - 100));
+}
+
+static int jh7110_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct jh7110_rtc *jrtc = dev_get_drvdata(dev);
+	u32 time, date;
+
+	/*
+	 * re-read if the time rolled over between reading TIME & DATE, since
+	 * that rollover can also change the date.
+	 */
+	do {
+		time = readl(jrtc->base + JH7110_RTC_TIME);
+		date = readl(jrtc->base + JH7110_RTC_DATE);
+	} while (time != readl(jrtc->base + JH7110_RTC_TIME));
+
+	jh7110_rtc_reg2tm(tm, time, date);
+
+	return 0;
+}
+
+static int jh7110_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct jh7110_rtc *jrtc = dev_get_drvdata(dev);
+	u32 val;
+
+	writel(jh7110_rtc_tm2time(tm), jrtc->base + JH7110_RTC_CFG_TIME);
+	writel(jh7110_rtc_tm2date(tm), jrtc->base + JH7110_RTC_CFG_DATE);
+
+	/*
+	 * The counter loads CFG_TIME & CFG_DATE on this pulse; the bit appears
+	 * to read back as 1 until the load is done.
+	 */
+	writel(JH7110_RTC_EVENT_UPDATE, jrtc->base + JH7110_RTC_IRQ_EVENT);
+
+	return readl_poll_timeout(jrtc->base + JH7110_RTC_IRQ_EVENT, val,
+				  !(val & JH7110_RTC_EVENT_UPDATE), 10,
+				  JH7110_RTC_SYNC_TIMEOUT_US);
+}
+
+static int jh7110_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct jh7110_rtc *jrtc = dev_get_drvdata(dev);
+	u32 val;
+
+	val = readl(jrtc->base + JH7110_RTC_IRQ_EN);
+	if (enabled)
+		val |= JH7110_RTC_IRQ_ALARM;
+	else
+		val &= ~JH7110_RTC_IRQ_ALARM;
+	writel(val, jrtc->base + JH7110_RTC_IRQ_EN);
+
+	return 0;
+}
+
+static int jh7110_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct jh7110_rtc *jrtc = dev_get_drvdata(dev);
+
+	jh7110_rtc_reg2tm(&alrm->time, readl(jrtc->base + JH7110_RTC_ACT_TIME),
+			  readl(jrtc->base + JH7110_RTC_ACT_DATE));
+	alrm->enabled = !!(readl(jrtc->base + JH7110_RTC_IRQ_EN) & JH7110_RTC_IRQ_ALARM);
+
+	return 0;
+}
+
+static int jh7110_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct jh7110_rtc *jrtc = dev_get_drvdata(dev);
+	u32 val;
+	int ret;
+
+	jh7110_rtc_alarm_irq_enable(dev, 0);
+	writel(jh7110_rtc_tm2time(&alrm->time), jrtc->base + JH7110_RTC_ACT_TIME);
+	writel(jh7110_rtc_tm2date(&alrm->time), jrtc->base + JH7110_RTC_ACT_DATE);
+	writel(JH7110_RTC_IRQ_ALARM, jrtc->base + JH7110_RTC_IRQ_EVENT);
+
+	ret = readl_poll_timeout(jrtc->base + JH7110_RTC_IRQ_EVENT, val,
+				 !(val & JH7110_RTC_IRQ_ALARM), 10,
+				 JH7110_RTC_SYNC_TIMEOUT_US);
+	if (ret)
+		return ret;
+
+	return jh7110_rtc_alarm_irq_enable(dev, alrm->enabled);
+}
+
+/*
+ * 1 sec for the RTC = CAL_VALUE + 1 cycles of the 32.768 kHz clock.
+ * Default of 0x7fff = exactly one second.
+ * Each step of CAL_VALUE changes the rate by 1/32768, about 30.5 ppm.
