[PATCH 1/3] drm/i915: Map the ringbuffer using WB on LLC machines

Chris Wilson
2015-10-08T12:40:04Z

If we have llc coherency, we can write directly into the ringbuffer
using ordinary cached writes rather than forcing WC access.

v2: An important consequence is that we can forgo the mappable request
for WB ringbuffers, allowing for many more simultaneous contexts.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
drivers/gpu/drm/i915/intel_ringbuffer.c | 70 ++++++++++++++++++++++++++-------
1 file changed, 56 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index d608be46ea6e..f81ec7785fac 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1966,11 +1966,35 @@ static int init_phys_status_page(struct intel_engine_cs *ring)

void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
{
- iounmap(ringbuf->virtual_start);
+ if (HAS_LLC(ringbuf->obj->base.dev) && !ringbuf->obj->stolen)
+ vunmap(ringbuf->virtual_start);
+ else
+ iounmap(ringbuf->virtual_start);
ringbuf->virtual_start = NULL;
i915_gem_object_ggtt_unpin(ringbuf->obj);
}

+static u32 *vmap_obj(struct drm_i915_gem_object *obj)
+{
+ struct sg_page_iter sg_iter;
+ struct page **pages;
+ void *addr;
+ int i;
+
+ pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
+ if (pages == NULL)
+ return NULL;
+
+ i = 0;
+ for_each_sg_page(obj->pages->sgl, &sg_iter, obj->pages->nents, 0)
+ pages[i++] = sg_page_iter_page(&sg_iter);
+
+ addr = vmap(pages, i, 0, PAGE_KERNEL);
+ drm_free_large(pages);
+
+ return addr;
+}
+
int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
struct intel_ringbuffer *ringbuf)
{
@@ -1978,21 +2002,39 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
struct drm_i915_gem_object *obj = ringbuf->obj;
int ret;

- ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
- if (ret)
- return ret;
+ if (HAS_LLC(dev_priv) && !obj->stolen) {
+ ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, 0);
+ if (ret)
+ return ret;

- ret = i915_gem_object_set_to_gtt_domain(obj, true);
- if (ret) {
- i915_gem_object_ggtt_unpin(obj);
- return ret;
- }
+ ret = i915_gem_object_set_to_cpu_domain(obj, true);
+ if (ret) {
+ i915_gem_object_ggtt_unpin(obj);
+ return ret;
+ }
+
+ ringbuf->virtual_start = vmap_obj(obj);
+ if (ringbuf->virtual_start == NULL) {
+ i915_gem_object_ggtt_unpin(obj);
+ return -ENOMEM;
+ }
+ } else {
+ ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
+ if (ret)
+ return ret;

- ringbuf->virtual_start = ioremap_wc(dev_priv->gtt.mappable_base +
- i915_gem_obj_ggtt_offset(obj), ringbuf->size);
- if (ringbuf->virtual_start == NULL) {
- i915_gem_object_ggtt_unpin(obj);
- return -EINVAL;
+ ret = i915_gem_object_set_to_gtt_domain(obj, true);
+ if (ret) {
+ i915_gem_object_ggtt_unpin(obj);
+ return ret;
+ }
+
+ ringbuf->virtual_start = ioremap_wc(dev_priv->gtt.mappable_base +
+ i915_gem_obj_ggtt_offset(obj), ringbuf->size);
+ if (ringbuf->virtual_start == NULL) {
+ i915_gem_object_ggtt_unpin(obj);
+ return -EINVAL;
+ }
}

return 0;
--
2.6.1