rtc: bbnsm: Add the bbnsm rtc support

The BBNSM module includes a real time counter with alarm.
Add a RTC driver for this function.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/20230215024117.3357341-3-ping.bai@nxp.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

drivers/rtc/Kconfig

@@ -1786,6 +1786,18 @@ config RTC_DRV_SNVS
 	   This driver can also be built as a module, if so, the module
 	   will be called "rtc-snvs".
 
+config RTC_DRV_BBNSM
+	tristate "NXP BBNSM RTC support"
+	select REGMAP_MMIO
+	depends on ARCH_MXC || COMPILE_TEST
+	depends on HAS_IOMEM
+	depends on OF
+	help
+	   If you say yes here you get support for the NXP BBNSM RTC module.
+
+	   This driver can also be built as a module, if so, the module
+	   will be called "rtc-bbnsm".
+
 config RTC_DRV_IMX_SC
 	depends on IMX_SCU
 	depends on HAVE_ARM_SMCCC

drivers/rtc/Makefile

@@ -33,6 +33,7 @@ obj-$(CONFIG_RTC_DRV_ASPEED)	+= rtc-aspeed.o
 obj-$(CONFIG_RTC_DRV_AT91RM9200)+= rtc-at91rm9200.o
 obj-$(CONFIG_RTC_DRV_AT91SAM9)	+= rtc-at91sam9.o
 obj-$(CONFIG_RTC_DRV_AU1XXX)	+= rtc-au1xxx.o
+obj-$(CONFIG_RTC_DRV_BBNSM)	+= rtc-nxp-bbnsm.o
 obj-$(CONFIG_RTC_DRV_BD70528)	+= rtc-bd70528.o
 obj-$(CONFIG_RTC_DRV_BQ32K)	+= rtc-bq32k.o
 obj-$(CONFIG_RTC_DRV_BQ4802)	+= rtc-bq4802.o

