drm/i915: handle walking compact dma scatter lists

So far the assumption was that each dma scatter list entry contains only
a single page. This might not hold in the future, when we'll introduce
compact scatter lists, so prepare for this everywhere in the i915 code
where we walk such a list.

We'll fix the place _creating_ these lists separately in the next patch
to help the reviewing/bisectability.

Reference: http://www.spinics.net/lists/dri-devel/msg33917.html
Signed-off-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

4 files changed, 31 insertions, 41 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 71f285c56f1e..1246a31c0243 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1528,17 +1528,12 @@ void i915_gem_lastclose(struct drm_device *dev);
 int __must_check i915_gem_object_get_pages(struct drm_i915_gem_object *obj);
 static inline struct page *i915_gem_object_get_page(struct drm_i915_gem_object *obj, int n)
 {
-        struct scatterlist *sg = obj->pages->sgl;
-        int nents = obj->pages->nents;
-        while (nents > SG_MAX_SINGLE_ALLOC) {
-                if (n < SG_MAX_SINGLE_ALLOC - 1)
-                        break;
-
-                sg = sg_chain_ptr(sg + SG_MAX_SINGLE_ALLOC - 1);
-                n -= SG_MAX_SINGLE_ALLOC - 1;
-                nents -= SG_MAX_SINGLE_ALLOC - 1;
-        }
-        return sg_page(sg+n);
+        struct sg_page_iter sg_iter;
+
+        for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, n)
+                return sg_iter.page;
+
+        return NULL;
 }
 static inline void i915_gem_object_pin_pages(struct drm_i915_gem_object *obj)
 {
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 30117dc52212..5cf6140354db 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -411,8 +411,7 @@ i915_gem_shmem_pread(struct drm_device *dev,
         int obj_do_bit17_swizzling, page_do_bit17_swizzling;
         int prefaulted = 0;
         int needs_clflush = 0;
-        struct scatterlist *sg;
-        int i;
+        struct sg_page_iter sg_iter;
 
         user_data = to_user_ptr(args->data_ptr);
         remain = args->size;
@@ -441,11 +440,9 @@ i915_gem_shmem_pread(struct drm_device *dev,
 
         offset = args->offset;
 
-        for_each_sg(obj->pages->sgl, sg, obj->pages->nents, i) {
-                struct page *page;
-
-                if (i < offset >> PAGE_SHIFT)
-                        continue;
+        for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents,
+                         offset >> PAGE_SHIFT) {
+                struct page *page = sg_iter.page;
 
                 if (remain <= 0)
                         break;
@@ -460,7 +457,6 @@ i915_gem_shmem_pread(struct drm_device *dev,
                 if ((shmem_page_offset + page_length) > PAGE_SIZE)
                         page_length = PAGE_SIZE - shmem_page_offset;
 
-                page = sg_page(sg);
                 page_do_bit17_swizzling = obj_do_bit17_swizzling &&
                         (page_to_phys(page) & (1 << 17)) != 0;
 
@@ -732,8 +728,7 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
         int hit_slowpath = 0;
         int needs_clflush_after = 0;
         int needs_clflush_before = 0;
-        int i;
-        struct scatterlist *sg;
+        struct sg_page_iter sg_iter;
 
         user_data = to_user_ptr(args->data_ptr);
         remain = args->size;
@@ -768,13 +763,11 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
         offset = args->offset;
         obj->dirty = 1;
 
-        for_each_sg(obj->pages->sgl, sg, obj->pages->nents, i) {
-                struct page *page;
+        for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents,
+                         offset >> PAGE_SHIFT) {
+                struct page *page = sg_iter.page;
                 int partial_cacheline_write;
 
-                if (i < offset >> PAGE_SHIFT)
-                        continue;
-
                 if (remain <= 0)
                         break;
 
@@ -796,7 +789,6 @@ i915_gem_shmem_pwrite(struct drm_device *dev,
                         ((shmem_page_offset | page_length)
                                 & (boot_cpu_data.x86_clflush_size - 1));
 
