linux-kernel - RE: [PATCH V2] tty: serial: fsl_lpuart: use the sg count from dma_map

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Date:   Thu, 7 Nov 2019 06:36:52 +0000
From:   Peng Fan <peng.fan@....com>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "jslaby@...e.com" <jslaby@...e.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "festevam@...il.com" <festevam@...il.com>
CC:     dl-linux-imx <linux-imx@....com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andy Duan <fugang.duan@....com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH V2] tty: serial: fsl_lpuart: use the sg count from
 dma_map_sg

> Subject: [PATCH V2] tty: serial: fsl_lpuart: use the sg count from dma_map_sg

Ignore this patch. Keep v1.

Thanks,
Peng.

> 
> From: Peng Fan <peng.fan@....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@...r.kernel.org>
> Signed-off-by: Peng Fan <peng.fan@....com>
> ---
> 
> 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 this
>   is ok for you, or you need I have a follow up fix for v1.
> 
>  drivers/tty/serial/fsl_lpuart.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.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;
>  	}
> 
> +	sport->dma_tx_nents = ret;
>  	sport->dma_tx_desc = dmaengine_prep_slave_sg(sport->dma_tx_chan,
> sgl,
>  					sport->dma_tx_nents,
>  					DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT);
> --
> 2.16.4