From: Quan Nguyen <quan@os.amperecomputing.com>

Commit 0daede80f870 ("i2c: designware: Convert driver to using regmap API")
changes the logic to validate the whole 32-bit return value of
DW_IC_DATA_CMD register instead of 8-bit LSB without reason.

Later, commit f53f15ba5a85 ("i2c: designware: Get right data length"),
introduced partial fix but not enough because the "tmp > 0" still test
tmp as 32-bit value and is wrong in case the IC_DATA_CMD[11] is set.

Revert the logic to just before commit 0daede80f870
("i2c: designware: Convert driver to using regmap API").

Fixes: f53f15ba5a85 ("i2c: designware: Get right data length")
Fixes: 0daede80f870 ("i2c: designware: Convert driver to using regmap API")
Cc: stable@vger.kernel.org
Signed-off-by: Tam Nguyen <tamnguyenchi@os.amperecomputing.com>
Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
---
 drivers/i2c/busses/i2c-designware-master.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c
index 55ea91a63382..e96276d1b002 100644
--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -526,9 +526,10 @@ i2c_dw_read(struct dw_i2c_dev *dev)
 			u32 flags = msgs[dev->msg_read_idx].flags;
 
 			regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
+			tmp &= DW_IC_DATA_CMD_DAT;
 			/* Ensure length byte is a valid value */
 			if (flags & I2C_M_RECV_LEN &&
-			    (tmp & DW_IC_DATA_CMD_DAT) <= I2C_SMBUS_BLOCK_MAX && tmp > 0) {
+			    tmp <= I2C_SMBUS_BLOCK_MAX && tmp > 0) {
 				len = i2c_dw_recv_len(dev, tmp);
 			}
 			*buf++ = tmp;
-- 
2.25.1

On Wed, Jul 26, 2023 at 03:00:00PM +0700, Tam Nguyen wrote:
> From: Quan Nguyen <quan@os.amperecomputing.com>
> 
> Commit 0daede80f870 ("i2c: designware: Convert driver to using regmap API")
> changes the logic to validate the whole 32-bit return value of
> DW_IC_DATA_CMD register instead of 8-bit LSB without reason.
> 
> Later, commit f53f15ba5a85 ("i2c: designware: Get right data length"),
> introduced partial fix but not enough because the "tmp > 0" still test
> tmp as 32-bit value and is wrong in case the IC_DATA_CMD[11] is set.
> 
> Revert the logic to just before commit 0daede80f870
> ("i2c: designware: Convert driver to using regmap API").
> 
> Fixes: f53f15ba5a85 ("i2c: designware: Get right data length")
> Fixes: 0daede80f870 ("i2c: designware: Convert driver to using regmap API")
> Cc: stable@vger.kernel.org
> Signed-off-by: Tam Nguyen <tamnguyenchi@os.amperecomputing.com>
> Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>

Applied to for-current, thanks!

On 7/26/23 11:00, Tam Nguyen wrote:
> From: Quan Nguyen <quan@os.amperecomputing.com>
> 
> Commit 0daede80f870 ("i2c: designware: Convert driver to using regmap API")
> changes the logic to validate the whole 32-bit return value of
> DW_IC_DATA_CMD register instead of 8-bit LSB without reason.
> 
> Later, commit f53f15ba5a85 ("i2c: designware: Get right data length"),
> introduced partial fix but not enough because the "tmp > 0" still test
> tmp as 32-bit value and is wrong in case the IC_DATA_CMD[11] is set.
> 
> Revert the logic to just before commit 0daede80f870
> ("i2c: designware: Convert driver to using regmap API").
> 
> Fixes: f53f15ba5a85 ("i2c: designware: Get right data length")
> Fixes: 0daede80f870 ("i2c: designware: Convert driver to using regmap API")
> Cc: stable@vger.kernel.org
> Signed-off-by: Tam Nguyen <tamnguyenchi@os.amperecomputing.com>
> Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
> ---
>   drivers/i2c/busses/i2c-designware-master.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>