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>

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