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From:   Peng Fan <peng.fan@nxp.com>
To:     "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "jslaby@suse.com" <jslaby@suse.com>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
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CC:     dl-linux-imx <linux-imx@nxp.com>,
        "linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Peng Fan <peng.fan@nxp.com>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: [PATCH] tty: serial: fsl_lpuart: use the sg count from dma_map_sg
Thread-Topic: [PATCH] tty: serial: fsl_lpuart: use the sg count from
 dma_map_sg
Thread-Index: AQHVk50GWgKPiRrVwUSj/ElNagRx2g==
Date:   Tue, 5 Nov 2019 05:51:10 +0000
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From: Peng Fan <peng.fan@nxp.com>

The dmaengine_prep_slave_sg needs to use sg count returned
by dma_map_sg, not use sport->dma_tx_nents, because the return
value of dma_map_sg is not always same with "nents".

When enabling iommu for lpuart + edma, iommu framework may concatenate
two sgs into one.

Fixes: 6250cc30c4c4e ("tty: serial: fsl_lpuart: Use scatter/gather DMA for =
Tx")
Cc: <stable@vger.kernel.org>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
---
 drivers/tty/serial/fsl_lpuart.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuar=
t.c
index 3e17bb8a0b16..3643b8f7a3df 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -437,8 +437,8 @@ static void lpuart_dma_tx(struct lpuart_port *sport)
 	}
=20
 	sport->dma_tx_desc =3D dmaengine_prep_slave_sg(sport->dma_tx_chan, sgl,
-					sport->dma_tx_nents,
-					DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT);
+					ret, DMA_MEM_TO_DEV,
+					DMA_PREP_INTERRUPT);
 	if (!sport->dma_tx_desc) {
 		dma_unmap_sg(dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);
 		dev_err(dev, "Cannot prepare TX slave DMA!\n");
--=20
2.16.4