drm/i915: Preallocate next seqno before touching the ring
Based on the work by Mika Kuoppala, we realised that we need to handle
seqno wraparound prior to committing our changes to the ring. The most
obvious point then is to grab the seqno inside intel_ring_begin(), and
then to reuse that seqno for all ring operations until the next request.
As intel_ring_begin() can fail, the callers must already be prepared to
handle such failure and so we can safely add further checks.
This patch looks like it should be split up into the interface
changes and the tweaks to move seqno wrapping from the execbuffer into
the core seqno increment. However, I found no easy way to break it into
incremental steps without introducing further broken behaviour.
v2: Mika found a silly mistake and a subtle error in the existing code;
inside i915_gem_retire_requests() we were resetting the sync_seqno of
the target ring based on the seqno from this ring - which are only
related by the order of their allocation, not retirement. Hence we were
applying the optimisation that the rings were synchronised too early,
fortunately the only real casualty there is the handling of seqno
wrapping.
v3: Do not forget to reset the sync_seqno upon module reinitialisation,
ala resume.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=863861
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com> [v2]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 47c62f5..45491c1a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1417,8 +1417,7 @@
int i915_gem_object_sync(struct drm_i915_gem_object *obj,
struct intel_ring_buffer *to);
void i915_gem_object_move_to_active(struct drm_i915_gem_object *obj,
- struct intel_ring_buffer *ring,
- u32 seqno);
+ struct intel_ring_buffer *ring);
int i915_gem_dumb_create(struct drm_file *file_priv,
struct drm_device *dev,
@@ -1436,7 +1435,7 @@
return (int32_t)(seq1 - seq2) >= 0;
}
-u32 i915_gem_next_request_seqno(struct intel_ring_buffer *ring);
+extern int i915_gem_get_seqno(struct drm_device *dev, u32 *seqno);
int __must_check i915_gem_object_get_fence(struct drm_i915_gem_object *obj);
int __must_check i915_gem_object_put_fence(struct drm_i915_gem_object *obj);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9be450e..3b9b250 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1857,11 +1857,11 @@
void
i915_gem_object_move_to_active(struct drm_i915_gem_object *obj,
- struct intel_ring_buffer *ring,
- u32 seqno)
+ struct intel_ring_buffer *ring)
{
struct drm_device *dev = obj->base.dev;
struct drm_i915_private *dev_priv = dev->dev_private;
+ u32 seqno = intel_ring_get_seqno(ring);
BUG_ON(ring == NULL);
obj->ring = ring;
@@ -1922,26 +1922,54 @@
WARN_ON(i915_verify_lists(dev));
}
-static u32
-i915_gem_get_seqno(struct drm_device *dev)
+static int
+i915_gem_handle_seqno_wrap(struct drm_device *dev)
{
- drm_i915_private_t *dev_priv = dev->dev_private;
- u32 seqno = dev_priv->next_seqno;
+ struct drm_i915_private *dev_priv = dev->dev_private;
+ struct intel_ring_buffer *ring;
+ int ret, i, j;
- /* reserve 0 for non-seqno */
- if (++dev_priv->next_seqno == 0)
- dev_priv->next_seqno = 1;
+ /* The hardware uses various monotonic 32-bit counters, if we
+ * detect that they will wraparound we need to idle the GPU
+ * and reset those counters.
