Revert "serial: 8250: 8250_omap: Fix possible interrupt storm"

This reverts commit 31fae7c8.

Tony writes:
	I just noticed this causes the following regression in Linux
	next when pressing a key on uart console after boot at least on
	omap3. This seems to happen on serial_port_in(port, UART_RX) in
	the quirk handling.

So let's drop this.

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/YLCCJzkkB4N7LTQS@atomide.com
Fixes: 31fae7c8 ("serial: 8250: 8250_omap: Fix possible interrupt storm")
Reported-by: Tony Lindgren <tony@atomide.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_omap.c

@@ -104,9 +104,6 @@
 #define UART_OMAP_EFR2			0x23
 #define UART_OMAP_EFR2_TIMEOUT_BEHAVE	BIT(6)
 
-/* RX FIFO occupancy indicator */
-#define UART_OMAP_RX_LVL		0x64
-
 struct omap8250_priv {
 	int line;
 	u8 habit;
@@ -628,15 +625,6 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
 	serial8250_rpm_get(up);
 	iir = serial_port_in(port, UART_IIR);
 	ret = serial8250_handle_irq(port, iir);
-	/*
-	 * It is possible that RX TIMEOUT is signalled after FIFO
-	 * has been drained, in which case a dummy read of RX FIFO is
-	 * required to clear RX TIMEOUT condition.
-	 */
-	if ((iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT) {
-		if (serial_port_in(port, UART_OMAP_RX_LVL) == 0)
-			serial_port_in(port, UART_RX);
-	}
 	serial8250_rpm_put(up);
 
 	return IRQ_RETVAL(ret);