cadence: Change logic in uart driver

Write char if fifo is empty. If this is done like this all chars are
printed. Because origin code just put that chars to fifo and in case of
reset messages were missing.

Before this change chars are put to fifo and only check before adding if
fifo is full. The patch is changing this logic that it is adding char only
when fifo is empty to make sure that in case of reset (by another SW for
example) all chars are printed. Maybe one char can be missed but for IP
itself it is much easier to send just one char compare to full fifo.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Change-Id: Ic24c2c1252bce24be2aed68ee29477ca4a549e5f

drivers/cadence/uart/aarch64/cdns_console.S

@@ -105,15 +105,15 @@ func console_cdns_core_putc
 	cmp	w0, #0xA
 	b.ne	2f
 1:
-	/* Check if the transmit FIFO is full */
+	/* Check if the transmit FIFO is empty */
 	ldr	w2, [x1, #R_UART_SR]
-	tbnz	w2, #UART_SR_INTR_TFUL_BIT, 1b
+	tbz	w2, #UART_SR_INTR_TEMPTY_BIT, 1b
 	mov	w2, #0xD
 	str	w2, [x1, #R_UART_TX]
 2:
-	/* Check if the transmit FIFO is full */
+	/* Check if the transmit FIFO is empty */
 	ldr	w2, [x1, #R_UART_SR]
-	tbnz	w2, #UART_SR_INTR_TFUL_BIT, 2b
+	tbz	w2, #UART_SR_INTR_TEMPTY_BIT, 2b
 	str	w0, [x1, #R_UART_TX]
 	ret
 endfunc console_cdns_core_putc

include/drivers/cadence/cdns_uart.h

@@ -21,6 +21,7 @@
 #define R_UART_SR		0x2C
 #define UART_SR_INTR_REMPTY_BIT	1
 #define UART_SR_INTR_TFUL_BIT	4
+#define UART_SR_INTR_TEMPTY_BIT	3
 
 #define R_UART_TX	0x30
 #define R_UART_RX	0x30