linux-kernel - [PATCH 1/3] tty: serial: fsl_lpuart: move dev_info

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Date:   Tue, 24 Mar 2020 19:47:56 +0100
From:   Michael Walle <michael@...le.cc>
To:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Jiri Slaby <jslaby@...e.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Walle <michael@...le.cc>,
        Leonard Crestez <leonard.crestez@....com>
Subject: [PATCH 1/3] tty: serial: fsl_lpuart: move dev_info_once()

Don't take the spinlock and use dev_info_once(). This may cause a hang
because the console takes this spinlock, too. Just print this info after
we've released the lock.

Fixes: 159381df1442f ("tty: serial: fsl_lpuart: fix DMA operation when using IOMMU")
Reported-by: Leonard Crestez <leonard.crestez@....com>
Signed-off-by: Michael Walle <michael@...le.cc>
---
 drivers/tty/serial/fsl_lpuart.c | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 9c6a018b1390..960fc2658f19 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1517,9 +1517,6 @@ static void lpuart_tx_dma_startup(struct lpuart_port *sport)
 
 	sport->dma_tx_chan = dma_request_chan(sport->port.dev, "tx");
 	if (IS_ERR(sport->dma_tx_chan)) {
-		dev_info_once(sport->port.dev,
-			      "DMA tx channel request failed, operating without tx DMA (%ld)\n",
-			      PTR_ERR(sport->dma_tx_chan));
 		sport->dma_tx_chan = NULL;
 		goto err;
 	}
@@ -1551,9 +1548,6 @@ static void lpuart_rx_dma_startup(struct lpuart_port *sport)
 
 	sport->dma_rx_chan = dma_request_chan(sport->port.dev, "rx");
 	if (IS_ERR(sport->dma_rx_chan)) {
-		dev_info_once(sport->port.dev,
-			      "DMA rx channel request failed, operating without rx DMA (%ld)\n",
-			      PTR_ERR(sport->dma_rx_chan));
 		sport->dma_rx_chan = NULL;
 		goto err;
 	}
@@ -1601,6 +1595,13 @@ static int lpuart_startup(struct uart_port *port)
 
 	spin_unlock_irqrestore(&sport->port.lock, flags);
 
+	if (!sport->dma_rx_chan)
+		dev_info_once(sport->port.dev,
+			      "DMA rx channel request failed, operating without rx DMA\n");
+	if (!sport->dma_tx_chan)
+		dev_info_once(sport->port.dev,
+			      "DMA tx channel request failed, operating without tx DMA\n");
+
 	return 0;
 }
 
@@ -1653,13 +1654,20 @@ static int lpuart32_startup(struct uart_port *port)
 
 	lpuart32_setup_watermark_enable(sport);
 
-
 	lpuart_rx_dma_startup(sport);
 	lpuart_tx_dma_startup(sport);
 
 	lpuart32_configure(sport);
 
 	spin_unlock_irqrestore(&sport->port.lock, flags);
+
+	if (!sport->dma_rx_chan)
+		dev_info_once(sport->port.dev,
+			      "DMA rx channel request failed, operating without rx DMA\n");
+	if (!sport->dma_tx_chan)
+		dev_info_once(sport->port.dev,
+			      "DMA tx channel request failed, operating without tx DMA\n");
+
 	return 0;
 }
 
-- 
2.20.1