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Commit d2d74ad4 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Sasha Levin
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serial: 8250: Revert "tty: serial: 8250_core: read only RX if there is something in the FIFO" 



commit ca8bb4aefb932e3da105f28cbfba36d57a931081 upstream.

This reverts commit 0aa525d1.

The conditional RX-FIFO read seems to cause spurious interrupts and we
see just:
|serial8250: too much work for irq29

The previous behaviour was "default" for decades and Marvell's 88f6282 SoC
might not be the only that relies on it. Therefore the Omap fix is
reverted for now.

Fixes: 0aa525d1 ("tty: serial: 8250_core: read only RX if there is
something in the FIFO")
Reported-By: default avatarNicolas Schichan <nschichan@freebox.fr>
Debuged-By: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
parent 8ca9d129

drivers/tty/serial/8250/8250_core.c

+5 −6
Original line number Diff line number Diff line
@@ -2088,7 +2088,7 @@ int serial8250_do_startup(struct uart_port *port) 
	/*

	 * Clear the interrupt registers.

	 */

	if (serial_port_in(port, UART_LSR) & UART_LSR_DR)

	serial_port_in(port, UART_LSR);

	serial_port_in(port, UART_RX);

	serial_port_in(port, UART_IIR);

	serial_port_in(port, UART_MSR);
@@ -2250,7 +2250,7 @@ dont_test_tx_en: 
	 * saved flags to avoid getting false values from polling

	 * routines or the previous session.

	 */

	if (serial_port_in(port, UART_LSR) & UART_LSR_DR)

	serial_port_in(port, UART_LSR);

	serial_port_in(port, UART_RX);

	serial_port_in(port, UART_IIR);

	serial_port_in(port, UART_MSR);
@@ -2344,7 +2344,6 @@ void serial8250_do_shutdown(struct uart_port *port) 
	 * Read data port to reset things, and then unlink from

	 * the IRQ chain.

	 */

	if (serial_port_in(port, UART_LSR) & UART_LSR_DR)

	serial_port_in(port, UART_RX);

	serial8250_rpm_put(up);