dm: rtc: Add a uclass for real-time clocks

Add a uclass for real-time clocks which support getting the current time,
setting it and resetting the chip to a known-working state. Some RTCs have
additional registers which can be used to store settings, so also provide
an interface to these.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/rtc/Kconfig

@@ -0,0 +1,8 @@
+config DM_RTC
+	bool "Enable Driver Model for RTC drivers"
+	depends on DM
+	help
+	  Enable drver model for real-time-clock drivers. The RTC uclass
+	  then provides the rtc_get()/rtc_set() interface, delegating to
+	  drivers to perform the actual functions. See rtc.h for a
+	  description of the API.

drivers/rtc/Makefile

@@ -7,6 +7,8 @@
 
 #ccflags-y += -DDEBUG
 
+obj-$(CONFIG_DM_RTC) += rtc-uclass.o
+
 obj-$(CONFIG_RTC_AT91SAM9_RTT) += at91sam9_rtt.o
 obj-$(CONFIG_RTC_BFIN) += bfin_rtc.o
 obj-y += date.o

drivers/rtc/rtc-uclass.c

@@ -0,0 +1,96 @@
+/*
+ * (C) Copyright 2015 Google, Inc
+ * Written by Simon Glass <sjg@chromium.org>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <errno.h>
+#include <rtc.h>
+
+int dm_rtc_get(struct udevice *dev, struct rtc_time *time)
+{
+	struct rtc_ops *ops = rtc_get_ops(dev);
+
+	assert(ops);
+	if (!ops->get)
+		return -ENOSYS;
+	return ops->get(dev, time);
+}
+
+int dm_rtc_set(struct udevice *dev, struct rtc_time *time)
+{
+	struct rtc_ops *ops = rtc_get_ops(dev);
+
+	assert(ops);
+	if (!ops->set)
+		return -ENOSYS;
+	return ops->set(dev, time);
+}
+
+int dm_rtc_reset(struct udevice *dev)
+{
+	struct rtc_ops *ops = rtc_get_ops(dev);
+
+	assert(ops);
+	if (!ops->reset)
+		return -ENOSYS;
+	return ops->reset(dev);
+}
+
+int rtc_read8(struct udevice *dev, unsigned int reg)
+{
+	struct rtc_ops *ops = rtc_get_ops(dev);
+
+	assert(ops);
+	if (!ops->read8)
+		return -ENOSYS;
+	return ops->read8(dev, reg);
+}
+
+int rtc_write8(struct udevice *dev, unsigned int reg, int val)
+{
+	struct rtc_ops *ops = rtc_get_ops(dev);
+
+	assert(ops);
+	if (!ops->write8)
+		return -ENOSYS;
+	return ops->write8(dev, reg, val);
+}
+
+int rtc_read32(struct udevice *dev, unsigned int reg, u32 *valuep)
+{
+	u32 value = 0;
+	int ret;
+	int i;
+
+	for (i = 0; i < sizeof(value); i++) {
+		ret = rtc_read8(dev, reg + i);
+		if (ret)
+			return ret;
+		value |= ret << (i << 3);
+	}
+
+	*valuep = value;
+	return 0;
+}
+
+int rtc_write32(struct udevice *dev, unsigned int reg, u32 value)
+{
+	int i, ret;
+
+	for (i = 0; i < sizeof(value); i++) {
+		ret = rtc_write8(dev, reg + i, (value >> (i << 3)) & 0xff);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+UCLASS_DRIVER(rtc) = {
+	.name		= "rtc",
+	.id		= UCLASS_RTC,
+};

include/dm/uclass-id.h

@@ -46,6 +46,7 @@ enum uclass_id {
 	UCLASS_USB_DEV_GENERIC,	/* USB generic device */
 	UCLASS_MASS_STORAGE,	/* Mass storage device */
 	UCLASS_CPU,		/* CPU, typically part of an SoC */
+	UCLASS_RTC,		/* Real time clock device */
 
