On 10/10/2016 23:27, Chris Wilson wrote:
commit 1625e7e549c5 ("drm/i915: make compact dma scatter lists creation
work with SWIOTLB backend") took a heavy handed approach to undo the
scatterlist compaction in the face of SWIOTLB. (The compaction hit a bug
whereby we tried to pass a segment larger than SWIOTLB could handle.) We
can be a little more intelligent and try compacting the scatterlist up
to the maximum SWIOTLB segment size (when using SWIOTLB).
v2: Tidy sg_mark_end() and cpp
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
CC: Imre Deak <imre.deak@xxxxxxxxx>
CC: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index dff8d05d80ee..50fd611926cb 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2201,6 +2201,15 @@ unlock:
mutex_unlock(&obj->mm.lock);
}
+static unsigned long swiotlb_max_size(void)
+{
+#if IS_ENABLED(CONFIG_SWIOTLB)
+ return swiotlb_nr_tbl() << IO_TLB_SHIFT;
+#else
+ return 0;
+#endif
+}
+
static struct sg_table *
i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
{
@@ -2212,6 +2221,7 @@ 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 long max_segment;
int ret;
gfp_t gfp;
@@ -2222,6 +2232,10 @@ 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 = obj->base.size;
+
st = kmalloc(sizeof(*st), GFP_KERNEL);
if (st == NULL)
return ERR_PTR(-ENOMEM);
@@ -2263,15 +2277,9 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
goto err_pages;
}
}
-#ifdef CONFIG_SWIOTLB
- if (swiotlb_nr_tbl()) {
- st->nents++;
- sg_set_page(sg, page, PAGE_SIZE, 0);
- sg = sg_next(sg);
- continue;
- }
-#endif
- if (!i || page_to_pfn(page) != last_pfn + 1) {
+ if (!i ||
+ sg->length >= max_segment ||
+ page_to_pfn(page) != last_pfn + 1) {
if (i)
sg = sg_next(sg);
st->nents++;
@@ -2284,9 +2292,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
/* Check that the i965g/gm workaround works. */
WARN_ON((gfp & __GFP_DMA32) && (last_pfn >= 0x00100000UL));
}
-#ifdef CONFIG_SWIOTLB
- if (!swiotlb_nr_tbl())
-#endif
+ if (sg) /* loop terminated early; short sg table */
sg_mark_end(sg);
ret = i915_gem_gtt_prepare_pages(obj, st);
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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