[PATCH 1/2] rtc: Add ASPEED RTC driver

[Joel Stanley]

Read and writes the time to the non-battery backed RTC in the ASPEED
AST2400 and AST2500 system on chip.

Signed-off-by: Joel Stanley <joel at jms.id.au>
---
 drivers/rtc/Kconfig      |  10 +++
 drivers/rtc/Makefile     |   1 +
 drivers/rtc/rtc-aspeed.c | 142 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 153 insertions(+)
 create mode 100644 drivers/rtc/rtc-aspeed.c

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index a819ef07b7ec..372944b59b69 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1783,6 +1783,16 @@ config RTC_DRV_RTD119X
 	  If you say yes here, you get support for the RTD1295 SoC
 	  Real Time Clock.
 
+config RTC_DRV_ASPEED
+	tristate "Aspeed RTC"
+	depends on ARCH_ASPEED || COMPILE_TEST
+	help
+	  If you say yes here you get support for the ASPEED AST2400 and
+	  AST2500 SoC real time clocks.
+
+	  This driver can also be built as a module, if so, the module
+	  will be called "rtc-aspeed".
+
 comment "HID Sensor RTC drivers"
 
 config RTC_DRV_HID_SENSOR_TIME
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 290c1730fb0a..7d924577d133 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_RTC_DRV_AC100)	+= rtc-ac100.o
 obj-$(CONFIG_RTC_DRV_ARMADA38X)	+= rtc-armada38x.o
 obj-$(CONFIG_RTC_DRV_AS3722)	+= rtc-as3722.o
 obj-$(CONFIG_RTC_DRV_ASM9260)	+= rtc-asm9260.o
+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
diff --git a/drivers/rtc/rtc-aspeed.c b/drivers/rtc/rtc-aspeed.c
new file mode 100644
index 000000000000..dce00e594910
--- /dev/null
+++ b/drivers/rtc/rtc-aspeed.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0+
+// Copyright 2015 IBM Corp.
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/io.h>
+
+struct aspeed_rtc {
+	struct rtc_device	*rtc_dev;
+	void __iomem		*base;
+	spinlock_t		lock;
+};
+
+#define RTC_TIME	0x00
+#define RTC_YEAR	0x04
+#define RTC_CTRL	0x10
+
+#define RTC_UNLOCK	0x02
+#define RTC_ENABLE	0x01
+
+static int aspeed_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct aspeed_rtc *rtc = dev_get_drvdata(dev);
+	unsigned int cent, year, mon, day, hour, min, sec;
+	unsigned long flags;
+	u32 reg1, reg2;
+
+	spin_lock_irqsave(&rtc->lock, flags);
+
+	do {
+		reg2 = readl(rtc->base + RTC_YEAR);
+		reg1 = readl(rtc->base + RTC_TIME);
+	} while (reg2 != readl(rtc->base + RTC_YEAR));
+
+	day  = (reg1 >> 24) & 0x1f;
+	hour = (reg1 >> 16) & 0x1f;
+	min  = (reg1 >>  8) & 0x3f;
+	sec  = (reg1 >>  0) & 0x3f;
+	cent = (reg2 >> 16) & 0x1f;
+	year = (reg2 >>  8) & 0x7f;
+	/*
+	 * Month is 1-12 in hardware, and 0-11 in struct rtc_time, however we
+	 * are using mktime64 which is 1-12, so no adjustment is necessary
+	 */
+	mon  = (reg2 >>  0) & 0x0f;
+
+	rtc_time64_to_tm(mktime64(cent * 100 + year, mon, day, hour, min, sec),
+			tm);
+
+	spin_unlock_irqrestore(&rtc->lock, flags);
+
+	return 0;
+}
+
+static int aspeed_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct aspeed_rtc *rtc = dev_get_drvdata(dev);
+	unsigned long flags;
+	u32 reg1, reg2, ctrl;
+	int year, cent;
+
+	spin_lock_irqsave(&rtc->lock, flags);
+
+	cent = (tm->tm_year + 1900) / 100;
+	year = tm->tm_year % 100;
+
+	reg1 = (tm->tm_mday << 24) | (tm->tm_hour << 16) | (tm->tm_min << 8) |
+		tm->tm_sec;
+
+	/* Hardware is 1-12, convert to 0-11 */
+	reg2 = ((cent & 0x1f) << 16) | ((year & 0x7f) << 8) |
+		((tm->tm_mon & 0xf) + 1);
+
+	ctrl = readl(rtc->base + RTC_CTRL);
+	writel(ctrl | RTC_UNLOCK, rtc->base + RTC_CTRL);
+
+	writel(reg1, rtc->base + RTC_TIME);
+	writel(reg2, rtc->base + RTC_YEAR);
+
+	writel(ctrl, rtc->base + RTC_CTRL);
+
+	spin_unlock_irqrestore(&rtc->lock, flags);
+
+	return 0;
+}
+
+static const struct rtc_class_ops aspeed_rtc_ops = {
+	.read_time = aspeed_rtc_read_time,
+	.set_time = aspeed_rtc_set_time,
+};
+
+static int aspeed_rtc_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	struct aspeed_rtc *rtc;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	rtc->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(rtc->base))
+		return PTR_ERR(rtc->base);
+
+	platform_set_drvdata(pdev, rtc);
+
+	rtc->rtc_dev = devm_rtc_device_register(&pdev->dev, pdev->name,
+						&aspeed_rtc_ops, THIS_MODULE);
+
+	if (IS_ERR(rtc->rtc_dev))
+		return PTR_ERR(rtc->rtc_dev);
+
+	spin_lock_init(&rtc->lock);
+
+	/* Enable RTC and clear the unlock bit */
+	writel(RTC_ENABLE, rtc->base + RTC_CTRL);
+
+	return 0;
+}
+
+static const struct of_device_id aspeed_rtc_match[] = {
+	{ .compatible = "aspeed,ast2400-rtc", },
+	{ .compatible = "aspeed,ast2500-rtc", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, aspeed_rtc_match);
+
+static struct platform_driver aspeed_rtc_driver = {
+	.driver = {
+		.name = "aspeed-rtc",
+		.of_match_table = of_match_ptr(aspeed_rtc_match),
+	},
+};
+
+module_platform_driver_probe(aspeed_rtc_driver, aspeed_rtc_probe);
+
+MODULE_DESCRIPTION("Aspeed RTC driver");
+MODULE_AUTHOR("Joel Stanley <joel at jms.id.au>");
+MODULE_LICENSE("GPL");
-- 
2.17.1