serial: uartps: Add a timeout to the tx empty wait

#include <linux/of.h>

#include <linux/module.h>

#include <linux/pm_runtime.h>

#include <linux/iopoll.h>

#define CDNS_UART_TTY_NAME	"ttyPS"

#define CDNS_UART_NAME		"xuartps"

#define CDNS_UART_MAJOR		0	/* use dynamic node allocation */

#define CDNS_UART_FIFO_SIZE	64	/* FIFO size */

#define CDNS_UART_REGISTER_SPACE	0x1000

#define TX_TIMEOUT		500000

/* Rx Trigger level */

static int rx_trigger_level = 56;

	unsigned int cval = 0;

	unsigned int baud, minbaud, maxbaud;

	unsigned long flags;

	unsigned int ctrl_reg, mode_reg;

	unsigned int ctrl_reg, mode_reg, val;

	int err;

	/* Wait for the transmit FIFO to empty before making changes */

	if (!(readl(port->membase + CDNS_UART_CR) &

				CDNS_UART_CR_TX_DIS)) {

		while (!(readl(port->membase + CDNS_UART_SR) &

				CDNS_UART_SR_TXEMPTY)) {

			cpu_relax();

		err = readl_poll_timeout(port->membase + CDNS_UART_SR,

					 val, (val & CDNS_UART_SR_TXEMPTY),

					 1000, TX_TIMEOUT);

		if (err) {

			dev_err(port->dev, "timed out waiting for tx empty");

			return;

		}

	}

	spin_lock_irqsave(&port->lock, flags);