From: Tvrtko Ursulin <tvrtko.ursu...@intel.com>

With the addition of __sg_alloc_table_from_pages we can control
the maximum coallescing size and eliminate a separate path for
allocating backing store here.

Similar to 871dfbd67d4e ("drm/i915: Allow compaction upto
SWIOTLB max segment size") this enables more compact sg lists to
be created and so has a beneficial effect on workloads with many
and/or large objects of this class.

v2:
 * Rename helper to i915_sg_segment_size and fix swiotlb override.
 * Commit message update.

v3:
 * Actually include the swiotlb override fix.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
Cc: Chris Wilson <ch...@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.h         | 11 +++++++++++
 drivers/gpu/drm/i915/i915_gem.c         | 15 +--------------
 drivers/gpu/drm/i915/i915_gem_userptr.c | 28 ++++++----------------------
 3 files changed, 18 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 30777dee3f9c..38a555c9c44b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -4175,4 +4175,15 @@ int remap_io_mapping(struct vm_area_struct *vma,
        __T;                                                            \
 })
 
+static inline unsigned int i915_sg_segment_size(void)
+{
+#if IS_ENABLED(CONFIG_SWIOTLB)
+       unsigned int nr_tbl = swiotlb_nr_tbl();
+
+       return nr_tbl > 0 ? nr_tbl << IO_TLB_SHIFT : UINT_MAX;
+#else
+       return UINT_MAX;
+#endif
+}
+
 #endif
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1c20edba7f2a..cb4c188a395c 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2223,15 +2223,6 @@ void __i915_gem_object_put_pages(struct 
drm_i915_gem_object *obj,
        mutex_unlock(&obj->mm.lock);
 }
 
-static unsigned int swiotlb_max_size(void)
-{
-#if IS_ENABLED(CONFIG_SWIOTLB)
-       return rounddown(swiotlb_nr_tbl() << IO_TLB_SHIFT, PAGE_SIZE);
-#else
-       return 0;
-#endif
-}
-
 static void i915_sg_trim(struct sg_table *orig_st)
 {
        struct sg_table new_st;
@@ -2267,7 +2258,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object 
*obj)
        struct sgt_iter sgt_iter;
        struct page *page;
        unsigned long last_pfn = 0;     /* suppress gcc warning */
-       unsigned int max_segment;
+       unsigned int max_segment = rounddown(i915_sg_segment_size(), PAGE_SIZE);
        int ret;
        gfp_t gfp;
 
@@ -2278,10 +2269,6 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object 
*obj)
        GEM_BUG_ON(obj->base.read_domains & I915_GEM_GPU_DOMAINS);
        GEM_BUG_ON(obj->base.write_domain & I915_GEM_GPU_DOMAINS);
 
-       max_segment = swiotlb_max_size();
-       if (!max_segment)
-               max_segment = rounddown(UINT_MAX, PAGE_SIZE);
-
        st = kmalloc(sizeof(*st), GFP_KERNEL);
        if (st == NULL)
                return ERR_PTR(-ENOMEM);
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c 
b/drivers/gpu/drm/i915/i915_gem_userptr.c
index 64261639f547..b4461f1832a6 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -390,36 +390,20 @@ struct get_pages_work {
        struct task_struct *task;
 };
 
-#if IS_ENABLED(CONFIG_SWIOTLB)
-#define swiotlb_active() swiotlb_nr_tbl()
-#else
-#define swiotlb_active() 0
-#endif
-
 static int
 st_set_pages(struct sg_table **st, struct page **pvec, int num_pages)
 {
-       struct scatterlist *sg;
-       int ret, n;
+       int ret;
 
        *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;
-       }
+       ret = __sg_alloc_table_from_pages(*st, pvec, num_pages, 0,
+                                         num_pages << PAGE_SHIFT,
+                                         GFP_KERNEL, i915_sg_segment_size());
+       if (ret)
+               goto err;
 
        return 0;
 
-- 
2.7.4

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