+ */
+ ret = 0;
+ for_each_ring(ring, dev_priv, i) {
+ for (j = 0; j < ARRAY_SIZE(ring->sync_seqno); j++)
+ ret |= ring->sync_seqno[j] != 0;
+ }
+ if (ret == 0)
+ return ret;
- return seqno;
+ ret = i915_gpu_idle(dev);
+ if (ret)
+ return ret;
+
+ i915_gem_retire_requests(dev);
+ for_each_ring(ring, dev_priv, i) {
+ for (j = 0; j < ARRAY_SIZE(ring->sync_seqno); j++)
+ ring->sync_seqno[j] = 0;
+ }
+
+ return 0;
}
-u32
-i915_gem_next_request_seqno(struct intel_ring_buffer *ring)
+int
+i915_gem_get_seqno(struct drm_device *dev, u32 *seqno)
{
- if (ring->outstanding_lazy_request == 0)
- ring->outstanding_lazy_request = i915_gem_get_seqno(ring->dev);
+ struct drm_i915_private *dev_priv = dev->dev_private;
- return ring->outstanding_lazy_request;
+ /* reserve 0 for non-seqno */
+ if (dev_priv->next_seqno == 0) {
+ int ret = i915_gem_handle_seqno_wrap(dev);
+ if (ret)
+ return ret;
+
+ dev_priv->next_seqno = 1;
+ }
+
+ *seqno = dev_priv->next_seqno++;
+ return 0;
}
int
@@ -1952,7 +1980,6 @@
drm_i915_private_t *dev_priv = ring->dev->dev_private;
struct drm_i915_gem_request *request;
u32 request_ring_position;
- u32 seqno;
int was_empty;
int ret;
@@ -1971,7 +1998,6 @@
if (request == NULL)
return -ENOMEM;
- seqno = i915_gem_next_request_seqno(ring);
/* Record the position of the start of the request so that
* should we detect the updated seqno part-way through the
@@ -1980,15 +2006,13 @@
*/
request_ring_position = intel_ring_get_tail(ring);
- ret = ring->add_request(ring, &seqno);
+ ret = ring->add_request(ring);
if (ret) {
kfree(request);
return ret;
}
- trace_i915_gem_request_add(ring, seqno);
-
- request->seqno = seqno;
+ request->seqno = intel_ring_get_seqno(ring);
request->ring = ring;
request->tail = request_ring_position;
request->emitted_jiffies = jiffies;
@@ -2006,6 +2030,7 @@
spin_unlock(&file_priv->mm.lock);
}
+ trace_i915_gem_request_add(ring, request->seqno);
ring->outstanding_lazy_request = 0;
if (!dev_priv->mm.suspended) {
@@ -2022,7 +2047,7 @@
}
if (out_seqno)
- *out_seqno = seqno;
+ *out_seqno = request->seqno;
return 0;
}
@@ -2120,7 +2145,6 @@
i915_gem_retire_requests_ring(struct intel_ring_buffer *ring)
{
uint32_t seqno;
- int i;
if (list_empty(&ring->request_list))
return;
@@ -2129,10 +2153,6 @@
seqno = ring->get_seqno(ring, true);
- for (i = 0; i < ARRAY_SIZE(ring->sync_seqno); i++)
- if (seqno >= ring->sync_seqno[i])
- ring->sync_seqno[i] = 0;
-
while (!list_empty(&ring->request_list)) {
struct drm_i915_gem_request *request;
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 0e510df..a3f06bc 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -410,9 +410,8 @@
* MI_SET_CONTEXT instead of when the next seqno has completed.
