i2c: iproc: Fix i2c master read more than 63 bytes

Use SMBUS_MASTER_DATA_READ.MASTER_RD_STATUS bit to check for RX
FIFO empty condition because SMBUS_MASTER_FIFO_CONTROL.MASTER_RX_PKT_COUNT
is not updated for read >= 64 bytes. This fixes the issue when trying to
read from the I2C slave more than 63 bytes.

Fixes: c24b8d5 ("i2c: iproc: Extend I2C read up to 255 bytes")
Cc: stable@kernel.org
Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Author: rayagonda

drivers/i2c/busses/i2c-bcm-iproc.c

@@ -392,16 +392,18 @@ static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev *iproc_i2c,
 static void bcm_iproc_i2c_read_valid_bytes(struct bcm_iproc_i2c_dev *iproc_i2c)
 {
 	struct i2c_msg *msg = iproc_i2c->msg;
+	uint32_t val;
 
 	/* Read valid data from RX FIFO */
 	while (iproc_i2c->rx_bytes < msg->len) {
-		if (!((iproc_i2c_rd_reg(iproc_i2c, M_FIFO_CTRL_OFFSET) >> M_FIFO_RX_CNT_SHIFT)
-		      & M_FIFO_RX_CNT_MASK))
+		val = iproc_i2c_rd_reg(iproc_i2c, M_RX_OFFSET);
+
+		/* rx fifo empty */
+		if (!((val >> M_RX_STATUS_SHIFT) & M_RX_STATUS_MASK))
 			break;
 
 		msg->buf[iproc_i2c->rx_bytes] =
-			(iproc_i2c_rd_reg(iproc_i2c, M_RX_OFFSET) >>
-			M_RX_DATA_SHIFT) & M_RX_DATA_MASK;
+			(val >> M_RX_DATA_SHIFT) & M_RX_DATA_MASK;
 		iproc_i2c->rx_bytes++;
 	}
 }