rtc: Add driver for Microchip PolarFire SoC

Add support for the built-in RTC on Microchip PolarFire SoC
Co-Developed-by: Daire McNamara <daire.mcnamara@microchip.com>
Signed-off-by: Daire McNamara <daire.mcnamara@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220601123320.2861043-2-conor.dooley@microchip.com

drivers/rtc/Kconfig

@@ -1973,4 +1973,14 @@ config RTC_DRV_MSC313
 	  This driver can also be built as a module, if so, the module
 	  will be called "rtc-msc313".
 
+config RTC_DRV_POLARFIRE_SOC
+	tristate "Microchip PolarFire SoC built-in RTC"
+	depends on SOC_MICROCHIP_POLARFIRE
+	help
+	  If you say yes here you will get support for the
+	  built-in RTC on Polarfire SoC.
+
+	  This driver can also be built as a module, if so, the module
+	  will be called "rtc-mpfs".
+
 endif # RTC_CLASS

drivers/rtc/Makefile

@@ -130,6 +130,7 @@ obj-$(CONFIG_RTC_DRV_PIC32)	+= rtc-pic32.o
 obj-$(CONFIG_RTC_DRV_PL030)	+= rtc-pl030.o
 obj-$(CONFIG_RTC_DRV_PL031)	+= rtc-pl031.o
 obj-$(CONFIG_RTC_DRV_PM8XXX)	+= rtc-pm8xxx.o
+obj-$(CONFIG_RTC_DRV_POLARFIRE_SOC)	+= rtc-mpfs.o
 obj-$(CONFIG_RTC_DRV_PS3)	+= rtc-ps3.o
 obj-$(CONFIG_RTC_DRV_PXA)	+= rtc-pxa.o
 obj-$(CONFIG_RTC_DRV_R7301)	+= rtc-r7301.o

