linux-kernel - [PATCH AUTOSEL 5.10 09/93] serial: fsl_lpuart: disable DMA for console and fix sysrq

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Message-Id: <20210710022428.3169839-9-sashal@kernel.org>
Date:   Fri,  9 Jul 2021 22:23:03 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Michael Walle <michael@...le.cc>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>, linux-serial@...r.kernel.org
Subject: [PATCH AUTOSEL 5.10 09/93] serial: fsl_lpuart: disable DMA for console and fix sysrq

From: Michael Walle <michael@...le.cc>

[ Upstream commit 8cac2f6eb8548245e6f8fb893fc7f2a714952654 ]

SYSRQ doesn't work with DMA. This is because there is no error
indication whether a symbol had a framing error or not. Actually,
this is not completely correct, there is a bit in the data register
which is set in this case, but we'd have to read change the DMA access
to 16 bit and we'd need to post process the data, thus make the DMA
pointless in the first place.

Signed-off-by: Michael Walle <michael@...le.cc>
Link: https://lore.kernel.org/r/20210512141255.18277-10-michael@walle.cc
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/serial/fsl_lpuart.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 7aab87c92192..996e9aaa243e 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1581,6 +1581,9 @@ static void lpuart_tx_dma_startup(struct lpuart_port *sport)
 	u32 uartbaud;
 	int ret;
 
+	if (uart_console(&sport->port))
+		goto err;
+
 	if (!sport->dma_tx_chan)
 		goto err;
 
@@ -1610,6 +1613,9 @@ static void lpuart_rx_dma_startup(struct lpuart_port *sport)
 	int ret;
 	unsigned char cr3;
 
+	if (uart_console(&sport->port))
+		goto err;
+
 	if (!sport->dma_rx_chan)
 		goto err;
 
-- 
2.30.2