[PATCH v3 1/8] MTD: xway: add some more documentation

[Hauke Mehrtens]

This adds some register documentation which should make it easier to
understand how this controller works.

Signed-off-by: Hauke Mehrtens <hauke at hauke-m.de>
---
 drivers/mtd/nand/xway_nand.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/nand/xway_nand.c b/drivers/mtd/nand/xway_nand.c
index 0cf0ac0..2d74637 100644
--- a/drivers/mtd/nand/xway_nand.c
+++ b/drivers/mtd/nand/xway_nand.c
@@ -16,20 +16,29 @@
 #define EBU_ADDSEL1		0x24
 #define EBU_NAND_CON		0xB0
 #define EBU_NAND_WAIT		0xB4
+#define  NAND_WAIT_RD		BIT(0) /* NAND flash status output */
+#define  NAND_WAIT_WR_C		BIT(3) /* NAND Write/Read complete */
 #define EBU_NAND_ECC0		0xB8
 #define EBU_NAND_ECC_AC		0xBC
 
-/* nand commands */
-#define NAND_CMD_ALE		(1 << 2)
-#define NAND_CMD_CLE		(1 << 3)
-#define NAND_CMD_CS		(1 << 4)
+/*
+ * nand commands
+ * The pins of the NAND chip are selected based on the address bits of the
+ * "register" read and write. There are no special registers, but an
+ * address range and the lower address bits are used to activate the
+ * correct line. For example when the bit (1 << 2) is set in the address
+ * the ALE pin will be activated.
+ */
+#define NAND_CMD_ALE		BIT(2) /* address latch enable */
+#define NAND_CMD_CLE		BIT(3) /* command latch enable */
+#define NAND_CMD_CS		BIT(4) /* chip select */
+#define NAND_CMD_SE		BIT(5) /* spare area access latch */
+#define NAND_CMD_WP		BIT(6) /* write protect */
 #define NAND_WRITE_CMD_RESET	0xff
 #define NAND_WRITE_CMD		(NAND_CMD_CS | NAND_CMD_CLE)
 #define NAND_WRITE_ADDR		(NAND_CMD_CS | NAND_CMD_ALE)
 #define NAND_WRITE_DATA		(NAND_CMD_CS)
 #define NAND_READ_DATA		(NAND_CMD_CS)
-#define NAND_WAIT_WR_C		(1 << 3)
-#define NAND_WAIT_RD		(0x1)
 
 /* we need to tel the ebu which addr we mapped the nand to */
 #define ADDSEL1_MASK(x)		(x << 4)
-- 
2.8.1