[PATCH] mtd: nand: Fix problem with NAND_CMD_RNDOUT (05h-E0h)

[Pekon Gupta]

From: Bacem Daassi <Bacem.Daassi at spansion.com>

Though the NAND_CMD_READ "Page Read" command expects the full address footprint
(2bytes for column address + 3bytes for row address).
But once the page is loaded into the read buffer, NAND_CMD_RNDOUT (05h-E0h) also
called "Random Data Output" command expects to see only the column address that
should be addressed within the already loaded page present in read buffers.
Only 2 address cycles with ALE active should be provided between the 05h and E0h
So expected sequence for NAND_CMD_RNDOUT is
	<05h> <column-addr-byte1> <column-address-byte2> <E0h>

Though most NAND Devices mentioned above tend to work even if extra cycles of
page-address is issued between <05h> .... <E0h> command. But some Spansion and
Hynix devices break on this non-compliance.
The same issue has been reported by Bacem Daassi
  http://e2e.ti.com/support/arm/sitara_arm/f/791/t/259699.aspx

This patch fixes nand_command for all vendors devices as datasheet of all
devices expect same sequence.

+--------+------------------------+---------------------------------------------
|Vendor  | Datasheet/Part#        |  Reference
+--------+------------------------+---------------------------------------------
|Spansion| S34ML{01|02|04}G2      | Figure 6.12 Random Data Output In a Page
|Micron  | MT29F{16|32|64|128}G08A| Figure 47: CHANGE READ COLUMN (05h-E0h) Operation
|Macronix| MX30LF1G08AA           | Figure 10. AC Waveforms for Random Data Output
|Toshiba | TC58NVG1S3ETAI0        | Figure Column Address Change in Read Cycle Timing Diagram (2/2)
+--------+------------------------+---------------------------------------------

Reported-by: Bacem Daassi <Bacem.Daassi at spansion.com>
Reported-by: Marek Belisko <marek.belisko at gmail.com>
Reported-by: Steven Kipisz <s-kipisz2 at ti.com>
Signed-off-by: Pekon Gupta <pekon at ti.com>
---
 drivers/mtd/nand/nand_base.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 9d01c4d..f0cb33a 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -688,7 +688,7 @@ static void nand_command_lp(struct mtd_info *mtd, unsigned int command,
 			ctrl &= ~NAND_CTRL_CHANGE;
 			chip->cmd_ctrl(mtd, column >> 8, ctrl);
 		}
-		if (page_addr != -1) {
+		if (page_addr != -1 && command != NAND_CMD_RNDOUT) {
 			chip->cmd_ctrl(mtd, page_addr, ctrl);
 			chip->cmd_ctrl(mtd, page_addr >> 8,
 				       NAND_NCE | NAND_ALE);
-- 
1.8.5.1.163.gd7aced9