On Thu, Oct 30, 2014 at 04:39:37PM +0000, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
>
> It will be used by other call sites shortly.
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_dma.c | 38 +++++++++++++++++++++++++++++
> drivers/gpu/drm/i915/i915_gem_userptr.c | 43 ++-------------------------------
> drivers/gpu/drm/i915/intel_drv.h | 4 +++
> 3 files changed, 44 insertions(+), 41 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 5b157bb..0b34571 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -2070,3 +2070,41 @@ int i915_driver_device_is_agp(struct drm_device *dev)
> {
> return 1;
> }
> +
> +#if IS_ENABLED(CONFIG_SWIOTLB)
> +#define swiotlb_active() swiotlb_nr_tbl()
> +#else
> +#define swiotlb_active() 0
> +#endif
> +
> +int i915_st_set_pages(struct sg_table **st, struct page **pvec, int num_pages)
> +{
> + struct scatterlist *sg;
> + int ret, n;
> +
> + *st = kmalloc(sizeof(**st), GFP_KERNEL);
> + if (*st == NULL)
> + return -ENOMEM;
> +
> + if (swiotlb_active()) {
> + ret = sg_alloc_table(*st, num_pages, GFP_KERNEL);
> + if (ret)
> + goto err;
> +
> + for_each_sg((*st)->sgl, sg, num_pages, n)
> + sg_set_page(sg, pvec[n], PAGE_SIZE, 0);
> + } else {
> + ret = sg_alloc_table_from_pages(*st, pvec, num_pages,
> + 0, num_pages << PAGE_SHIFT,
> + GFP_KERNEL);
> + if (ret)
> + goto err;
> + }
Ok, I don't really understand why we don't just always use
sg_alloc_table_from_pages undconditionally - if swiotlb _ever_ gets in
between us and the hw, everything will pretty much fall apart.
git blame doesn't shed light on this particular issue. Chris?
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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