serial: amba-pl011: Fix RX stall when DMA is used

commit 2bcacc1c87acf9a8ebc17de18cb2b3cfeca547cf upstream.

Function pl011_throttle_rx() calls pl011_stop_rx() to disable RX, which
also disables the RX DMA by clearing the RXDMAE bit of the DMACR
register. However, to properly unthrottle RX when DMA is used, the
function pl011_unthrottle_rx() is expected to set the RXDMAE bit of
the DMACR register, which it currently lacks. This causes RX to stall
after the throttle API is called.

Set RXDMAE bit in the DMACR register while unthrottling RX if RX DMA is
used.

Fixes: 211565b10099 ("serial: pl011: UPSTAT_AUTORTS requires .throttle/unthrottle")
Cc: stable@vger.kernel.org
Signed-off-by: Kartik Rajput <kkartik@nvidia.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20241113092629.60226-1-kkartik@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 8b1644f5411ecf501663852a57145c225714a596..2b93df55fdb28f9867329fd50526950e8679c9a4 100644 (file)
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -1819,6 +1819,11 @@ static void pl011_unthrottle_rx(struct uart_port *port)
 
        pl011_write(uap->im, uap, REG_IMSC);
 
+       if (uap->using_rx_dma) {
+               uap->dmacr |= UART011_RXDMAE;
+               pl011_write(uap->dmacr, uap, REG_DMACR);
+       }
+
        uart_port_unlock_irqrestore(&uap->port, flags);
 }