i2c: designware: Get right data length

IC_DATA_CMD[11] indicates the first data byte received after the address
phase for receive transfer in Master receiver or Slave receiver mode,
this bit was set in some transfer flow. IC_DATA_CMD[7:0] contains the
data to be transmitted or received on the I2C bus, so we should use the
lower 8 bits to get the real data length.
Signed-off-by: Liguang Zhang <zhangliguang@linux.alibaba.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-designware-core.h

@@ -38,6 +38,8 @@
 #define DW_IC_CON_TX_EMPTY_CTRL			BIT(8)
 #define DW_IC_CON_RX_FIFO_FULL_HLD_CTRL		BIT(9)
 
+#define DW_IC_DATA_CMD_DAT			GENMASK(7, 0)
+
 /*
  * Registers offset
  */

drivers/i2c/busses/i2c-designware-master.c

@@ -432,7 +432,7 @@ i2c_dw_read(struct dw_i2c_dev *dev)
 			regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
 			/* Ensure length byte is a valid value */
 			if (flags & I2C_M_RECV_LEN &&
-			    tmp <= I2C_SMBUS_BLOCK_MAX && tmp > 0) {
+			    (tmp & DW_IC_DATA_CMD_DAT) <= I2C_SMBUS_BLOCK_MAX && tmp > 0) {
 				len = i2c_dw_recv_len(dev, tmp);
 			}
 			*buf++ = tmp;