serial: amba-pl011: Fix RX stall when DMA is used
authorKartik Rajput <kkartik@nvidia.com>
Wed, 13 Nov 2024 09:26:29 +0000 (14:56 +0530)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 13 Nov 2024 14:13:03 +0000 (15:13 +0100)
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>
drivers/tty/serial/amba-pl011.c

index 56e587b94823513ecfb676fa08fe289904258916..2facdbcd73eb160d38c9a2e467c0bf2c6d64d6ac 100644 (file)
@@ -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);
 }