x86: Add an early CMOS access library

This adds a library that provides CMOS (inside RTC SRAM) access
at a very early stage when driver model is not available yet.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Stefan Roese <sr@denx.de>

1 files changed, 43 insertions, 0 deletions

diff --git a/arch/x86/include/asm/early_cmos.h b/arch/x86/include/asm/early_cmos.h
new file mode 100644
index 0000000000..cd2634d4cd
--- /dev/null
+++ b/arch/x86/include/asm/early_cmos.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2017, Bin Meng <bmeng.cn@gmail.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __EARLY_CMOS_H
+#define __EARLY_CMOS_H
+
+/* CMOS actually resides in the RTC SRAM */
+#define CMOS_IO_PORT	0x70
+
+/**
+ * cmos_read8() - Get 8-bit data stored at the given address
+ *
+ * This reads from CMOS for the 8-bit data stored at the given address.
+ *
+ * @addr:	RTC SRAM address
+ * @return:	8-bit data stored at the given address
+ */
+u8 cmos_read8(u8 addr);
+
+/**
+ * cmos_read16() - Get 16-bit data stored at the given address
+ *
+ * This reads from CMOS for the 16-bit data stored at the given address.
+ *
+ * @addr:	RTC SRAM address
+ * @return:	16-bit data stored at the given address
+ */
+u16 cmos_read16(u8 addr);
+
+/**
+ * cmos_read32() - Get 32-bit data stored at the given address
+ *
+ * This reads from CMOS for the 32-bit data stored at the given address.
+ *
+ * @addr:	RTC SRAM address
+ * @return:	32-bit data stored at the given address
+ */
+u32 cmos_read32(u8 addr);
+
+#endif /* __EARLY_CMOS_H */