drivers/rtc/rtc-sirfsoc.c: add rtc drivers for CSR SiRFprimaII and SiRFatlasVI

On CSR SiRFprimaII/atlasVI, there is a programmable 16-bit divider
(RTC_DIV) that divides the input 32.768KHz clock to the frequency that
users need (E.g.  1 Hz).  The divided real-time clock will be used to
drive a 32-bit counter (RTC_COUNTER) that provides users with the actual
time.

In each cycle of the divided real-time clock, there is a Hertz interrupt
generated to the RISC.  Users can also configure an alarm (RTC_ALARM).
When RTC_COUNTER matches the alarm, there will be an alarm interrupt
generated to the RISC.

The system RTC can generate an alarm wake-up signal to notify the power
controller to wake up from power saving mode.

Signed-off-by: Xianglong Du <Xianglong.Du@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Cc: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm/boot/dts/atlas6.dtsi

@@ -613,7 +613,7 @@
 		};
 
 		rtc-iobg {
-			compatible = "sirf,prima2-rtciobg", "sirf-prima2-rtciobg-bus";
+			compatible = "sirf,prima2-rtciobg", "sirf-prima2-rtciobg-bus", "simple-bus";
 			#address-cells = <1>;
 			#size-cells = <1>;
 			reg = <0x80030000 0x10000>;

arch/arm/boot/dts/prima2.dtsi

@@ -610,7 +610,7 @@
 		};
 
 		rtc-iobg {
-			compatible = "sirf,prima2-rtciobg", "sirf-prima2-rtciobg-bus";
+			compatible = "sirf,prima2-rtciobg", "sirf-prima2-rtciobg-bus", "simple-bus";
 			#address-cells = <1>;
 			#size-cells = <1>;
 			reg = <0x80030000 0x10000>;

drivers/rtc/Kconfig

@@ -1242,6 +1242,13 @@ 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_SIRFSOC
+	tristate "SiRFSOC RTC"
+	depends on ARCH_SIRF
+	help
+	  Say "yes" here to support the real time clock on SiRF SOC chips.
+	  This driver can also be built as a module called rtc-sirfsoc.
+
 comment "HID Sensor RTC drivers"
 
 config RTC_DRV_HID_SENSOR_TIME

drivers/rtc/Makefile

@@ -129,3 +129,4 @@ obj-$(CONFIG_RTC_DRV_VT8500)	+= rtc-vt8500.o
 obj-$(CONFIG_RTC_DRV_WM831X)	+= rtc-wm831x.o
 obj-$(CONFIG_RTC_DRV_WM8350)	+= rtc-wm8350.o
 obj-$(CONFIG_RTC_DRV_X1205)	+= rtc-x1205.o
+obj-$(CONFIG_RTC_DRV_SIRFSOC)	+= rtc-sirfsoc.o