drivers/rtc/rtc-mpfs.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Microchip MPFS RTC driver
+ *
+ * Copyright (c) 2021-2022 Microchip Corporation. All rights reserved.
+ *
+ * Author: Daire McNamara <daire.mcnamara@microchip.com>
+ *         & Conor Dooley <conor.dooley@microchip.com>
+ */
+#include "linux/bits.h"
+#include "linux/iopoll.h"
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm_wakeirq.h>
+#include <linux/slab.h>
+#include <linux/rtc.h>
+
+#define CONTROL_REG		0x00
+#define MODE_REG		0x04
+#define PRESCALER_REG		0x08
+#define ALARM_LOWER_REG		0x0c
+#define ALARM_UPPER_REG		0x10
+#define COMPARE_LOWER_REG	0x14
+#define COMPARE_UPPER_REG	0x18
+#define DATETIME_LOWER_REG	0x20
+#define DATETIME_UPPER_REG	0x24
+
+#define CONTROL_RUNNING_BIT	BIT(0)
+#define CONTROL_START_BIT	BIT(0)
+#define CONTROL_STOP_BIT	BIT(1)
+#define CONTROL_ALARM_ON_BIT	BIT(2)
+#define CONTROL_ALARM_OFF_BIT	BIT(3)
+#define CONTROL_RESET_BIT	BIT(4)
+#define CONTROL_UPLOAD_BIT	BIT(5)
+#define CONTROL_DOWNLOAD_BIT	BIT(6)
+#define CONTROL_MATCH_BIT	BIT(7)
+#define CONTROL_WAKEUP_CLR_BIT	BIT(8)
+#define CONTROL_WAKEUP_SET_BIT	BIT(9)
+#define CONTROL_UPDATED_BIT	BIT(10)
+
+#define MODE_CLOCK_CALENDAR	BIT(0)
+#define MODE_WAKE_EN		BIT(1)
+#define MODE_WAKE_RESET		BIT(2)
+#define MODE_WAKE_CONTINUE	BIT(3)
+
+#define MAX_PRESCALER_COUNT	GENMASK(25, 0)
+#define DATETIME_UPPER_MASK	GENMASK(29, 0)
+#define ALARM_UPPER_MASK	GENMASK(10, 0)
+
+#define UPLOAD_TIMEOUT_US	50
+
+struct mpfs_rtc_dev {
+	struct rtc_device *rtc;
+	void __iomem *base;
+};
+
+static void mpfs_rtc_start(struct mpfs_rtc_dev *rtcdev)
+{
+	u32 ctrl;
+
+	ctrl = readl(rtcdev->base + CONTROL_REG);
+	ctrl &= ~CONTROL_STOP_BIT;
+	ctrl |= CONTROL_START_BIT;
+	writel(ctrl, rtcdev->base + CONTROL_REG);
+}
+
+static void mpfs_rtc_clear_irq(struct mpfs_rtc_dev *rtcdev)
+{
+	u32 val = readl(rtcdev->base + CONTROL_REG);
+
+	val &= ~(CONTROL_ALARM_ON_BIT | CONTROL_STOP_BIT);
+	val |= CONTROL_ALARM_OFF_BIT;
+	writel(val, rtcdev->base + CONTROL_REG);
+	/*
+	 * Ensure that the posted write to the CONTROL_REG register completed before
+	 * returning from this function. Not doing this may result in the interrupt
+	 * only being cleared some time after this function returns.
+	 */
+	(void)readl(rtcdev->base + CONTROL_REG);
+}
+
+static int mpfs_rtc_readtime(struct device *dev, struct rtc_time *tm)
+{
+	struct mpfs_rtc_dev *rtcdev = dev_get_drvdata(dev);
+	u64 time;
+
+	time = readl(rtcdev->base + DATETIME_LOWER_REG);
+	time |= ((u64)readl(rtcdev->base + DATETIME_UPPER_REG) & DATETIME_UPPER_MASK) << 32;
+	rtc_time64_to_tm(time, tm);
+
+	return 0;
+}
+
+static int mpfs_rtc_settime(struct device *dev, struct rtc_time *tm)
+{
+	struct mpfs_rtc_dev *rtcdev = dev_get_drvdata(dev);
+	u32 ctrl, prog;
+	u64 time;
+	int ret;
+
+	time = rtc_tm_to_time64(tm);
+
+	writel((u32)time, rtcdev->base + DATETIME_LOWER_REG);
+	writel((u32)(time >> 32) & DATETIME_UPPER_MASK, rtcdev->base + DATETIME_UPPER_REG);
+
+	ctrl = readl(rtcdev->base + CONTROL_REG);
+	ctrl &= ~CONTROL_STOP_BIT;
+	ctrl |= CONTROL_UPLOAD_BIT;
+	writel(ctrl, rtcdev->base + CONTROL_REG);
+
+	ret = read_poll_timeout(readl, prog, prog & CONTROL_UPLOAD_BIT, 0, UPLOAD_TIMEOUT_US,
+				false, rtcdev->base + CONTROL_REG);
+	if (ret) {
+		dev_err(dev, "timed out uploading time to rtc");
+		return ret;
+	}
+	mpfs_rtc_start(rtcdev);
+
+	return 0;
+}
+
+static int mpfs_rtc_readalarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct mpfs_rtc_dev *rtcdev = dev_get_drvdata(dev);
+	u32 mode = readl(rtcdev->base + MODE_REG);
+	u64 time;
+
+	alrm->enabled = mode & MODE_WAKE_EN;
+
+	time = (u64)readl(rtcdev->base + ALARM_LOWER_REG) << 32;
+	time |= (readl(rtcdev->base + ALARM_UPPER_REG) & ALARM_UPPER_MASK);
+	rtc_time64_to_tm(time, &alrm->time);
+
+	return 0;
+}
+
+static int mpfs_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct mpfs_rtc_dev *rtcdev = dev_get_drvdata(dev);
+	u32 mode, ctrl;
+	u64 time;
+
+	/* Disable the alarm before updating */
+	ctrl = readl(rtcdev->base + CONTROL_REG);
+	ctrl |= CONTROL_ALARM_OFF_BIT;
+	writel(ctrl, rtcdev->base + CONTROL_REG);
+
+	time = rtc_tm_to_time64(&alrm->time);
+
+	writel((u32)time, rtcdev->base + ALARM_LOWER_REG);
+	writel((u32)(time >> 32) & ALARM_UPPER_MASK, rtcdev->base + ALARM_UPPER_REG);
+
+	/* Bypass compare register in alarm mode */
+	writel(GENMASK(31, 0), rtcdev->base + COMPARE_LOWER_REG);
