Re: [PATCH v4 3/3] drm/radeon: fix scatter-gather mapping with user pages

[Shane Francis]

> >-----Original Message-----
> >From: dri-devel <dri-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
> >Shane Francis
> >Sent: Wednesday, March 25, 2020 5:08 AM
> >To: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> >Cc: airlied@xxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; bigbeeshane@xxxxxxxxx;
> >amd-gfx-request@xxxxxxxxxxxxxxxxxxxxx; alexander.deucher@xxxxxxx;
> >christian.koenig@xxxxxxx
> >Subject: [PATCH v4 3/3] drm/radeon: fix scatter-gather mapping with user
> >pages
> >
> >Calls to dma_map_sg may return segments / entries than requested
>
> "may return less segment..." ?
>                        ^^^

I will reword / fix the highlighted issues with the text and send a updated
patch set later today.

>
> >if they fall on page bounderies. The old implementation did not
> >support this use case.
> >
> >Signed-off-by: Shane Francis <bigbeeshane@xxxxxxxxx>
> >---
> > drivers/gpu/drm/radeon/radeon_ttm.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c
> >b/drivers/gpu/drm/radeon/radeon_ttm.c
> >index 3b92311d30b9..b3380ffab4c2 100644
> >--- a/drivers/gpu/drm/radeon/radeon_ttm.c
> >+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
> >@@ -528,7 +528,7 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt
> >*ttm)
> >
> >       r = -ENOMEM;
> >       nents = dma_map_sg(rdev->dev, ttm->sg->sgl, ttm->sg->nents,
> >direction);
> >-      if (nents != ttm->sg->nents)
> >+      if (nents == 0)
> >               goto release_sg;
>
> This looks correct to me.
>
> Reviewed-by: Michael J. Ruhl <michael.j.ruhl@xxxxxxxxx>
>
> M
> >       drm_prime_sg_to_page_addr_arrays(ttm->sg, ttm->pages,
> >--
> >2.26.0
> >
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