drivers/rtc/rtc-sirfsoc.c

@@ -0,0 +1,475 @@
+/*
+ * SiRFSoC Real Time Clock interface for Linux
+ *
+ * Copyright (c) 2013 Cambridge Silicon Radio Limited, a CSR plc group company.
+ *
+ * Licensed under GPLv2 or later.
+ */
+
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/rtc.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/rtc/sirfsoc_rtciobrg.h>
+
+
+#define RTC_CN			0x00
+#define RTC_ALARM0		0x04
+#define RTC_ALARM1		0x18
+#define RTC_STATUS		0x08
+#define RTC_SW_VALUE            0x40
+#define SIRFSOC_RTC_AL1E	(1<<6)
+#define SIRFSOC_RTC_AL1		(1<<4)
+#define SIRFSOC_RTC_HZE		(1<<3)
+#define SIRFSOC_RTC_AL0E	(1<<2)
+#define SIRFSOC_RTC_HZ		(1<<1)
+#define SIRFSOC_RTC_AL0		(1<<0)
+#define RTC_DIV			0x0c
+#define RTC_DEEP_CTRL		0x14
+#define RTC_CLOCK_SWITCH	0x1c
+#define SIRFSOC_RTC_CLK		0x03	/* others are reserved */
+
+/* Refer to RTC DIV switch */
+#define RTC_HZ			16
+
+/* This macro is also defined in arch/arm/plat-sirfsoc/cpu.c */
+#define RTC_SHIFT		4
+
+#define INTR_SYSRTC_CN		0x48
+
+struct sirfsoc_rtc_drv {
+	struct rtc_device	*rtc;
+	u32			rtc_base;
+	u32			irq;
+	/* Overflow for every 8 years extra time */
+	u32			overflow_rtc;
+#ifdef CONFIG_PM
+	u32		saved_counter;
+	u32		saved_overflow_rtc;
+#endif
+};
+
+static int sirfsoc_rtc_read_alarm(struct device *dev,
+		struct rtc_wkalrm *alrm)
+{
+	unsigned long rtc_alarm, rtc_count;
+	struct sirfsoc_rtc_drv *rtcdrv;
+
+	rtcdrv = (struct sirfsoc_rtc_drv *)dev_get_drvdata(dev);
+
+	local_irq_disable();
+
+	rtc_count = sirfsoc_rtc_iobrg_readl(rtcdrv->rtc_base + RTC_CN);
+
+	rtc_alarm = sirfsoc_rtc_iobrg_readl(rtcdrv->rtc_base + RTC_ALARM0);
+	memset(alrm, 0, sizeof(struct rtc_wkalrm));
+
+	/*
+	 * assume alarm interval not beyond one round counter overflow_rtc:
+	 * 0->0xffffffff
+	 */
+	/* if alarm is in next overflow cycle */
+	if (rtc_count > rtc_alarm)
+		rtc_time_to_tm((rtcdrv->overflow_rtc + 1)
+				<< (BITS_PER_LONG - RTC_SHIFT)
+				| rtc_alarm >> RTC_SHIFT, &(alrm->time));
+	else
+		rtc_time_to_tm(rtcdrv->overflow_rtc
+				<< (BITS_PER_LONG - RTC_SHIFT)
+				| rtc_alarm >> RTC_SHIFT, &(alrm->time));
+	if (sirfsoc_rtc_iobrg_readl(
+			rtcdrv->rtc_base + RTC_STATUS) & SIRFSOC_RTC_AL0E)
+		alrm->enabled = 1;
+	local_irq_enable();
+
+	return 0;
+}
+
+static int sirfsoc_rtc_set_alarm(struct device *dev,
+		struct rtc_wkalrm *alrm)
+{
+	unsigned long rtc_status_reg, rtc_alarm;
+	struct sirfsoc_rtc_drv *rtcdrv;
+	rtcdrv = (struct sirfsoc_rtc_drv *)dev_get_drvdata(dev);
+
+	if (alrm->enabled) {
+		rtc_tm_to_time(&(alrm->time), &rtc_alarm);
+
+		local_irq_disable();
+
+		rtc_status_reg = sirfsoc_rtc_iobrg_readl(
+				rtcdrv->rtc_base + RTC_STATUS);
+		if (rtc_status_reg & SIRFSOC_RTC_AL0E) {
+			/*
+			 * An ongoing alarm in progress - ingore it and not
+			 * to return EBUSY
+			 */
+			dev_info(dev, "An old alarm was set, will be replaced by a new one\n");
+		}
+
+		sirfsoc_rtc_iobrg_writel(
+			rtc_alarm << RTC_SHIFT, rtcdrv->rtc_base + RTC_ALARM0);
+		rtc_status_reg &= ~0x07; /* mask out the lower status bits */
+		/*
+		 * This bit RTC_AL sets it as a wake-up source for Sleep Mode
+		 * Writing 1 into this bit will clear it
+		 */
