Re: [PATCH v2] dmaengine: qcom_hidma: Remove useless DMA-32 fallback configuration

[Christophe JAILLET]

Le 22/01/2022 à 19:05, Sinan Kaya a écrit :
> On 1/15/2022 2:35 AM, Christophe JAILLET wrote:
> > As stated in [1], dma_set_mask() with a 64-bit mask never fails if
> > dev->dma_mask is non-NULL.
> > So, if it fails, the 32 bits case will also fail for the same reason.
> >
> > Simplify code and remove some dead code accordingly.
> >
> > [1]: 
> > https://lore.kernel.org/linux-kernel/YL3vSPK5DXTNvgdx@xxxxxxxxxxxxx/#t
>
> Can we please document this?

Hi, the patch has been applied, but [1] is sometimes given as an 
explanation link.

CJ


[1]: 
https://lists.linuxfoundation.org/pipermail/iommu/2019-February/033674.html

> Usual practice was to try allocating 64 bit DMA if possible and fallback
> to 32 bits.
>
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> > ---
> > v2: have the subject and updated driver match
> > ---
> >   drivers/dma/qcom/hidma.c | 4 +---
> >   1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/drivers/dma/qcom/hidma.c b/drivers/dma/qcom/hidma.c
> > index 65d054bb11aa..51587cf8196b 100644
> > --- a/drivers/dma/qcom/hidma.c
> > +++ b/drivers/dma/qcom/hidma.c
> > @@ -838,9 +838,7 @@ static int hidma_probe(struct platform_device *pdev)
> >       rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
> >       if (rc) {
> >           dev_warn(&pdev->dev, "unable to set coherent mask to 64");
> > -        rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> > -        if (rc)
> > -            goto dmafree;
> > +        goto dmafree;
> >       }
> >       dmadev->lldev = hidma_ll_init(dmadev->ddev.dev,