-                page = sg_page(sg);
                 page_do_bit17_swizzling = obj_do_bit17_swizzling &&
                         (page_to_phys(page) & (1 << 17)) != 0;
 
diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
index 6a5af6828624..898615d2d5e2 100644
--- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
@@ -62,7 +62,7 @@ static struct sg_table *i915_gem_map_dma_buf(struct dma_buf_attachment *attachme
         src = obj->pages->sgl;
         dst = st->sgl;
         for (i = 0; i < obj->pages->nents; i++) {
-                sg_set_page(dst, sg_page(src), PAGE_SIZE, 0);
+                sg_set_page(dst, sg_page(src), src->length, 0);
                 dst = sg_next(dst);
                 src = sg_next(src);
         }
@@ -105,7 +105,7 @@ static void *i915_gem_dmabuf_vmap(struct dma_buf *dma_buf)
 {
         struct drm_i915_gem_object *obj = dma_buf->priv;
         struct drm_device *dev = obj->base.dev;
-        struct scatterlist *sg;
+        struct sg_page_iter sg_iter;
         struct page **pages;
         int ret, i;
 
@@ -124,14 +124,15 @@ static void *i915_gem_dmabuf_vmap(struct dma_buf *dma_buf)
 
         ret = -ENOMEM;
 
-        pages = drm_malloc_ab(obj->pages->nents, sizeof(struct page *));
+        pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
         if (pages == NULL)
                 goto error;
 
-        for_each_sg(obj->pages->sgl, sg, obj->pages->nents, i)
-                pages[i] = sg_page(sg);
+        i = 0;
+        for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0);
+                pages[i++] = sg_iter.page;
 
-        obj->dma_buf_vmapping = vmap(pages, obj->pages->nents, 0, PAGE_KERNEL);
+        obj->dma_buf_vmapping = vmap(pages, i, 0, PAGE_KERNEL);
         drm_free_large(pages);
 
         if (!obj->dma_buf_vmapping)
diff --git a/drivers/gpu/drm/i915/i915_gem_tiling.c b/drivers/gpu/drm/i915/i915_gem_tiling.c
index abcba2f5a788..f799708bcb85 100644
--- a/drivers/gpu/drm/i915/i915_gem_tiling.c
+++ b/drivers/gpu/drm/i915/i915_gem_tiling.c
@@ -473,28 +473,29 @@ i915_gem_swizzle_page(struct page *page)
 void
 i915_gem_object_do_bit_17_swizzle(struct drm_i915_gem_object *obj)
 {
-        struct scatterlist *sg;
-        int page_count = obj->base.size >> PAGE_SHIFT;
+        struct sg_page_iter sg_iter;
         int i;
 
         if (obj->bit_17 == NULL)
                 return;
 
-        for_each_sg(obj->pages->sgl, sg, page_count, i) {
-                struct page *page = sg_page(sg);
+        i = 0;
+        for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0) {
+                struct page *page = sg_iter.page;
                 char new_bit_17 = page_to_phys(page) >> 17;
                 if ((new_bit_17 & 0x1) !=
                     (test_bit(i, obj->bit_17) != 0)) {
                         i915_gem_swizzle_page(page);
                         set_page_dirty(page);
                 }
+                i++;
         }
 }
 
 void
 i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj)
 {
-        struct scatterlist *sg;
+        struct sg_page_iter sg_iter;
         int page_count = obj->base.size >> PAGE_SHIFT;
         int i;
 
@@ -508,11 +509,12 @@ i915_gem_object_save_bit_17_swizzle(struct drm_i915_gem_object *obj)
                 }
         }
 
-        for_each_sg(obj->pages->sgl, sg, page_count, i) {
-                struct page *page = sg_page(sg);
-                if (page_to_phys(page) & (1 << 17))
+        i = 0;
+        for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0) {
+                if (page_to_phys(sg_iter.page) & (1 << 17))
                         __set_bit(i, obj->bit_17);
                 else
                         __clear_bit(i, obj->bit_17);
+                i++;
         }
 }