+		rtc_status_reg |= SIRFSOC_RTC_AL0;
+		/* enable the RTC alarm interrupt */
+		rtc_status_reg |= SIRFSOC_RTC_AL0E;
+		sirfsoc_rtc_iobrg_writel(
+			rtc_status_reg, rtcdrv->rtc_base + RTC_STATUS);
+		local_irq_enable();
+	} else {
+		/*
+		 * if this function was called with enabled=0
+		 * then it could mean that the application is
+		 * trying to cancel an ongoing alarm
+		 */
+		local_irq_disable();
+
+		rtc_status_reg = sirfsoc_rtc_iobrg_readl(
+				rtcdrv->rtc_base + RTC_STATUS);
+		if (rtc_status_reg & SIRFSOC_RTC_AL0E) {
+			/* clear the RTC status register's alarm bit */
+			rtc_status_reg &= ~0x07;
+			/* write 1 into SIRFSOC_RTC_AL0 to force a clear */
+			rtc_status_reg |= (SIRFSOC_RTC_AL0);
+			/* Clear the Alarm enable bit */
+			rtc_status_reg &= ~(SIRFSOC_RTC_AL0E);
+
+			sirfsoc_rtc_iobrg_writel(rtc_status_reg,
+					rtcdrv->rtc_base + RTC_STATUS);
+		}
+
+		local_irq_enable();
+	}
+
+	return 0;
+}
+
+static int sirfsoc_rtc_read_time(struct device *dev,
+		struct rtc_time *tm)
+{
+	unsigned long tmp_rtc = 0;
+	struct sirfsoc_rtc_drv *rtcdrv;
+	rtcdrv = (struct sirfsoc_rtc_drv *)dev_get_drvdata(dev);
+	/*
+	 * This patch is taken from WinCE - Need to validate this for
+	 * correctness. To work around sirfsoc RTC counter double sync logic
+	 * fail, read several times to make sure get stable value.
+	 */
+	do {
+		tmp_rtc = sirfsoc_rtc_iobrg_readl(rtcdrv->rtc_base + RTC_CN);
+		cpu_relax();
+	} while (tmp_rtc != sirfsoc_rtc_iobrg_readl(rtcdrv->rtc_base + RTC_CN));
+
+	rtc_time_to_tm(rtcdrv->overflow_rtc << (BITS_PER_LONG - RTC_SHIFT) |
+					tmp_rtc >> RTC_SHIFT, tm);
+	return 0;
+}
+
+static int sirfsoc_rtc_set_time(struct device *dev,
+		struct rtc_time *tm)
+{
+	unsigned long rtc_time;
+	struct sirfsoc_rtc_drv *rtcdrv;
+	rtcdrv = (struct sirfsoc_rtc_drv *)dev_get_drvdata(dev);
+
+	rtc_tm_to_time(tm, &rtc_time);
+
+	rtcdrv->overflow_rtc = rtc_time >> (BITS_PER_LONG - RTC_SHIFT);
+
+	sirfsoc_rtc_iobrg_writel(rtcdrv->overflow_rtc,
+			rtcdrv->rtc_base + RTC_SW_VALUE);
+	sirfsoc_rtc_iobrg_writel(
+			rtc_time << RTC_SHIFT, rtcdrv->rtc_base + RTC_CN);
+
+	return 0;
+}
+
+static int sirfsoc_rtc_ioctl(struct device *dev, unsigned int cmd,
+		unsigned long arg)
+{
+	switch (cmd) {
+	case RTC_PIE_ON:
+	case RTC_PIE_OFF:
+	case RTC_UIE_ON:
+	case RTC_UIE_OFF:
+	case RTC_AIE_ON:
+	case RTC_AIE_OFF:
+		return 0;
+
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+
+static const struct rtc_class_ops sirfsoc_rtc_ops = {
+	.read_time = sirfsoc_rtc_read_time,
+	.set_time = sirfsoc_rtc_set_time,
+	.read_alarm = sirfsoc_rtc_read_alarm,
+	.set_alarm = sirfsoc_rtc_set_alarm,
+	.ioctl = sirfsoc_rtc_ioctl
+};
+
+static irqreturn_t sirfsoc_rtc_irq_handler(int irq, void *pdata)
+{
+	struct sirfsoc_rtc_drv *rtcdrv = pdata;
+	unsigned long rtc_status_reg = 0x0;
+	unsigned long events = 0x0;
+
+	rtc_status_reg = sirfsoc_rtc_iobrg_readl(rtcdrv->rtc_base + RTC_STATUS);
+	/* this bit will be set ONLY if an alarm was active
+	 * and it expired NOW
+	 * So this is being used as an ASSERT
+	 */
+	if (rtc_status_reg & SIRFSOC_RTC_AL0) {
+		/*
+		 * clear the RTC status register's alarm bit
+		 * mask out the lower status bits
+		 */
