x86: rtc: mc146818: Add helpers to read/write CMOS RAM

On x86 we use CMOS RAM to read and write some settings. Add basic support
for this, including access to registers 128-255.

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

1 files changed, 32 insertions, 0 deletions

diff --git a/include/rtc.h b/include/rtc.h
index d11aa8baf91..54e361ea5e8 100644
--- a/include/rtc.h
+++ b/include/rtc.h
@@ -51,6 +51,38 @@ unsigned long mktime (unsigned int, unsigned int, unsigned int,
 		      unsigned int, unsigned int, unsigned int);
 
 /**
+ * rtc_read8() - Read an 8-bit register
+ *
+ * @reg:	Register to read
+ * @return value read
+ */
+int rtc_read8(int reg);
+
+/**
+ * rtc_write8() - Write an 8-bit register
+ *
+ * @reg:	Register to write
+ * @value:	Value to write
+ */
+void rtc_write8(int reg, uchar val);
+
+/**
+ * rtc_read32() - Read a 32-bit value from the RTC
+ *
+ * @reg:	Offset to start reading from
+ * @return value read
+ */
+u32 rtc_read32(int reg);
+
+/**
+ * rtc_write32() - Write a 32-bit value to the RTC
+ *
+ * @reg:	Register to start writing to
+ * @value:	Value to write
+ */
+void rtc_write32(int reg, u32 value);
+
+/**
  * rtc_init() - Set up the real time clock ready for use
  */
 void rtc_init(void);