linux-kernel - Re: [PATCH] dmaengine: ste_dma40, imx-dma: Cleanup scatterlist layering violations

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Date:   Mon, 29 May 2017 13:26:14 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Logan Gunthorpe <logang@...tatee.com>,
        Per Förlin <per.forlin@...s.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dmaengine@...r.kernel.org, Stephen Bates <sbates@...thlin.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Vinod Koul <vinod.koul@...el.com>
Subject: Re: [PATCH] dmaengine: ste_dma40, imx-dma: Cleanup scatterlist
 layering violations

On Wed, May 24, 2017 at 11:58 PM, Logan Gunthorpe <logang@...tatee.com> wrote:

> Two dma engine drivers directly accesses page_link assuming knowledge
> that should be contained only in scatterlist.h.
>
> We replace these with calls to sg_chain and sg_assign_page.
>
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> Signed-off-by: Stephen Bates <sbates@...thlin.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Vinod Koul <vinod.koul@...el.com>
> Cc: Linus Walleij <linus.walleij@...aro.org>

OMG I guess you know what you're doing, so:
Acked-by: Linus Walleij <linus.walleij@...aro.org>

I will shout if Ux500 breaks.

CC Per Förlin who wrote the code.

>  drivers/dma/imx-dma.c   | 7 ++-----
>  drivers/dma/ste_dma40.c | 5 +----
>  2 files changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
> index ab0fb80..f681df8 100644
> --- a/drivers/dma/imx-dma.c
> +++ b/drivers/dma/imx-dma.c
> @@ -888,7 +888,7 @@ static struct dma_async_tx_descriptor *imxdma_prep_dma_cyclic(
>         sg_init_table(imxdmac->sg_list, periods);
>
>         for (i = 0; i < periods; i++) {
> -               imxdmac->sg_list[i].page_link = 0;
> +               sg_assign_page(&imxdmac->sg_list[i], NULL);
>                 imxdmac->sg_list[i].offset = 0;
>                 imxdmac->sg_list[i].dma_address = dma_addr;
>                 sg_dma_len(&imxdmac->sg_list[i]) = period_len;
> @@ -896,10 +896,7 @@ static struct dma_async_tx_descriptor *imxdma_prep_dma_cyclic(
>         }
>
>         /* close the loop */
> -       imxdmac->sg_list[periods].offset = 0;
> -       sg_dma_len(&imxdmac->sg_list[periods]) = 0;
> -       imxdmac->sg_list[periods].page_link =
> -               ((unsigned long)imxdmac->sg_list | 0x01) & ~0x02;
> +       sg_chain(imxdmac->sg_list, periods + 1, imxdmac->sg_list);
>
>         desc->type = IMXDMA_DESC_CYCLIC;
>         desc->sg = imxdmac->sg_list;
> diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
> index a6620b6..c3052fb 100644
> --- a/drivers/dma/ste_dma40.c
> +++ b/drivers/dma/ste_dma40.c
> @@ -2528,10 +2528,7 @@ dma40_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t dma_addr,
>                 dma_addr += period_len;
>         }
>
> -       sg[periods].offset = 0;
> -       sg_dma_len(&sg[periods]) = 0;
> -       sg[periods].page_link =
> -               ((unsigned long)sg | 0x01) & ~0x02;
> +       sg_chain(sg, periods + 1, sg);
>
>         txd = d40_prep_sg(chan, sg, sg, periods, direction,
>                           DMA_PREP_INTERRUPT);
> --
> 2.1.4
>