tty: serial: fsl_lpuart: correct the FIFO depth size

VF610/LS1021a/i.MX7ULP/i.MX8QXP reference manual describe the
TXFIFOSIZE/RXFIFOSIZE field as below.

000b - FIFO/Buffer depth = 1 dataword.
001b - FIFO/Buffer depth = 4 datawords.
010b - FIFO/Buffer depth = 8 datawords.
011b - FIFO/Buffer depth = 16 datawords.
100b - FIFO/Buffer depth = 32 datawords.
101b - FIFO/Buffer depth = 64 datawords.
110b - FIFO/Buffer depth = 128 datawords.
111b - FIFO/Buffer depth = 256 datawords. (Reserved for VF610)

So the FIFO depth should be: 0x1 << (val ? (val + 1) : 0)

Signed-off-by: Fugang Duan <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serial/fsl_lpuart.c

···
 #define UARTFIFO_TXSIZE_OFF	4
 #define UARTFIFO_RXFE		0x00000008
 #define UARTFIFO_RXSIZE_OFF	0
+#define UARTFIFO_DEPTH(x)	(0x1 << ((x) ? ((x) + 1) : 0))
 
 #define UARTWATER_COUNT_MASK	0xff
 #define UARTWATER_TXCNT_OFF	8
···
 	/* determine FIFO size and enable FIFO mode */
 	temp = readb(sport->port.membase + UARTPFIFO);
 
-	sport->txfifo_size = 0x1 << (((temp >> UARTPFIFO_TXSIZE_OFF) &
-		UARTPFIFO_FIFOSIZE_MASK) + 1);
-
+	sport->txfifo_size = UARTFIFO_DEPTH((temp >> UARTPFIFO_TXSIZE_OFF) &
+					    UARTPFIFO_FIFOSIZE_MASK);
 	sport->port.fifosize = sport->txfifo_size;
 
-	sport->rxfifo_size = 0x1 << (((temp >> UARTPFIFO_RXSIZE_OFF) &
-		UARTPFIFO_FIFOSIZE_MASK) + 1);
+	sport->rxfifo_size = UARTFIFO_DEPTH((temp >> UARTPFIFO_RXSIZE_OFF) &
+					    UARTPFIFO_FIFOSIZE_MASK);
 
 	spin_lock_irqsave(&sport->port.lock, flags);
 
···
 	/* determine FIFO size */
 	temp = lpuart32_read(&sport->port, UARTFIFO);
 
-	sport->txfifo_size = 0x1 << (((temp >> UARTFIFO_TXSIZE_OFF) &
-		UARTFIFO_FIFOSIZE_MASK) - 1);
-
+	sport->txfifo_size = UARTFIFO_DEPTH((temp >> UARTFIFO_TXSIZE_OFF) &
+					    UARTFIFO_FIFOSIZE_MASK);
 	sport->port.fifosize = sport->txfifo_size;
 
-	sport->rxfifo_size = 0x1 << (((temp >> UARTFIFO_RXSIZE_OFF) &
-		UARTFIFO_FIFOSIZE_MASK) - 1);
+	sport->rxfifo_size = UARTFIFO_DEPTH((temp >> UARTFIFO_RXSIZE_OFF) &
+					    UARTFIFO_FIFOSIZE_MASK);
 
 	spin_lock_irqsave(&sport->port.lock, flags);