+		rtc_status_reg &= ~0x07;
+		/* write 1 into SIRFSOC_RTC_AL0 to ACK the alarm interrupt */
+		rtc_status_reg |= (SIRFSOC_RTC_AL0);
+		/* Clear the Alarm enable bit */
+		rtc_status_reg &= ~(SIRFSOC_RTC_AL0E);
+	}
+	sirfsoc_rtc_iobrg_writel(rtc_status_reg, rtcdrv->rtc_base + RTC_STATUS);
+	/* this should wake up any apps polling/waiting on the read
+	 * after setting the alarm
+	 */
+	events |= RTC_IRQF | RTC_AF;
+	rtc_update_irq(rtcdrv->rtc, 1, events);
+
+	return IRQ_HANDLED;
+}
+
+static const struct of_device_id sirfsoc_rtc_of_match[] = {
+	{ .compatible = "sirf,prima2-sysrtc"},
+	{},
+};
+MODULE_DEVICE_TABLE(of, sirfsoc_rtc_of_match);
+
+static int sirfsoc_rtc_probe(struct platform_device *pdev)
+{
+	int err;
+	unsigned long rtc_div;
+	struct sirfsoc_rtc_drv *rtcdrv;
+	struct device_node *np = pdev->dev.of_node;
+
+	rtcdrv = devm_kzalloc(&pdev->dev,
+		sizeof(struct sirfsoc_rtc_drv), GFP_KERNEL);
+	if (rtcdrv == NULL) {
+		dev_err(&pdev->dev,
+			"%s: can't alloc mem for drv struct\n",
+			pdev->name);
+		return -ENOMEM;
+	}
+
+	err = of_property_read_u32(np, "reg", &rtcdrv->rtc_base);
+	if (err) {
+		dev_err(&pdev->dev, "unable to find base address of rtc node in dtb\n");
+		goto error;
+	}
+
+	platform_set_drvdata(pdev, rtcdrv);
+
+	/* Register rtc alarm as a wakeup source */
+	device_init_wakeup(&pdev->dev, 1);
+
+	/*
+	 * Set SYS_RTC counter in RTC_HZ HZ Units
+	 * We are using 32K RTC crystal (32768 / RTC_HZ / 2) -1
+	 * If 16HZ, therefore RTC_DIV = 1023;
+	 */
+	rtc_div = ((32768 / RTC_HZ) / 2) - 1;
+	sirfsoc_rtc_iobrg_writel(rtc_div, rtcdrv->rtc_base + RTC_DIV);
+
+	rtcdrv->rtc = rtc_device_register(pdev->name, &(pdev->dev),
+			&sirfsoc_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtcdrv->rtc)) {
+		err = PTR_ERR(rtcdrv->rtc);
+		dev_err(&pdev->dev, "can't register RTC device\n");
+		return err;
+	}
+
+	/* 0x3 -> RTC_CLK */
+	sirfsoc_rtc_iobrg_writel(SIRFSOC_RTC_CLK,
+			rtcdrv->rtc_base + RTC_CLOCK_SWITCH);
+
+	/* reset SYS RTC ALARM0 */
+	sirfsoc_rtc_iobrg_writel(0x0, rtcdrv->rtc_base + RTC_ALARM0);
+
+	/* reset SYS RTC ALARM1 */
+	sirfsoc_rtc_iobrg_writel(0x0, rtcdrv->rtc_base + RTC_ALARM1);
+
+	/* Restore RTC Overflow From Register After Command Reboot */
+	rtcdrv->overflow_rtc =
+		sirfsoc_rtc_iobrg_readl(rtcdrv->rtc_base + RTC_SW_VALUE);
+
+	rtcdrv->irq = platform_get_irq(pdev, 0);
+	err = devm_request_irq(
+			&pdev->dev,
+			rtcdrv->irq,
+			sirfsoc_rtc_irq_handler,
+			IRQF_SHARED,
+			pdev->name,
+			rtcdrv);
+	if (err) {
+		dev_err(&pdev->dev, "Unable to register for the SiRF SOC RTC IRQ\n");
+		goto error;
+	}
+
+	return 0;
+
+error:
+	if (rtcdrv->rtc)
+		rtc_device_unregister(rtcdrv->rtc);
+
+	return err;
+}
+
+static int sirfsoc_rtc_remove(struct platform_device *pdev)
+{
+	struct sirfsoc_rtc_drv *rtcdrv = platform_get_drvdata(pdev);
+
+	device_init_wakeup(&pdev->dev, 0);
+	rtc_device_unregister(rtcdrv->rtc);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+
+static int sirfsoc_rtc_suspend(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct sirfsoc_rtc_drv *rtcdrv = platform_get_drvdata(pdev);
+	rtcdrv->overflow_rtc =
+		sirfsoc_rtc_iobrg_readl(rtcdrv->rtc_base + RTC_SW_VALUE);
