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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>,
        "festevam@gmail.com" <festevam@gmail.com>
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>,
        Andy Duan <fugang.duan@nxp.com>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [PATCH V2] tty: serial: fsl_lpuart: use the sg count from
 dma_map_sg
Thread-Topic: [PATCH V2] tty: serial: fsl_lpuart: use the sg count from
 dma_map_sg
Thread-Index: AQHVlRYSjb10LGdSBU+AJ5B7rW7xA6d/QS9A
Date:   Thu, 7 Nov 2019 06:36:52 +0000
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> Subject: [PATCH V2] tty: serial: fsl_lpuart: use the sg count from dma_ma=
p_sg

Ignore this patch. Keep v1.

Thanks,
Peng.

>=20
> From: Peng Fan <peng.fan@nxp.com>
>=20
> 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".
>=20
> When enabling iommu for lpuart + edma, iommu framework may concatenate
> two sgs into one.
>=20
> Fixes: 6250cc30c4c4e ("tty: serial: fsl_lpuart: Use scatter/gather DMA fo=
r Tx")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
>=20
> V2:
>  Assign ret to sport->dma_tx_nents, then we no need to fix dma_unmap_sg
> Hi Greg,
>   I saw v1 patch merged to tty-next, please help to replace with V2 if th=
is
>   is ok for you, or you need I have a follow up fix for v1.
>=20
>  drivers/tty/serial/fsl_lpuart.c | 1 +
>  1 file changed, 1 insertion(+)
>=20
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpu=
art.c index
> 3e17bb8a0b16..ec5ea098669e 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -436,6 +436,7 @@ static void lpuart_dma_tx(struct lpuart_port *sport)
>  		return;
>  	}
>=20
> +	sport->dma_tx_nents =3D ret;
>  	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);
> --
> 2.16.4