 	UCLASS_COUNT,
 	UCLASS_INVALID = -1,

include/rtc.h

@@ -17,6 +17,137 @@
 #include <bcd.h>
 #include <rtc_def.h>
 
+#ifdef CONFIG_DM_RTC
+
+struct rtc_ops {
+	/**
+	 * get() - get the current time
+	 *
+	 * Returns the current time read from the RTC device. The driver
+	 * is responsible for setting up every field in the structure.
+	 *
+	 * @dev:	Device to read from
+	 * @time:	Place to put the time that is read
+	 */
+	int (*get)(struct udevice *dev, struct rtc_time *time);
+
+	/**
+	 * set() - set the current time
+	 *
+	 * Sets the time in the RTC device. The driver can expect every
+	 * field to be set correctly.
+	 *
+	 * @dev:	Device to read from
+	 * @time:	Time to write
+	 */
+	int (*set)(struct udevice *dev, const struct rtc_time *time);
+
+	/**
+	 * reset() - reset the RTC to a known-good state
+	 *
+	 * This function resets the RTC to a known-good state. The time may
+	 * be unset by this method, so should be set after this method is
+	 * called.
+	 *
+	 * @dev:	Device to read from
+	 * @return 0 if OK, -ve on error
+	 */
+	int (*reset)(struct udevice *dev);
+
+	/**
+	 * read8() - Read an 8-bit register
+	 *
+	 * @dev:	Device to read from
+	 * @reg:	Register to read
+	 * @return value read, or -ve on error
+	 */
+	int (*read8)(struct udevice *dev, unsigned int reg);
+
+	/**
+	* write8() - Write an 8-bit register
+	*
+	* @dev:		Device to write to
+	* @reg:		Register to write
+	* @value:	Value to write
+	* @return 0 if OK, -ve on error
+	*/
+	int (*write8)(struct udevice *dev, unsigned int reg, int val);
+};
+
+/* Access the operations for an RTC device */
+#define rtc_get_ops(dev)	((struct rtc_ops *)(dev)->driver->ops)
+
+/**
+ * dm_rtc_get() - Read the time from an RTC
+ *
+ * @dev:	Device to read from
+ * @time:	Place to put the current time
+ * @return 0 if OK, -ve on error
+ */
+int dm_rtc_get(struct udevice *dev, struct rtc_time *time);
+
+/**
+ * dm_rtc_put() - Write a time to an RTC
+ *
+ * @dev:	Device to read from
+ * @time:	Time to write into the RTC
+ * @return 0 if OK, -ve on error
+ */
+int dm_rtc_set(struct udevice *dev, struct rtc_time *time);
+
+/**
+ * dm_rtc_reset() - reset the RTC to a known-good state
+ *
+ * If the RTC appears to be broken (e.g. it is not counting up in seconds)
+ * it may need to be reset to a known good state. This function achieves this.
+ * After resetting the RTC the time should then be set to a known value by
+ * the caller.
+ *
+ * @dev:	Device to read from
+ * @return 0 if OK, -ve on error
+ */
+int dm_rtc_reset(struct udevice *dev);
+
+/**
+ * rtc_read8() - Read an 8-bit register
+ *
+ * @dev:	Device to read from
+ * @reg:	Register to read
+ * @return value read, or -ve on error
+ */
+int rtc_read8(struct udevice *dev, unsigned int reg);
+
+/**
+ * rtc_write8() - Write an 8-bit register
+ *
+ * @dev:	Device to write to
+ * @reg:	Register to write
+ * @value:	Value to write
+ * @return 0 if OK, -ve on error
+ */
+int rtc_write8(struct udevice *dev, unsigned int reg, int val);
+
+/**
+ * rtc_read32() - Read a 32-bit value from the RTC
+ *
+ * @dev:	Device to read from
+ * @reg:	Offset to start reading from
+ * @valuep:	Place to put the value that is read
+ * @return 0 if OK, -ve on error
+ */
+int rtc_read32(struct udevice *dev, unsigned int reg, u32 *valuep);
+
+/**
+ * rtc_write32() - Write a 32-bit value to the RTC
+ *
+ * @dev:	Device to write to
+ * @reg:	Register to start writing to
+ * @value:	Value to write
+ * @return 0 if OK, -ve on error
+ */
+int rtc_write32(struct udevice *dev, unsigned int reg, u32 value);
+
+#else
 int rtc_get (struct rtc_time *);
 int rtc_set (struct rtc_time *);
 void rtc_reset (void);
@@ -57,6 +188,7 @@ void rtc_write32(int reg, u32 value);
  * rtc_init() - Set up the real time clock ready for use
  */
 void rtc_init(void);
+#endif
 
 /**
  * rtc_calc_weekday() - Work out the weekday from a time