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Subject[PATCH 5.1 110/138] Revert "serial: 8250: Dont service RX FIFO if interrupts are disabled"
Date
From: Oliver Barta <o.barta89@gmail.com>

commit 3f2640ed7be838c3f05c0d2b0f7c7508e7431e48 upstream.

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(-)

--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1869,8 +1869,7 @@ int serial8250_handle_irq(struct uart_po

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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