+ */
+static int jh7110_rtc_read_offset(struct device *dev, long *offset)
+{
+	struct jh7110_rtc *jrtc = dev_get_drvdata(dev);
+	s64 ticks;
+
+	ticks = (readl(jrtc->base + JH7110_RTC_CAL_VALUE) & JH7110_RTC_CAL_MASK) + 1;
+	*offset = DIV_S64_ROUND_CLOSEST((ticks - JH7110_RTC_TICKS_PER_SEC) * NSEC_PER_SEC,
+					JH7110_RTC_TICKS_PER_SEC);
+
+	return 0;
+}
+
+static int jh7110_rtc_set_offset(struct device *dev, long offset)
+{
+	struct jh7110_rtc *jrtc = dev_get_drvdata(dev);
+	s64 ticks;
+	u32 val;
+
+	if (offset < -NSEC_PER_SEC || offset > NSEC_PER_SEC)
+		return -ERANGE;
+
+	ticks = JH7110_RTC_TICKS_PER_SEC +
+		DIV_S64_ROUND_CLOSEST((s64)offset * JH7110_RTC_TICKS_PER_SEC, NSEC_PER_SEC);
+	if (ticks < 1 || ticks > JH7110_RTC_CAL_MASK + 1)
+		return -ERANGE;
+
+	writel(ticks - 1, jrtc->base + JH7110_RTC_SW_CAL_VALUE);
+	val = readl(jrtc->base + JH7110_RTC_CFG);
+	writel(val & ~JH7110_RTC_CFG_CAL_SEL_HW, jrtc->base + JH7110_RTC_CFG);
+
+	return 0;
+}
+
+static irqreturn_t jh7110_rtc_irq(int irq, void *data)
+{
+	struct jh7110_rtc *jrtc = data;
+	u32 events, val;
+
+	events = readl(jrtc->base + JH7110_RTC_IRQ_EVENT) &
+		 readl(jrtc->base + JH7110_RTC_IRQ_EN) & JH7110_RTC_IRQ_ALL;
+	if (!events)
+		return IRQ_NONE;
+
+	writel(events, jrtc->base + JH7110_RTC_IRQ_EVENT);
+	if (readl_poll_timeout_atomic(jrtc->base + JH7110_RTC_IRQ_EVENT, val,
+				      !(val & events), 0, JH7110_RTC_SYNC_TIMEOUT_US))
+		dev_warn_ratelimited(&jrtc->rtc->dev, "interrupt events 0x%x not cleared\n",
+				     events);
+
+	if (events & JH7110_RTC_IRQ_ALARM)
+		rtc_update_irq(jrtc->rtc, 1, RTC_AF | RTC_IRQF);
+
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops jh7110_rtc_ops = {
+	.read_time		= jh7110_rtc_read_time,
+	.set_time		= jh7110_rtc_set_time,
+	.read_alarm		= jh7110_rtc_read_alarm,
+	.set_alarm		= jh7110_rtc_set_alarm,
+	.alarm_irq_enable	= jh7110_rtc_alarm_irq_enable,
+	.read_offset		= jh7110_rtc_read_offset,
+	.set_offset		= jh7110_rtc_set_offset,
+};
+
+static int jh7110_rtc_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct reset_control *rst;
+	struct jh7110_rtc *jrtc;
+	struct clk *clk;
+	int irq, ret;
+	u32 val;
+
+	jrtc = devm_kzalloc(dev, sizeof(*jrtc), GFP_KERNEL);
+	if (!jrtc)
+		return -ENOMEM;
+
+	jrtc->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(jrtc->base))
+		return PTR_ERR(jrtc->base);
+
+	clk = devm_clk_get_enabled(dev, "apb");
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "failed to enable apb clock\n");
+
+	clk = devm_clk_get_enabled(dev, "cal");
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "failed to enable cal clock\n");
+
+	clk = devm_clk_get_enabled(dev, "32k");
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "failed to enable 32k clock\n");
+
+	/* Never asserted again, as that would stop the clock & lose the time */
+	rst = devm_reset_control_array_get_exclusive(dev);
+	if (IS_ERR(rst))
+		return dev_err_probe(dev, PTR_ERR(rst), "failed to get resets\n");
+
+	ret = reset_control_deassert(rst);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to deassert resets\n");
+
+	irq = platform_get_irq_byname(pdev, "rtc");
+	if (irq < 0)
+		return irq;
+
+	jrtc->rtc = devm_rtc_allocate_device(dev);
+	if (IS_ERR(jrtc->rtc))
+		return PTR_ERR(jrtc->rtc);
+
+	platform_set_drvdata(pdev, jrtc);
+
+	jrtc->rtc->ops = &jh7110_rtc_ops;
+	jrtc->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
+	jrtc->rtc->range_max = RTC_TIMESTAMP_END_2099;
+
+	val = readl(jrtc->base + JH7110_RTC_CFG);
+	writel(val | JH7110_RTC_CFG_HOUR_24H | JH7110_RTC_CFG_ENABLE,
+	       jrtc->base + JH7110_RTC_CFG);
+
+	ret = devm_request_irq(dev, irq, jh7110_rtc_irq, 0, dev_name(dev), jrtc);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to request irq\n");
+
+	ret = devm_device_init_wakeup(dev);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to init wakeup\n");
+
+	ret = devm_pm_set_wake_irq(dev, irq);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to set wake irq\n");
+
+	return devm_rtc_register_device(jrtc->rtc);
+}
+
+static const struct of_device_id jh7110_rtc_of_match[] = {
+	{ .compatible = "starfive,jh7110-rtc" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, jh7110_rtc_of_match);
+
+static struct platform_driver jh7110_rtc_driver = {
+	.driver = {
+		.name = "jh7110-rtc",
+		.of_match_table = jh7110_rtc_of_match,
+	},
+	.probe = jh7110_rtc_probe,
+};
+module_platform_driver(jh7110_rtc_driver);
+
+MODULE_AUTHOR("Samin Guo <samin.guo@starfivetech.com>");
+MODULE_AUTHOR("Hal Feng <hal.feng@starfivetech.com>");
+MODULE_DESCRIPTION("StarFive JH7110 RTC driver");
+MODULE_LICENSE("GPL");
-- 
2.43.0