[RFC] mtd: nand_base: Make Diskonchip work again

[Alexander Shiyan]

According to my post (http://permalink.gmane.org/gmane.linux.drivers.mtd/45657),
I created a patch to fix the DiskOnChip regression. Patch partially revert
"mtd: nand: kill NAND_NO_READRDY". We create NAND_NEED_READDRY option as a
replacement NAND_NO_READRDY but with different logic, and restore RDY
expectations in reading function, if this option is set. At least, Disconchip
works again, so probably it can help in solving other NAND-related bugs in
the latest kernels.

Signed-off-by: Alexander Shiyan <shc_work at mail.ru>
---
 drivers/mtd/nand/diskonchip.c |    1 +
 drivers/mtd/nand/nand_base.c  |   16 ++++++++++++++++
 include/linux/mtd/nand.h      |    2 ++
 3 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/drivers/mtd/nand/diskonchip.c b/drivers/mtd/nand/diskonchip.c
index 81fa578..19992f2 100644
--- a/drivers/mtd/nand/diskonchip.c
+++ b/drivers/mtd/nand/diskonchip.c
@@ -1580,6 +1580,7 @@ static int __init doc_probe(unsigned long physadr)
 	nand->dev_ready		= doc200x_dev_ready;
 	nand->waitfunc		= doc200x_wait;
 	nand->block_bad		= doc200x_block_bad;
+	nand->options		= NAND_NEED_READRDY;
 	nand->ecc.hwctl		= doc200x_enable_hwecc;
 	nand->ecc.calculate	= doc200x_calculate_ecc;
 	nand->ecc.correct	= doc200x_correct_data;
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 4321415..42c6392 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1523,6 +1523,14 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
 					oobreadlen -= toread;
 				}
 			}
+
+			if (chip->options & NAND_NEED_READRDY) {
+				/* Apply delay or wait for ready/busy pin */
+				if (!chip->dev_ready)
+					udelay(chip->chip_delay);
+				else
+					nand_wait_ready(mtd);
+			}
 		} else {
 			memcpy(buf, chip->buffers->databuf + col, bytes);
 			buf += bytes;
@@ -1787,6 +1795,14 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
 		len = min(len, readlen);
 		buf = nand_transfer_oob(chip, buf, ops, len);
 
+		if (chip->options & NAND_NEED_READRDY) {
+			/* Apply delay or wait for ready/busy pin */
+			if (!chip->dev_ready)
+				udelay(chip->chip_delay);
+			else
+				nand_wait_ready(mtd);
+		}
+
 		readlen -= len;
 		if (!readlen)
 			break;
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 7ccb3c5..1c13582 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -187,6 +187,8 @@ typedef enum {
  * This happens with the Renesas AG-AND chips, possibly others.
  */
 #define BBT_AUTO_REFRESH	0x00000080
+/* Chip require ready check on read */
+#define NAND_NEED_READRDY	0x00000100
 /* Chip does not allow subpage writes */
 #define NAND_NO_SUBPAGE_WRITE	0x00000200
 
-- 
1.7.3.4