serial: 8250: 8250_omap: Do not start RX DMA on THRI interrupt

commit c6bb057418876cdfdd29a6f7b8cef54539ee8811 upstream.

Starting RX DMA on THRI interrupt is too early because TX may not have
finished yet.

This change is inspired by commit 90b8596ac460 ("serial: 8250: Prevent
starting up DMA Rx on THRI interrupt") and fixes DMA issues I had with
an AM62 SoC that is using the 8250 OMAP variant.

Cc: stable@vger.kernel.org
Fixes: c26389f998a8 ("serial: 8250: 8250_omap: Add DMA support for UARTs on K3 SoCs")
Signed-off-by: Ronald Wahl <ronald.wahl@raritan.com>
Reviewed-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20231101171431.16495-1-rwahl@gmx.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index 66b7b87..0b04d81 100644 (file)
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -1186,10 +1186,12 @@ static int omap_8250_dma_handle_irq(struct uart_port *port)
 
        status = serial_port_in(port, UART_LSR);
 
-       if (priv->habit & UART_HAS_EFR2)
-               am654_8250_handle_rx_dma(up, iir, status);
-       else
-               status = omap_8250_handle_rx_dma(up, iir, status);
+       if ((iir & 0x3f) != UART_IIR_THRI) {
+               if (priv->habit & UART_HAS_EFR2)
+                       am654_8250_handle_rx_dma(up, iir, status);
+               else
+                       status = omap_8250_handle_rx_dma(up, iir, status);
+       }
 
        serial8250_modem_status(up);
        if (status & UART_LSR_THRE && up->dma->tx_err) {