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

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 2d42f485c987669280c692b71be8b440fe1aa17f..7d99bc3be0b83ea1824a2111c56b3e43da4e0282 100644 (file)
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -1298,10 +1298,12 @@ 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) {