drivers/rtc/rtc-nxp-bbnsm.c

@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Copyright 2022 NXP.
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm_wakeirq.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+
+#define BBNSM_CTRL	0x8
+#define BBNSM_INT_EN	0x10
+#define BBNSM_EVENTS	0x14
+#define BBNSM_RTC_LS	0x40
+#define BBNSM_RTC_MS	0x44
+#define BBNSM_TA	0x50
+
+#define RTC_EN		0x2
+#define RTC_EN_MSK	0x3
+#define TA_EN		(0x2 << 2)
+#define TA_DIS		(0x1 << 2)
+#define TA_EN_MSK	(0x3 << 2)
+#define RTC_INT_EN	0x2
+#define TA_INT_EN	(0x2 << 2)
+
+#define BBNSM_EVENT_TA	(0x2 << 2)
+
+#define CNTR_TO_SECS_SH	15
+
+struct bbnsm_rtc {
+	struct rtc_device *rtc;
+	struct regmap *regmap;
+	int irq;
+	struct clk *clk;
+};
+
+static u32 bbnsm_read_counter(struct bbnsm_rtc *bbnsm)
+{
+	u32 rtc_msb, rtc_lsb;
+	unsigned int timeout = 100;
+	u32 time;
+	u32 tmp = 0;
+
+	do {
+		time = tmp;
+		/* read the msb */
+		regmap_read(bbnsm->regmap, BBNSM_RTC_MS, &rtc_msb);
+		/* read the lsb */
+		regmap_read(bbnsm->regmap, BBNSM_RTC_LS, &rtc_lsb);
+		/* convert to seconds */
+		tmp = (rtc_msb << 17) | (rtc_lsb >> 15);
+	} while (tmp != time && --timeout);
+
+	return time;
+}
+
+static int bbnsm_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct bbnsm_rtc *bbnsm = dev_get_drvdata(dev);
+	unsigned long time;
+	u32 val;
+
+	regmap_read(bbnsm->regmap, BBNSM_CTRL, &val);
+	if ((val & RTC_EN_MSK) != RTC_EN)
+		return -EINVAL;
+
+	time = bbnsm_read_counter(bbnsm);
+	rtc_time64_to_tm(time, tm);
+
+	return 0;
+}
+
+static int bbnsm_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct bbnsm_rtc *bbnsm = dev_get_drvdata(dev);
+	unsigned long time = rtc_tm_to_time64(tm);
+
+	/* disable the RTC first */
+	regmap_update_bits(bbnsm->regmap, BBNSM_CTRL, RTC_EN_MSK, 0);
+
+	/* write the 32bit sec time to 47 bit timer counter, leaving 15 LSBs blank */
+	regmap_write(bbnsm->regmap, BBNSM_RTC_LS, time << CNTR_TO_SECS_SH);
+	regmap_write(bbnsm->regmap, BBNSM_RTC_MS, time >> (32 - CNTR_TO_SECS_SH));
+
+	/* Enable the RTC again */
+	regmap_update_bits(bbnsm->regmap, BBNSM_CTRL, RTC_EN_MSK, RTC_EN);
+
+	return 0;
+}
+
+static int bbnsm_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct bbnsm_rtc *bbnsm = dev_get_drvdata(dev);
+	u32 bbnsm_events, bbnsm_ta;
+
+	regmap_read(bbnsm->regmap, BBNSM_TA, &bbnsm_ta);
+	rtc_time64_to_tm(bbnsm_ta, &alrm->time);
+
+	regmap_read(bbnsm->regmap, BBNSM_EVENTS, &bbnsm_events);
+	alrm->pending = (bbnsm_events & BBNSM_EVENT_TA) ? 1 : 0;
+
+	return 0;
+}
+
+static int bbnsm_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)
+{
+	struct bbnsm_rtc *bbnsm = dev_get_drvdata(dev);
+
+	/* enable the alarm event */
+	regmap_update_bits(bbnsm->regmap, BBNSM_CTRL, TA_EN_MSK, enable ? TA_EN : TA_DIS);
+	/* enable the alarm interrupt */
+	regmap_update_bits(bbnsm->regmap, BBNSM_INT_EN, TA_EN_MSK, enable ? TA_EN : TA_DIS);
+
+	return 0;
+}
+
+static int bbnsm_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct bbnsm_rtc *bbnsm = dev_get_drvdata(dev);
+	unsigned long time = rtc_tm_to_time64(&alrm->time);
+
+	/* disable the alarm */
+	regmap_update_bits(bbnsm->regmap, BBNSM_CTRL, TA_EN, TA_EN);
+
+	/* write the seconds to TA */
+	regmap_write(bbnsm->regmap, BBNSM_TA, time);
+
+	return bbnsm_rtc_alarm_irq_enable(dev, alrm->enabled);
+}
+
+static const struct rtc_class_ops bbnsm_rtc_ops = {
+	.read_time = bbnsm_rtc_read_time,
+	.set_time = bbnsm_rtc_set_time,
+	.read_alarm = bbnsm_rtc_read_alarm,
+	.set_alarm = bbnsm_rtc_set_alarm,
+	.alarm_irq_enable = bbnsm_rtc_alarm_irq_enable,
+};
+
+static irqreturn_t bbnsm_rtc_irq_handler(int irq, void *dev_id)
+{
+	struct device *dev = dev_id;
+	struct bbnsm_rtc  *bbnsm = dev_get_drvdata(dev);
+	u32 val;
+
+	regmap_read(bbnsm->regmap, BBNSM_EVENTS, &val);
+	if (val & BBNSM_EVENT_TA) {
+		bbnsm_rtc_alarm_irq_enable(dev, false);
+		/* clear the alarm event */
+		regmap_write_bits(bbnsm->regmap, BBNSM_EVENTS, TA_EN_MSK, BBNSM_EVENT_TA);
+		rtc_update_irq(bbnsm->rtc, 1, RTC_AF | RTC_IRQF);
+
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static int bbnsm_rtc_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct bbnsm_rtc *bbnsm;
+	int ret;
+
+	bbnsm = devm_kzalloc(&pdev->dev, sizeof(*bbnsm), GFP_KERNEL);
+	if (!bbnsm)
+		return -ENOMEM;
+
+	bbnsm->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(bbnsm->rtc))
+		return PTR_ERR(bbnsm->rtc);
+
+	bbnsm->regmap = syscon_node_to_regmap(np->parent);
+	if (IS_ERR(bbnsm->regmap)) {
+		dev_dbg(&pdev->dev, "bbnsm get regmap failed\n");
+		return PTR_ERR(bbnsm->regmap);
+	}
+
+	bbnsm->irq = platform_get_irq(pdev, 0);
+	if (bbnsm->irq < 0)
+		return bbnsm->irq;
+
+	platform_set_drvdata(pdev, bbnsm);
+
+	/* clear all the pending events */
+	regmap_write(bbnsm->regmap, BBNSM_EVENTS, 0x7A);
+
+	device_init_wakeup(&pdev->dev, true);
+	dev_pm_set_wake_irq(&pdev->dev, bbnsm->irq);
+
+	ret = devm_request_irq(&pdev->dev, bbnsm->irq, bbnsm_rtc_irq_handler,
+			       IRQF_SHARED, "rtc alarm", &pdev->dev);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to request irq %d: %d\n",
+			bbnsm->irq, ret);
+		return ret;
+	}
+
+	bbnsm->rtc->ops = &bbnsm_rtc_ops;
+	bbnsm->rtc->range_max = U32_MAX;
+
+	return devm_rtc_register_device(bbnsm->rtc);
+}
+
+static const struct of_device_id bbnsm_dt_ids[] = {
+	{ .compatible = "nxp,imx93-bbnsm-rtc" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, bbnsm_dt_ids);
+
+static struct platform_driver bbnsm_rtc_driver = {
+	.driver = {
+		.name = "bbnsm_rtc",
+		.of_match_table = bbnsm_dt_ids,
+	},
+	.probe = bbnsm_rtc_probe,
+};
+module_platform_driver(bbnsm_rtc_driver);
+
+MODULE_AUTHOR("Jacky Bai <ping.bai@nxp.com>");
+MODULE_DESCRIPTION("NXP BBNSM RTC Driver");
+MODULE_LICENSE("GPL");