rtc: add rtc-lpc24xx driver

Add driver for the RTC found on NXP LPC178x/18xx/408x/43xx devices.
The RTC provides calendar and clock functionality together with
alarm interrupt support.

Signed-off-by: Joachim Eastwood <[e-mail]>
Signed-off-by: Alexandre Belloni <[e-mail]>

drivers/rtc/Kconfig

···
 	  This driver can also be buillt as a module. If so, the module
 	  will be called rtc-jz4740.
 
+config RTC_DRV_LPC24XX
+	tristate "NXP RTC for LPC178x/18xx/408x/43xx"
+	depends on ARCH_LPC18XX || COMPILE_TEST
+	depends on OF && HAS_IOMEM
+	help
+	  This enables support for the NXP RTC found which can be found on
+	  NXP LPC178x/18xx/408x/43xx devices.
+
+	  If you have one of the devices above enable this driver to use
+	  the hardware RTC. This driver can also be buillt as a module. If
+	  so, the module will be called rtc-lpc24xx.
+
 config RTC_DRV_LPC32XX
 	depends on ARCH_LPC32XX
 	tristate "NXP LPC32XX RTC"

drivers/rtc/Makefile

···
 obj-$(CONFIG_RTC_DRV_ISL1208)	+= rtc-isl1208.o
 obj-$(CONFIG_RTC_DRV_JZ4740)	+= rtc-jz4740.o
 obj-$(CONFIG_RTC_DRV_LP8788)	+= rtc-lp8788.o
+obj-$(CONFIG_RTC_DRV_LPC24XX)	+= rtc-lpc24xx.o
 obj-$(CONFIG_RTC_DRV_LPC32XX)	+= rtc-lpc32xx.o
 obj-$(CONFIG_RTC_DRV_LOONGSON1)	+= rtc-ls1x.o
 obj-$(CONFIG_RTC_DRV_M41T80)	+= rtc-m41t80.o

