Re: [Intel-gfx] [RFC 2/2] drm/i915: Use i915_vma_iomap from the ringbuffer

[Chris Wilson]

On Tue, Apr 12, 2016 at 04:56:52PM +0100, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin 
> 
> Similarly to i915_gem_object_pin_map on LLC platforms, we can
> use the new VMA based io mapping on !LLC to decrease the cost
> of ringbuf pinning and unpinning.

If you are going to mention pin_map, you open up the discussion that we
can avoid the mappable apertures requirement on !llc if we use pin_map
with a pgprot_writecombine. That's my preferred solution, caching the
ioremap is just a stopgap, or fallback for when we can't use direct CPU
access.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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[Intel-gfx] [RFC 2/2] drm/i915: Use i915_vma_iomap from the ringbuffer

[Tvrtko Ursulin]

From: Tvrtko Ursulin 

Similarly to i915_gem_object_pin_map on LLC platforms, we can
use the new VMA based io mapping on !LLC to decrease the cost
of ringbuf pinning and unpinning.

Signed-off-by: Tvrtko Ursulin 
---
 drivers/gpu/drm/i915/i915_gem_gtt.h |  2 ++
 drivers/gpu/drm/i915/intel_ringbuffer.c | 20 
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h 
b/drivers/gpu/drm/i915/i915_gem_gtt.h
index 526fdbc71ace..5dd0ddba5488 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -560,6 +560,8 @@ size_t
 i915_ggtt_view_size(struct drm_i915_gem_object *obj,
const struct i915_ggtt_view *view);
 
+struct drm_i915_private;
+
 /**
  * i915_vma_iomap - calls ioremap_wc to map the GGTT VMA via the aperture
  * @dev_priv: i915 private pointer
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c 
b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 41b604e69db7..8ac3342b4bdd 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2084,8 +2084,6 @@ void intel_unpin_ringbuffer_obj(struct intel_ringbuffer 
*ringbuf)
 {
if (HAS_LLC(ringbuf->obj->base.dev) && !ringbuf->obj->stolen)
i915_gem_object_unpin_map(ringbuf->obj);
-   else
-   iounmap(ringbuf->virtual_start);
ringbuf->vma = NULL;
i915_gem_object_ggtt_unpin(ringbuf->obj);
 }
@@ -2094,8 +2092,9 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device 
*dev,
 struct intel_ringbuffer *ringbuf)
 {
struct drm_i915_private *dev_priv = to_i915(dev);
-   struct i915_ggtt *ggtt = _priv->ggtt;
struct drm_i915_gem_object *obj = ringbuf->obj;
+   struct i915_vma *vma;
+   void *addr;
int ret;
 
if (HAS_LLC(dev_priv) && !obj->stolen) {
@@ -2112,6 +2111,8 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device 
*dev,
ret = -ENOMEM;
goto err_unpin;
}
+
+   vma = i915_gem_obj_to_ggtt(obj);
} else {
ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
if (ret)
@@ -2124,15 +2125,18 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device 
*dev,
/* Access through the GTT requires the device to be awake. */
assert_rpm_wakelock_held(dev_priv);
 
-   ringbuf->virtual_start = ioremap_wc(ggtt->mappable_base +
-   
i915_gem_obj_ggtt_offset(obj), ringbuf->size);
-   if (ringbuf->virtual_start == NULL) {
-   ret = -ENOMEM;
+   vma = i915_gem_obj_to_ggtt(obj);
+
+   addr = i915_vma_iomap(dev_priv, vma);
+   if (IS_ERR(addr)) {
+   ret = PTR_ERR(ringbuf->virtual_start);
goto err_unpin;
}
+
+   ringbuf->virtual_start = addr;
}
 
-   ringbuf->vma = i915_gem_obj_to_ggtt(obj);
+   ringbuf->vma = vma;
return 0;
 
 err_unpin:
-- 
1.9.1

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