+	writel(GENMASK(29, 0), rtcdev->base + COMPARE_UPPER_REG);
+
+	/* Configure the RTC to enable the alarm. */
+	ctrl = readl(rtcdev->base + CONTROL_REG);
+	mode = readl(rtcdev->base + MODE_REG);
+	if (alrm->enabled) {
+		mode = MODE_WAKE_EN | MODE_WAKE_CONTINUE;
+		/* Enable the alarm */
+		ctrl &= ~CONTROL_ALARM_OFF_BIT;
+		ctrl |= CONTROL_ALARM_ON_BIT;
+	}
+	ctrl &= ~CONTROL_STOP_BIT;
+	ctrl |= CONTROL_START_BIT;
+	writel(ctrl, rtcdev->base + CONTROL_REG);
+	writel(mode, rtcdev->base + MODE_REG);
+
+	return 0;
+}
+
+static int mpfs_rtc_alarm_irq_enable(struct device *dev, unsigned int enabled)
+{
+	struct mpfs_rtc_dev *rtcdev = dev_get_drvdata(dev);
+	u32 ctrl;
+
+	ctrl = readl(rtcdev->base + CONTROL_REG);
+	ctrl &= ~(CONTROL_ALARM_ON_BIT | CONTROL_ALARM_OFF_BIT | CONTROL_STOP_BIT);
+
+	if (enabled)
+		ctrl |= CONTROL_ALARM_ON_BIT;
+	else
+		ctrl |= CONTROL_ALARM_OFF_BIT;
+
+	writel(ctrl, rtcdev->base + CONTROL_REG);
+
+	return 0;
+}
+
+static inline struct clk *mpfs_rtc_init_clk(struct device *dev)
+{
+	struct clk *clk;
+	int ret;
+
+	clk = devm_clk_get(dev, "rtc");
+	if (IS_ERR(clk))
+		return clk;
+
+	ret = clk_prepare_enable(clk);
+	if (ret)
+		return ERR_PTR(ret);
+
+	devm_add_action_or_reset(dev, (void (*) (void *))clk_disable_unprepare, clk);
+	return clk;
+}
+
+static irqreturn_t mpfs_rtc_wakeup_irq_handler(int irq, void *dev)
+{
+	struct mpfs_rtc_dev *rtcdev = dev;
+	unsigned long pending;
+
+	pending = readl(rtcdev->base + CONTROL_REG);
+	pending &= CONTROL_ALARM_ON_BIT;
+	mpfs_rtc_clear_irq(rtcdev);
+
+	rtc_update_irq(rtcdev->rtc, 1, RTC_IRQF | RTC_AF);
+
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops mpfs_rtc_ops = {
+	.read_time		= mpfs_rtc_readtime,
+	.set_time		= mpfs_rtc_settime,
+	.read_alarm		= mpfs_rtc_readalarm,
+	.set_alarm		= mpfs_rtc_setalarm,
+	.alarm_irq_enable	= mpfs_rtc_alarm_irq_enable,
+};
+
+static int mpfs_rtc_probe(struct platform_device *pdev)
+{
+	struct mpfs_rtc_dev *rtcdev;
+	struct clk *clk;
+	u32 prescaler;
+	int wakeup_irq, ret;
+
+	rtcdev = devm_kzalloc(&pdev->dev, sizeof(struct mpfs_rtc_dev), GFP_KERNEL);
+	if (!rtcdev)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, rtcdev);
+
+	rtcdev->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtcdev->rtc))
+		return PTR_ERR(rtcdev->rtc);
+
+	rtcdev->rtc->ops = &mpfs_rtc_ops;
+
+	/* range is capped by alarm max, lower reg is 31:0 & upper is 10:0 */
+	rtcdev->rtc->range_max = GENMASK_ULL(42, 0);
+
+	clk = mpfs_rtc_init_clk(&pdev->dev);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	rtcdev->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(rtcdev->base)) {
+		dev_dbg(&pdev->dev, "invalid ioremap resources\n");
+		return PTR_ERR(rtcdev->base);
+	}
+
+	wakeup_irq = platform_get_irq(pdev, 0);
+	if (wakeup_irq <= 0) {
+		dev_dbg(&pdev->dev, "could not get wakeup irq\n");
+		return wakeup_irq;
+	}
+	ret = devm_request_irq(&pdev->dev, wakeup_irq, mpfs_rtc_wakeup_irq_handler, 0,
+			       dev_name(&pdev->dev), rtcdev);
+	if (ret) {
+		dev_dbg(&pdev->dev, "could not request wakeup irq\n");
+		return ret;
+	}
+
+	/* prescaler hardware adds 1 to reg value */
+	prescaler = clk_get_rate(devm_clk_get(&pdev->dev, "rtcref")) - 1;
+
+	if (prescaler > MAX_PRESCALER_COUNT) {
+		dev_dbg(&pdev->dev, "invalid prescaler %d\n", prescaler);
+		return -EINVAL;
+	}
+
+	writel(prescaler, rtcdev->base + PRESCALER_REG);
+	dev_info(&pdev->dev, "prescaler set to: 0x%X \r\n", prescaler);
+
+	device_init_wakeup(&pdev->dev, true);
+	ret = dev_pm_set_wake_irq(&pdev->dev, wakeup_irq);
+	if (ret)
+		dev_err(&pdev->dev, "failed to enable irq wake\n");
+
+	return devm_rtc_register_device(rtcdev->rtc);
+}
+
+static int mpfs_rtc_remove(struct platform_device *pdev)
+{
+	dev_pm_clear_wake_irq(&pdev->dev);
+
+	return 0;
+}
+
+static const struct of_device_id mpfs_rtc_of_match[] = {
+	{ .compatible = "microchip,mpfs-rtc" },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, mpfs_rtc_of_match);
+
+static struct platform_driver mpfs_rtc_driver = {
+	.probe = mpfs_rtc_probe,
+	.remove = mpfs_rtc_remove,
+	.driver	= {
+		.name = "mpfs_rtc",
+		.of_match_table = mpfs_rtc_of_match,
+	},
+};
+
+module_platform_driver(mpfs_rtc_driver);
+
+MODULE_DESCRIPTION("Real time clock for Microchip Polarfire SoC");
+MODULE_AUTHOR("Daire McNamara <daire.mcnamara@microchip.com>");
+MODULE_AUTHOR("Conor Dooley <conor.dooley@microchip.com>");
+MODULE_LICENSE("GPL");