From 2bcacc1c87acf9a8ebc17de18cb2b3cfeca547cf Mon Sep 17 00:00:00 2001
From: Kartik Rajput <kkartik@nvidia.com>
Date: Wed, 13 Nov 2024 14:56:29 +0530
Subject: [PATCH] serial: amba-pl011: Fix RX stall when DMA is used
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 | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 56e587b948235..2facdbcd73eb1 100644
--- 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);
}
--
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