drm/i915/bdw: Pin the ringbuffer backing object to GGTT on-demand

Same as with the context, pinning to GGTT regardless is harmful (it
badly fragments the GGTT and can even exhaust it).

Unfortunately, this case is also more complex than the previous one
because we need to map and access the ringbuffer in several places
along the execbuffer path (and we cannot make do by leaving the
default ringbuffer pinned, as before). Also, the context object
itself contains a pointer to the ringbuffer address that we have to
keep updated if we are going to allow the ringbuffer to move around.

v2: Same as with the context pinning, we cannot really do it during
an interrupt. Also, pin the default ringbuffers objects regardless
(makes error capture a lot easier).

v3: Rebased. Take a pin reference of the ringbuffer for each item
in the execlist request queue because the hardware may still be using
the ringbuffer after the MI_USER_INTERRUPT to notify the seqno update
is executed.  The ringbuffer must remain pinned until the context save
is complete.  No longer pin and unpin ringbuffer in
populate_lr_context() - this transient address is meaningless and the
pinning can cause a sleep while atomic.

v4: Moved ringbuffer pin and unpin into the lr_context_pin functions.
Downgraded pinning check BUG_ONs to WARN_ONs.

v5: Reinstated WARN_ONs for unexpected execlist states.  Removed unused
variable.

Issue: VIZ-4277
Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Signed-off-by: Thomas Daniel <thomas.daniel@intel.com>
Reviewed-by: Akash Goel <akash.goels@gmail.com>
Reviewed-by: Deepak S<deepak.s@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 50 insertions, 35 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index ae092589ea0c..0a4f35e735c3 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1722,13 +1722,42 @@ static int init_phys_status_page(struct intel_engine_cs *ring)
         return 0;
 }
 
-void intel_destroy_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
+void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
 {
-        if (!ringbuf->obj)
-                return;
-
         iounmap(ringbuf->virtual_start);
+        ringbuf->virtual_start = NULL;
         i915_gem_object_ggtt_unpin(ringbuf->obj);
+}
+
+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 drm_i915_gem_object *obj = ringbuf->obj;
+        int ret;
+
+        ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
+        if (ret)
+                return ret;
+
+        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;
+}
+
+void intel_destroy_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
+{
         drm_gem_object_unreference(&ringbuf->obj->base);
         ringbuf->obj = NULL;
 }
@@ -1736,12 +1765,7 @@ void intel_destroy_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
 int intel_alloc_ringbuffer_obj(struct drm_device *dev,
                                struct intel_ringbuffer *ringbuf)
 {
-        struct drm_i915_private *dev_priv = to_i915(dev);
         struct drm_i915_gem_object *obj;
-        int ret;
-
-        if (ringbuf->obj)
-                return 0;
 
         obj = NULL;
         if (!HAS_LLC(dev))
@@ -1754,30 +1778,9 @@ int intel_alloc_ringbuffer_obj(struct drm_device *dev,
         /* mark ring buffers as read-only from GPU side by default */
         obj->gt_ro = 1;
 
-        ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
-        if (ret)
-                goto err_unref;
-
-        ret = i915_gem_object_set_to_gtt_domain(obj, true);
-        if (ret)
-                goto err_unpin;
-
-        ringbuf->virtual_start =
-                ioremap_wc(dev_priv->gtt.mappable_base + i915_gem_obj_ggtt_offset(obj),
-                                ringbuf->size);
-        if (ringbuf->virtual_start == NULL) {
-                ret = -EINVAL;
-                goto err_unpin;
-        }
-
         ringbuf->obj = obj;
-        return 0;
 
-err_unpin:
-        i915_gem_object_ggtt_unpin(obj);
-err_unref:
-        drm_gem_object_unreference(&obj->base);
-        return ret;
+        return 0;
 }
 
 static int intel_init_ring_buffer(struct drm_device *dev,
@@ -1814,10 +1817,21 @@ static int intel_init_ring_buffer(struct drm_device *dev,
                         goto error;
         }
 
-        ret = intel_alloc_ringbuffer_obj(dev, ringbuf);
-        if (ret) {
-                DRM_ERROR("Failed to allocate ringbuffer %s: %d\n", ring->name, ret);
-                goto error;
+        if (ringbuf->obj == NULL) {
+                ret = intel_alloc_ringbuffer_obj(dev, ringbuf);
+                if (ret) {
+                        DRM_ERROR("Failed to allocate ringbuffer %s: %d\n",
+                                        ring->name, ret);
+                        goto error;
+                }
+
+                ret = intel_pin_and_map_ringbuffer_obj(dev, ringbuf);
+                if (ret) {
+                        DRM_ERROR("Failed to pin and map ringbuffer %s: %d\n",
+                                        ring->name, ret);
+                        intel_destroy_ringbuffer_obj(ringbuf);
+                        goto error;
+                }
         }
 
         /* Workaround an erratum on the i830 which causes a hang if
@@ -1858,6 +1872,7 @@ void intel_cleanup_ring_buffer(struct intel_engine_cs *ring)
         intel_stop_ring_buffer(ring);
         WARN_ON(!IS_GEN2(ring->dev) && (I915_READ_MODE(ring) & MODE_IDLE) == 0);
 
+        intel_unpin_ringbuffer_obj(ringbuf);
         intel_destroy_ringbuffer_obj(ringbuf);
         ring->preallocated_lazy_request = NULL;
         ring->outstanding_lazy_seqno = 0;