[PATCH 2/2] drm/amdgpu: Allow dma_map_sg() coalescing

[Christian König]

Am 11.04.2018 um 19:11 schrieb Robin Murphy:
> Now that drm_prime_sg_to_page_addr_arrays() understands the case where
> dma_map_sg() has coalesced segments and returns 0 < count < nents, we
> can relax the check to only consider genuine failure.

That pattern is repeated in pretty much all drivers using TTM.

So you would need to fix all of them, but as I said I don't think that 
this approach is a good idea.

We essentially wanted to get rid of the dma_address array in the mid 
term and that change goes into the exactly opposite direction.

Regards,
Christian.

>
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index 205da3ff9cd0..f81e96a4242f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -813,7 +813,7 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm)
>   
>   	r = -ENOMEM;
>   	nents = dma_map_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction);
> -	if (nents != ttm->sg->nents)
> +	if (nents == 0)
>   		goto release_sg;
>   
>   	drm_prime_sg_to_page_addr_arrays(ttm->sg, ttm->pages,