+
+	rtcdrv->saved_counter =
+		sirfsoc_rtc_iobrg_readl(rtcdrv->rtc_base + RTC_CN);
+	rtcdrv->saved_overflow_rtc = rtcdrv->overflow_rtc;
+	if (device_may_wakeup(&pdev->dev))
+		enable_irq_wake(rtcdrv->irq);
+
+	return 0;
+}
+
+static int sirfsoc_rtc_freeze(struct device *dev)
+{
+	sirfsoc_rtc_suspend(dev);
+
+	return 0;
+}
+
+static int sirfsoc_rtc_thaw(struct device *dev)
+{
+	u32 tmp;
+	struct sirfsoc_rtc_drv *rtcdrv;
+	rtcdrv = (struct sirfsoc_rtc_drv *)dev_get_drvdata(dev);
+
+	/*
+	 * if resume from snapshot and the rtc power is losed,
+	 * restroe the rtc settings
+	 */
+	if (SIRFSOC_RTC_CLK != sirfsoc_rtc_iobrg_readl(
+			rtcdrv->rtc_base + RTC_CLOCK_SWITCH)) {
+		u32 rtc_div;
+		/* 0x3 -> RTC_CLK */
+		sirfsoc_rtc_iobrg_writel(SIRFSOC_RTC_CLK,
+			rtcdrv->rtc_base + RTC_CLOCK_SWITCH);
+		/*
+		 * Set SYS_RTC counter in RTC_HZ HZ Units
+		 * We are using 32K RTC crystal (32768 / RTC_HZ / 2) -1
+		 * If 16HZ, therefore RTC_DIV = 1023;
+		 */
+		rtc_div = ((32768 / RTC_HZ) / 2) - 1;
+
+		sirfsoc_rtc_iobrg_writel(rtc_div, rtcdrv->rtc_base + RTC_DIV);
+
+		/* reset SYS RTC ALARM0 */
+		sirfsoc_rtc_iobrg_writel(0x0, rtcdrv->rtc_base + RTC_ALARM0);
+
+		/* reset SYS RTC ALARM1 */
+		sirfsoc_rtc_iobrg_writel(0x0, rtcdrv->rtc_base + RTC_ALARM1);
+	}
+	rtcdrv->overflow_rtc = rtcdrv->saved_overflow_rtc;
+
+	/*
+	 * if current counter is small than previous,
+	 * it means overflow in sleep
+	 */
+	tmp = sirfsoc_rtc_iobrg_readl(rtcdrv->rtc_base + RTC_CN);
+	if (tmp <= rtcdrv->saved_counter)
+		rtcdrv->overflow_rtc++;
+	/*
+	 *PWRC Value Be Changed When Suspend, Restore Overflow
+	 * In Memory To Register
+	 */
+	sirfsoc_rtc_iobrg_writel(rtcdrv->overflow_rtc,
+			rtcdrv->rtc_base + RTC_SW_VALUE);
+
+	return 0;
+}
+
+static int sirfsoc_rtc_resume(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct sirfsoc_rtc_drv *rtcdrv = platform_get_drvdata(pdev);
+	sirfsoc_rtc_thaw(dev);
+	if (device_may_wakeup(&pdev->dev))
+		disable_irq_wake(rtcdrv->irq);
+
+	return 0;
+}
+
+static int sirfsoc_rtc_restore(struct device *dev)
+{
+	struct platform_device *pdev = to_platform_device(dev);
+	struct sirfsoc_rtc_drv *rtcdrv = platform_get_drvdata(pdev);
+
+	if (device_may_wakeup(&pdev->dev))
+		disable_irq_wake(rtcdrv->irq);
+	return 0;
+}
+
+#else
+#define sirfsoc_rtc_suspend	NULL
+#define sirfsoc_rtc_resume	NULL
+#define sirfsoc_rtc_freeze	NULL
+#define sirfsoc_rtc_thaw	NULL
+#define sirfsoc_rtc_restore	NULL
+#endif
+
+static const struct dev_pm_ops sirfsoc_rtc_pm_ops = {
+	.suspend = sirfsoc_rtc_suspend,
+	.resume = sirfsoc_rtc_resume,
+	.freeze = sirfsoc_rtc_freeze,
+	.thaw = sirfsoc_rtc_thaw,
+	.restore = sirfsoc_rtc_restore,
+};
+
+static struct platform_driver sirfsoc_rtc_driver = {
+	.driver = {
+		.name = "sirfsoc-rtc",
+		.owner = THIS_MODULE,
+#ifdef CONFIG_PM
+		.pm = &sirfsoc_rtc_pm_ops,
+#endif
+		.of_match_table = of_match_ptr(sirfsoc_rtc_of_match),
+	},
+	.probe = sirfsoc_rtc_probe,
+	.remove = sirfsoc_rtc_remove,
+};
+module_platform_driver(sirfsoc_rtc_driver);
+
+MODULE_DESCRIPTION("SiRF SoC rtc driver");
+MODULE_AUTHOR("Xianglong Du <Xianglong.Du@csr.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:sirfsoc-rtc");