serial: 8250: Revert "tty: serial: 8250_core: read only RX if there is something...

This reverts commit 0aa525d11859c1a4d5b78fdc704148e2ae03ae13.

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: 0aa525d11859 ("tty: serial: 8250_core: read only RX if there is
something in the FIFO")
Reported-By: Nicolas Schichan <nschichan@freebox.fr>
Debuged-By: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index e3b9570a1eff8aa467ec7dabbe93369c47940e87..deae122c9c4bac6a2bb28d6bbc191bfc18d16747 100644 (file)
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -2138,8 +2138,8 @@ 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_RX);
+       serial_port_in(port, UART_LSR);
+       serial_port_in(port, UART_RX);
        serial_port_in(port, UART_IIR);
        serial_port_in(port, UART_MSR);
 
@@ -2300,8 +2300,8 @@ 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_RX);
+       serial_port_in(port, UART_LSR);
+       serial_port_in(port, UART_RX);
        serial_port_in(port, UART_IIR);
        serial_port_in(port, UART_MSR);
        up->lsr_saved_flags = 0;
@@ -2394,8 +2394,7 @@ 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);
+       serial_port_in(port, UART_RX);
        serial8250_rpm_put(up);
 
        del_timer_sync(&up->timer);