drivers/rtc/rtc-lpc24xx.c

···
+/*
+ * RTC driver for NXP LPC178x/18xx/43xx Real-Time Clock (RTC)
+ *
+ * Copyright (C) 2011 NXP Semiconductors
+ * Copyright (C) 2015 Joachim Eastwood <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+
+/* LPC24xx RTC register offsets and bits */
+#define LPC24XX_ILR		0x00
+#define  LPC24XX_RTCCIF		BIT(0)
+#define  LPC24XX_RTCALF		BIT(1)
+#define LPC24XX_CTC		0x04
+#define LPC24XX_CCR		0x08
+#define  LPC24XX_CLKEN		BIT(0)
+#define  LPC178X_CCALEN		BIT(4)
+#define LPC24XX_CIIR		0x0c
+#define LPC24XX_AMR		0x10
+#define  LPC24XX_ALARM_DISABLE	0xff
+#define LPC24XX_CTIME0		0x14
+#define LPC24XX_CTIME1		0x18
+#define LPC24XX_CTIME2		0x1c
+#define LPC24XX_SEC		0x20
+#define LPC24XX_MIN		0x24
+#define LPC24XX_HOUR		0x28
+#define LPC24XX_DOM		0x2c
+#define LPC24XX_DOW		0x30
+#define LPC24XX_DOY		0x34
+#define LPC24XX_MONTH		0x38
+#define LPC24XX_YEAR		0x3c
+#define LPC24XX_ALSEC		0x60
+#define LPC24XX_ALMIN		0x64
+#define LPC24XX_ALHOUR		0x68
+#define LPC24XX_ALDOM		0x6c
+#define LPC24XX_ALDOW		0x70
+#define LPC24XX_ALDOY		0x74
+#define LPC24XX_ALMON		0x78
+#define LPC24XX_ALYEAR		0x7c
+
+/* Macros to read fields in consolidated time (CT) registers */
+#define CT0_SECS(x)		(((x) >> 0)  & 0x3f)
+#define CT0_MINS(x)		(((x) >> 8)  & 0x3f)
+#define CT0_HOURS(x)		(((x) >> 16) & 0x1f)
+#define CT0_DOW(x)		(((x) >> 24) & 0x07)
+#define CT1_DOM(x)		(((x) >> 0)  & 0x1f)
+#define CT1_MONTH(x)		(((x) >> 8)  & 0x0f)
+#define CT1_YEAR(x)		(((x) >> 16) & 0xfff)
+#define CT2_DOY(x)		(((x) >> 0)  & 0xfff)
+
+#define rtc_readl(dev, reg)		readl((dev)->rtc_base + (reg))
+#define rtc_writel(dev, reg, val)	writel((val), (dev)->rtc_base + (reg))
+
+struct lpc24xx_rtc {
+	void __iomem *rtc_base;
+	struct rtc_device *rtc;
+	struct clk *clk_rtc;
+	struct clk *clk_reg;
+};
+
+static int lpc24xx_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct lpc24xx_rtc *rtc = dev_get_drvdata(dev);
+
+	/* Disable RTC during update */
+	rtc_writel(rtc, LPC24XX_CCR, LPC178X_CCALEN);
+
+	rtc_writel(rtc, LPC24XX_SEC,	tm->tm_sec);
+	rtc_writel(rtc, LPC24XX_MIN,	tm->tm_min);
+	rtc_writel(rtc, LPC24XX_HOUR,	tm->tm_hour);
+	rtc_writel(rtc, LPC24XX_DOW,	tm->tm_wday);
+	rtc_writel(rtc, LPC24XX_DOM,	tm->tm_mday);
+	rtc_writel(rtc, LPC24XX_DOY,	tm->tm_yday);
+	rtc_writel(rtc, LPC24XX_MONTH,	tm->tm_mon);
+	rtc_writel(rtc, LPC24XX_YEAR,	tm->tm_year);
+
+	rtc_writel(rtc, LPC24XX_CCR, LPC24XX_CLKEN | LPC178X_CCALEN);
+
+	return 0;
+}
+
+static int lpc24xx_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct lpc24xx_rtc *rtc = dev_get_drvdata(dev);
+	u32 ct0, ct1, ct2;
+
+	ct0 = rtc_readl(rtc, LPC24XX_CTIME0);
+	ct1 = rtc_readl(rtc, LPC24XX_CTIME1);
+	ct2 = rtc_readl(rtc, LPC24XX_CTIME2);
+
+	tm->tm_sec  = CT0_SECS(ct0);
+	tm->tm_min  = CT0_MINS(ct0);
+	tm->tm_hour = CT0_HOURS(ct0);
+	tm->tm_wday = CT0_DOW(ct0);
+	tm->tm_mon  = CT1_MONTH(ct1);
+	tm->tm_mday = CT1_DOM(ct1);
+	tm->tm_year = CT1_YEAR(ct1);
+	tm->tm_yday = CT2_DOY(ct2);
+
+	return rtc_valid_tm(tm);
+}
+
+static int lpc24xx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
+{
+	struct lpc24xx_rtc *rtc = dev_get_drvdata(dev);
+	struct rtc_time *tm = &wkalrm->time;
+
+	tm->tm_sec  = rtc_readl(rtc, LPC24XX_ALSEC);
+	tm->tm_min  = rtc_readl(rtc, LPC24XX_ALMIN);
+	tm->tm_hour = rtc_readl(rtc, LPC24XX_ALHOUR);
+	tm->tm_mday = rtc_readl(rtc, LPC24XX_ALDOM);
+	tm->tm_wday = rtc_readl(rtc, LPC24XX_ALDOW);
+	tm->tm_yday = rtc_readl(rtc, LPC24XX_ALDOY);
+	tm->tm_mon  = rtc_readl(rtc, LPC24XX_ALMON);
+	tm->tm_year = rtc_readl(rtc, LPC24XX_ALYEAR);
+
+	wkalrm->enabled = rtc_readl(rtc, LPC24XX_AMR) == 0;
+	wkalrm->pending = !!(rtc_readl(rtc, LPC24XX_ILR) & LPC24XX_RTCCIF);
+
+	return rtc_valid_tm(&wkalrm->time);
+}
+
+static int lpc24xx_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *wkalrm)
+{
+	struct lpc24xx_rtc *rtc = dev_get_drvdata(dev);
+	struct rtc_time *tm = &wkalrm->time;
+
+	/* Disable alarm irq during update */
+	rtc_writel(rtc, LPC24XX_AMR, LPC24XX_ALARM_DISABLE);
+
+	rtc_writel(rtc, LPC24XX_ALSEC,  tm->tm_sec);
+	rtc_writel(rtc, LPC24XX_ALMIN,  tm->tm_min);
+	rtc_writel(rtc, LPC24XX_ALHOUR, tm->tm_hour);
+	rtc_writel(rtc, LPC24XX_ALDOM,  tm->tm_mday);
