serial: 8250: Flush DMA Rx on RLSI

stable inclusion
from stable-v5.10.156
commit 8679087e93574742d7cceb001d7a1bd558585395
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7MCG1

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8679087e93574742d7cceb001d7a1bd558585395

--------------------------------

commit 1980860e upstream.

Returning true from handle_rx_dma() without flushing DMA first creates
a data ordering hazard. If DMA Rx has handled any character at the
point when RLSI occurs, the non-DMA path handles any pending characters
jumping them ahead of those characters that are pending under DMA.

Fixes: 75df022b ("serial: 8250_dma: Fix RX handling")
Cc: <stable@vger.kernel.org>
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20221108121952.5497-5-ilpo.jarvinen@linux.intel.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Nsanglipeng <sanglipeng1@jd.com>
(cherry picked from commit 09892a07)

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

@@ -1873,10 +1873,9 @@ static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
 		if (!up->dma->rx_running)
 			break;
 		fallthrough;
+	case UART_IIR_RLSI:
 	case UART_IIR_RX_TIMEOUT:
 		serial8250_rx_dma_flush(up);
-		fallthrough;
-	case UART_IIR_RLSI:
 		return true;
 	}
 	return up->dma->rx_dma(up);