Revert "OMAP: UART: Keep the TX fifo full when possible"

This reverts commit c441508421.

Kevin writes:
	Hmm, another OMAP serial patch that wasn't Cc'd to linux-omap
	where OMAP users might have seen it. :(

	I just bisected a strange problem in linux-next on OMAP3 down to
	this patch.  Reverting it fixes the problem.

	On OMAP3530 Beagle and Overo, after boot, doing a 'cat
	/proc/cpuinfo' was not returning to a prompt, suggesting
	something strange with the FIFO.  Hitting return gets me back to
	a prompt.

	Greg, this one should also be dropped from tty-next until it can
	be further investgated and the problem solved.

Reported-by: Kevin Hilman <khilman@linaro.org>
Cc: Dmitry Fink <finik@ti.com>
Cc: Alexander Savchenko <oleksandr.savchenko@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/omap-serial.c

@@ -350,8 +350,7 @@ static void transmit_chars(struct uart_omap_port *up, unsigned int lsr)
 		serial_omap_stop_tx(&up->port);
 		return;
 	}
-	count = up->port.fifosize -
-		(serial_in(up, UART_OMAP_TXFIFO_LVL) & 0xFF);
+	count = up->port.fifosize / 4;
 	do {
 		serial_out(up, UART_TX, xmit->buf[xmit->tail]);
 		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);

include/uapi/linux/serial_reg.h

@@ -366,7 +366,6 @@
 #define UART_OMAP_MDR1_FIR_MODE		0x05	/* FIR mode */
 #define UART_OMAP_MDR1_CIR_MODE		0x06	/* CIR mode */
 #define UART_OMAP_MDR1_DISABLE		0x07	/* Disable (default state) */
-#define UART_OMAP_TXFIFO_LVL		0x1A	/* TX FIFO fullness */
 
 /*
  * These are definitions for the Exar XR17V35X and XR17(C|D)15X