+	rtc_writel(rtc, LPC24XX_ALDOW,  tm->tm_wday);
+	rtc_writel(rtc, LPC24XX_ALDOY,  tm->tm_yday);
+	rtc_writel(rtc, LPC24XX_ALMON,  tm->tm_mon);
+	rtc_writel(rtc, LPC24XX_ALYEAR, tm->tm_year);
+
+	if (wkalrm->enabled)
+		rtc_writel(rtc, LPC24XX_AMR, 0);
+
+	return 0;
+}
+
+static int lpc24xx_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)
+{
+	struct lpc24xx_rtc *rtc = dev_get_drvdata(dev);
+
+	if (enable)
+		rtc_writel(rtc, LPC24XX_AMR, 0);
+	else
+		rtc_writel(rtc, LPC24XX_AMR, LPC24XX_ALARM_DISABLE);
+
+	return 0;
+}
+
+static irqreturn_t lpc24xx_rtc_interrupt(int irq, void *data)
+{
+	unsigned long events = RTC_IRQF;
+	struct lpc24xx_rtc *rtc = data;
+	u32 rtc_iir;
+
+	/* Check interrupt cause */
+	rtc_iir = rtc_readl(rtc, LPC24XX_ILR);
+	if (rtc_iir & LPC24XX_RTCALF) {
+		events |= RTC_AF;
+		rtc_writel(rtc, LPC24XX_AMR, LPC24XX_ALARM_DISABLE);
+	}
+
+	/* Clear interrupt status and report event */
+	rtc_writel(rtc, LPC24XX_ILR, rtc_iir);
+	rtc_update_irq(rtc->rtc, 1, events);
+
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops lpc24xx_rtc_ops = {
+	.read_time		= lpc24xx_rtc_read_time,
+	.set_time		= lpc24xx_rtc_set_time,
+	.read_alarm		= lpc24xx_rtc_read_alarm,
+	.set_alarm		= lpc24xx_rtc_set_alarm,
+	.alarm_irq_enable	= lpc24xx_rtc_alarm_irq_enable,
+};
+
+static int lpc24xx_rtc_probe(struct platform_device *pdev)
+{
+	struct lpc24xx_rtc *rtc;
+	struct resource *res;
+	int irq, ret;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	rtc->rtc_base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(rtc->rtc_base))
+		return PTR_ERR(rtc->rtc_base);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0) {
+		dev_warn(&pdev->dev, "can't get interrupt resource\n");
+		return irq;
+	}
+
+	rtc->clk_rtc = devm_clk_get(&pdev->dev, "rtc");
+	if (IS_ERR(rtc->clk_rtc)) {
+		dev_err(&pdev->dev, "error getting rtc clock\n");
+		return PTR_ERR(rtc->clk_rtc);
+	}
+
+	rtc->clk_reg = devm_clk_get(&pdev->dev, "reg");
+	if (IS_ERR(rtc->clk_reg)) {
+		dev_err(&pdev->dev, "error getting reg clock\n");
+		return PTR_ERR(rtc->clk_reg);
+	}
+
+	ret = clk_prepare_enable(rtc->clk_rtc);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to enable rtc clock\n");
+		return ret;
+	}
+
+	ret = clk_prepare_enable(rtc->clk_reg);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to enable reg clock\n");
+		goto disable_rtc_clk;
+	}
+
+	platform_set_drvdata(pdev, rtc);
+
+	/* Clear any pending interrupts */
+	rtc_writel(rtc, LPC24XX_ILR, LPC24XX_RTCCIF | LPC24XX_RTCALF);
+
+	/* Enable RTC count */
+	rtc_writel(rtc, LPC24XX_CCR, LPC24XX_CLKEN | LPC178X_CCALEN);
+
+	ret = devm_request_irq(&pdev->dev, irq, lpc24xx_rtc_interrupt, 0,
+			       pdev->name, rtc);
+	if (ret < 0) {
+		dev_warn(&pdev->dev, "can't request interrupt\n");
+		goto disable_clks;
+	}
+
+	rtc->rtc = devm_rtc_device_register(&pdev->dev, "lpc24xx-rtc",
+					    &lpc24xx_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc->rtc)) {
+		dev_err(&pdev->dev, "can't register rtc device\n");
+		ret = PTR_ERR(rtc->rtc);
+		goto disable_clks;
+	}
+
+	return 0;
+
+disable_clks:
+	clk_disable_unprepare(rtc->clk_reg);
+disable_rtc_clk:
+	clk_disable_unprepare(rtc->clk_rtc);
+	return ret;
+}
+
+static int lpc24xx_rtc_remove(struct platform_device *pdev)
+{
+	struct lpc24xx_rtc *rtc = platform_get_drvdata(pdev);
+
+	/* Ensure all interrupt sources are masked */
+	rtc_writel(rtc, LPC24XX_AMR, LPC24XX_ALARM_DISABLE);
+	rtc_writel(rtc, LPC24XX_CIIR, 0);
+
+	rtc_writel(rtc, LPC24XX_CCR, LPC178X_CCALEN);
+
+	clk_disable_unprepare(rtc->clk_rtc);
+	clk_disable_unprepare(rtc->clk_reg);
+
+	return 0;
+}
+
+static const struct of_device_id lpc24xx_rtc_match[] = {
+	{ .compatible = "nxp,lpc1788-rtc" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, lpc24xx_rtc_match);
+
+static struct platform_driver lpc24xx_rtc_driver = {
+	.probe	= lpc24xx_rtc_probe,
+	.remove	= lpc24xx_rtc_remove,
+	.driver	= {
+		.name = "lpc24xx-rtc",
+		.of_match_table	= lpc24xx_rtc_match,
+	},
+};
+module_platform_driver(lpc24xx_rtc_driver);
+
+MODULE_AUTHOR("Kevin Wells <[e-mail]>");
+MODULE_DESCRIPTION("RTC driver for the LPC178x/18xx/408x/43xx SoCs");
+MODULE_LICENSE("GPL");