Re: [Intel-gfx] [RFC 5/7] drm/i915: Use i915_sg_create for dmabuf

[Tvrtko Ursulin]

On 13/10/2016 10:15, Chris Wilson wrote:

On Thu, Oct 13, 2016 at 10:04:02AM +0100, Tvrtko Ursulin wrote:

-   src = obj->pages->sgl;
-   dst = st->sgl;
-   for (i = 0; i < obj->pages->nents; i++) {
-   sg_set_page(dst, sg_page(src), src->length, 0);
-   dst = sg_next(dst);
-   src = sg_next(src);
-   }
+   for_each_sgt_page(page, sgt_iter, obj->pages)
+   i915_sg_add_page(state, page);

This (and partial_pages) can just copy the existing compact obj->pages.
The previous code should already be as compact as its input. And that is
not a simpler loop!


Ah yes, you are right. A bit too mindless "search and replace" on my part.

Regards,

Tvrtko

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Re: [Intel-gfx] [RFC 5/7] drm/i915: Use i915_sg_create for dmabuf

[Chris Wilson]

On Thu, Oct 13, 2016 at 10:04:02AM +0100, Tvrtko Ursulin wrote:
> - src = obj->pages->sgl;
> - dst = st->sgl;
> - for (i = 0; i < obj->pages->nents; i++) {
> - sg_set_page(dst, sg_page(src), src->length, 0);
> - dst = sg_next(dst);
> - src = sg_next(src);
> - }
> + for_each_sgt_page(page, sgt_iter, obj->pages)
> + i915_sg_add_page(state, page);

This (and partial_pages) can just copy the existing compact obj->pages.
The previous code should already be as compact as its input. And that is
not a simpler loop!
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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[Intel-gfx] [RFC 5/7] drm/i915: Use i915_sg_create for dmabuf

[Tvrtko Ursulin]

From: Tvrtko Ursulin 

As for the earlier ones, it simplifies the loop and
enables entry colaescing.

Signed-off-by: Tvrtko Ursulin 
---
 drivers/gpu/drm/i915/i915_gem_dmabuf.c | 45 +++---
 1 file changed, 20 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c 
b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
index 97c9d68b45df..5df1dfdeec66 100644
--- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
@@ -40,11 +40,13 @@ static struct sg_table *i915_gem_map_dma_buf(struct 
dma_buf_attachment *attachme
 enum dma_data_direction dir)
 {
struct drm_i915_gem_object *obj = dma_buf_to_obj(attachment->dmabuf);
-   struct sg_table *st;
-   struct scatterlist *src, *dst;
-   int ret, i;
+   struct drm_device *dev = obj->base.dev;
+   struct i915_sg_create_state *state;
+   struct sgt_iter sgt_iter;
+   struct page *page;
+   int ret;
 
-   ret = i915_mutex_lock_interruptible(obj->base.dev);
+   ret = i915_mutex_lock_interruptible(dev);
if (ret)
goto err;
 
@@ -55,40 +57,33 @@ static struct sg_table *i915_gem_map_dma_buf(struct 
dma_buf_attachment *attachme
i915_gem_object_pin_pages(obj);
 
/* Copy sg so that we make an independent mapping */
-   st = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
-   if (st == NULL) {
-   ret = -ENOMEM;
+   state = i915_sg_create(obj->pages->nents);
+   if (IS_ERR(state)) {
+   ret = PTR_ERR(state);
goto err_unpin;
}
 
-   ret = sg_alloc_table(st, obj->pages->nents, GFP_KERNEL);
-   if (ret)
-   goto err_free;
-
-   src = obj->pages->sgl;
-   dst = st->sgl;
-   for (i = 0; i < obj->pages->nents; i++) {
-   sg_set_page(dst, sg_page(src), src->length, 0);
-   dst = sg_next(dst);
-   src = sg_next(src);
-   }
+   for_each_sgt_page(page, sgt_iter, obj->pages)
+   i915_sg_add_page(state, page);
 
-   if (!dma_map_sg(attachment->dev, st->sgl, st->nents, dir)) {
+   i915_sg_complete(state);
+
+   if (!dma_map_sg(attachment->dev,
+   state->st->sgl, state->st->nents, dir)) {
ret =-ENOMEM;
goto err_free_sg;
}
 
-   mutex_unlock(>base.dev->struct_mutex);
-   return st;
+   mutex_unlock(>struct_mutex);
+
+   return state->st;
 
 err_free_sg:
-   sg_free_table(st);
-err_free:
-   kfree(st);
+   i915_sg_abort(state);
 err_unpin:
i915_gem_object_unpin_pages(obj);
 err_unlock:
-   mutex_unlock(>base.dev->struct_mutex);
+   mutex_unlock(>struct_mutex);
 err:
return ERR_PTR(ret);
 }
-- 
2.7.4

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