[PATCH v2] mtd: nand: fix interpretation of NAND_CMD_NONE in nand_command[_lp]()

[Miquel Raynal]

Some drivers (like nand_hynix.c) call ->cmdfunc() with NAND_CMD_NONE
and a column address and expect the controller to only send address
cycles. Right now, the default ->cmdfunc() implementations provided by
the core do not filter out the command cycle in this case and forwards
the request to the controller driver through the ->cmd_ctrl() method.
The thing is, NAND controller drivers can get this wrong and send a
command cycle with a NAND_CMD_NONE opcode and since NAND_CMD_NONE is
-1, and the command field is usually casted to an u8, we end up sending
the 0xFF command which is actually a RESET operation.

Add conditions in nand_command[_lp]() functions to sending the initial
command cycle when command == NAND_CMD_NONE.

Signed-off-by: Miquel Raynal <miquel.raynal at free-electrons.com>
---

Hello,

Changes since v1:
  - Commit message rewording.
  - Added a case for NAND_CMD_NONE in the switch statement of each
    function to avoid unnecesary wait.

Thanks,
Miquèl


 drivers/mtd/nand/nand_base.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index e48bf8260f54..074b67571bfc 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -710,7 +710,8 @@ static void nand_command(struct mtd_info *mtd, unsigned int command,
 		chip->cmd_ctrl(mtd, readcmd, ctrl);
 		ctrl &= ~NAND_CTRL_CHANGE;
 	}
-	chip->cmd_ctrl(mtd, command, ctrl);
+	if (command != NAND_CMD_NONE)
+		chip->cmd_ctrl(mtd, command, ctrl);
 
 	/* Address cycle, when necessary */
 	ctrl = NAND_CTRL_ALE | NAND_CTRL_CHANGE;
@@ -738,6 +739,7 @@ static void nand_command(struct mtd_info *mtd, unsigned int command,
 	 */
 	switch (command) {
 
+	case NAND_CMD_NONE:
 	case NAND_CMD_PAGEPROG:
 	case NAND_CMD_ERASE1:
 	case NAND_CMD_ERASE2:
@@ -831,7 +833,9 @@ static void nand_command_lp(struct mtd_info *mtd, unsigned int command,
 	}
 
 	/* Command latch cycle */
-	chip->cmd_ctrl(mtd, command, NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
+	if (command != NAND_CMD_NONE)
+		chip->cmd_ctrl(mtd, command,
+			       NAND_NCE | NAND_CLE | NAND_CTRL_CHANGE);
 
 	if (column != -1 || page_addr != -1) {
 		int ctrl = NAND_CTRL_CHANGE | NAND_NCE | NAND_ALE;
@@ -866,6 +870,7 @@ static void nand_command_lp(struct mtd_info *mtd, unsigned int command,
 	 */
 	switch (command) {
 
+	case NAND_CMD_NONE:
 	case NAND_CMD_CACHEDPROG:
 	case NAND_CMD_PAGEPROG:
 	case NAND_CMD_ERASE1:
-- 
2.11.0