Re: [PATCH v2] mmc: renesas_sdhi_internal_dmac: set scatter/gather max segment size

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Hi Niklas,

Thanks for your patch!

On Thu, Aug 30, 2018 at 11:39 PM Niklas Söderlund
<niklas.soderlund+renesas@xxxxxxxxxxxx> wrote:
> Fix warning when running with CONFIG_DMA_API_DEBUG_SG=y by allocating a
> device_dma_parameters structure and filling in the max segment size. The
> size used is the result of a discussion with Renesas hardware engineers
> and unfortunately not found in the datasheet.
>
>   renesas_sdhi_internal_dmac ee140000.sd: DMA-API: mapping sg segment
>   longer than device claims to support [len=126976] [max=65536A]

Bogus trailing "A".

> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
> Reported-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
>
> ---
>
> * Changes since v1
> - Use devm_kzalloc() instead of a custom remove function to clean up.
> ---
>  drivers/mmc/host/renesas_sdhi_internal_dmac.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/mmc/host/renesas_sdhi_internal_dmac.c b/drivers/mmc/host/renesas_sdhi_internal_dmac.c
> index c9dab9ce1ed55174..715e0c5dc30e4ebf 100644
> --- a/drivers/mmc/host/renesas_sdhi_internal_dmac.c
> +++ b/drivers/mmc/host/renesas_sdhi_internal_dmac.c
> @@ -308,12 +308,23 @@ static const struct soc_device_attribute gen3_soc_whitelist[] = {
>  static int renesas_sdhi_internal_dmac_probe(struct platform_device *pdev)
>  {
>         const struct soc_device_attribute *soc = soc_device_match(gen3_soc_whitelist);
> +       struct device *dev = &pdev->dev;
>
>         if (!soc)
>                 return -ENODEV;
>
>         global_flags |= (unsigned long)soc->data;
>
> +       if (!dev->dma_parms) {

I guess dev->dma_parms is retained on unbind/rebind?

> +               dev->dma_parms = devm_kzalloc(dev, sizeof(*dev->dma_parms),
> +                                             GFP_KERNEL);

But by using devm_kzalloc(), the memory will be freed, and lead to reuse after
free?

> +               if (!dev->dma_parms)
> +                       return -ENOMEM;
> +       }
> +
> +       if (dma_set_max_seg_size(dev, 0xffffffff))
> +               dev_warn(dev, "Unable to set seg size\n");
> +
>         return renesas_sdhi_probe(pdev, &renesas_sdhi_internal_dmac_dma_ops);
>  }

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds



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