Commit 3f2640ed authored Jun 19, 2019 by Oliver Barta Committed by Greg Kroah-Hartman Jun 21, 2019

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

This reverts commit 2e9fe539.

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: 2e9fe539 ("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>

parent 4a96895f

drivers/tty/serial/8250/8250_port.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -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);
		}

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