Subject: patch "Revert "serial: 8250: Don't service RX FIFO if interrupts are" added to tty-testing
To:     o.barta89@gmail.com, andriy.shevchenko@linux.intel.com,
        gregkh@linuxfoundation.org, stable@vger.kernel.org
From:   <gregkh@linuxfoundation.org>
Date:   Fri, 21 Jun 2019 11:15:12 +0200
Message-ID: <156110851224136@kroah.com>
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This is a note to let you know that I've just added the patch titled

    Revert "serial: 8250: Don't service RX FIFO if interrupts are

to my tty git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-testing branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will be merged to the tty-next branch sometime soon,
after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.


From 3f2640ed7be838c3f05c0d2b0f7c7508e7431e48 Mon Sep 17 00:00:00 2001
From: Oliver Barta <o.barta89@gmail.com>
Date: Wed, 19 Jun 2019 10:16:39 +0200
Subject: Revert "serial: 8250: Don't service RX FIFO if interrupts are
 disabled"

This reverts commit 2e9fe539108320820016f78ca7704a7342788380.

Reading LSR unconditionally but processing the error flags only if
UART_IIR_RDI bit was set before in IIR may lead to a loss of transmission
error information on UARTs where the transmission error flags are cleared
by a read of LSR. Information are lost in case an error is detected right
before the read of LSR while processing e.g. an UART_IIR_THRI interrupt.

Signed-off-by: Oliver Barta <o.barta89@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Fixes: 2e9fe5391083 ("serial: 8250: Don't service RX FIFO if interrupts are disabled")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/8250/8250_port.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index a6fabc7e3b13..c1cec808571b 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1867,8 +1867,7 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 
 	status = serial_port_in(port, UART_LSR);
 
-	if (status & (UART_LSR_DR | UART_LSR_BI) &&
-	    iir & UART_IIR_RDI) {
+	if (status & (UART_LSR_DR | UART_LSR_BI)) {
 		if (!up->dma || handle_rx_dma(up, iir))
 			status = serial8250_rx_chars(up, status);
 	}
-- 
2.22.0