*/
if (from_obj != NULL) {
- u32 seqno = i915_gem_next_request_seqno(ring);
from_obj->base.read_domains = I915_GEM_DOMAIN_INSTRUCTION;
- i915_gem_object_move_to_active(from_obj, ring, seqno);
+ i915_gem_object_move_to_active(from_obj, ring);
/* As long as MI_SET_CONTEXT is serializing, ie. it flushes the
* whole damn pipeline, we don't need to explicitly mark the
* object dirty. The only exception is that the context must be
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 48e4317..ee8f97f 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -713,8 +713,7 @@
static void
i915_gem_execbuffer_move_to_active(struct list_head *objects,
- struct intel_ring_buffer *ring,
- u32 seqno)
+ struct intel_ring_buffer *ring)
{
struct drm_i915_gem_object *obj;
@@ -726,10 +725,10 @@
obj->base.write_domain = obj->base.pending_write_domain;
obj->fenced_gpu_access = obj->pending_fenced_gpu_access;
- i915_gem_object_move_to_active(obj, ring, seqno);
+ i915_gem_object_move_to_active(obj, ring);
if (obj->base.write_domain) {
obj->dirty = 1;
- obj->last_write_seqno = seqno;
+ obj->last_write_seqno = intel_ring_get_seqno(ring);
if (obj->pin_count) /* check for potential scanout */
intel_mark_fb_busy(obj);
}
@@ -789,7 +788,6 @@
struct intel_ring_buffer *ring;
u32 ctx_id = i915_execbuffer2_get_context_id(*args);
u32 exec_start, exec_len;
- u32 seqno;
u32 mask;
u32 flags;
int ret, mode, i;
@@ -994,22 +992,6 @@
if (ret)
goto err;
- seqno = i915_gem_next_request_seqno(ring);
- for (i = 0; i < ARRAY_SIZE(ring->sync_seqno); i++) {
- if (seqno < ring->sync_seqno[i]) {
- /* The GPU can not handle its semaphore value wrapping,
- * so every billion or so execbuffers, we need to stall
- * the GPU in order to reset the counters.
- */
- ret = i915_gpu_idle(dev);
- if (ret)
- goto err;
- i915_gem_retire_requests(dev);
-
- BUG_ON(ring->sync_seqno[i]);
- }
- }
-
ret = i915_switch_context(ring, file, ctx_id);
if (ret)
goto err;
@@ -1035,8 +1017,6 @@
goto err;
}
- trace_i915_gem_ring_dispatch(ring, seqno, flags);
-
exec_start = batch_obj->gtt_offset + args->batch_start_offset;
exec_len = args->batch_len;
if (cliprects) {
@@ -1060,7 +1040,9 @@
goto err;
}
- i915_gem_execbuffer_move_to_active(&objects, ring, seqno);
+ trace_i915_gem_ring_dispatch(ring, intel_ring_get_seqno(ring), flags);
+
+ i915_gem_execbuffer_move_to_active(&objects, ring);
i915_gem_execbuffer_retire_commands(dev, file, ring);
err:
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 987eb5f..e4682cd 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -555,12 +555,11 @@
static void
update_mboxes(struct intel_ring_buffer *ring,
- u32 seqno,
- u32 mmio_offset)
+ u32 mmio_offset)
{
intel_ring_emit(ring, MI_LOAD_REGISTER_IMM(1));
intel_ring_emit(ring, mmio_offset);
- intel_ring_emit(ring, seqno);
+ intel_ring_emit(ring, ring->outstanding_lazy_request);
}
/**
@@ -573,8 +572,7 @@
* This acts like a signal in the canonical semaphore.
*/
static int
-gen6_add_request(struct intel_ring_buffer *ring,
- u32 *seqno)
+gen6_add_request(struct intel_ring_buffer *ring)
{
u32 mbox1_reg;
u32 mbox2_reg;
@@ -587,13 +585,11 @@
mbox1_reg = ring->signal_mbox[0];
mbox2_reg = ring->signal_mbox[1];
- *seqno = i915_gem_next_request_seqno(ring);
-
- update_mboxes(ring, *seqno, mbox1_reg);
- update_mboxes(ring, *seqno, mbox2_reg);
+ update_mboxes(ring, mbox1_reg);
+ update_mboxes(ring, mbox2_reg);
intel_ring_emit(ring, MI_STORE_DWORD_INDEX);
intel_ring_emit(ring, I915_GEM_HWS_INDEX << MI_STORE_DWORD_INDEX_SHIFT);
- intel_ring_emit(ring, *seqno);
+ intel_ring_emit(ring, ring->outstanding_lazy_request);
intel_ring_emit(ring, MI_USER_INTERRUPT);
intel_ring_advance(ring);
@@ -650,10 +646,8 @@
} while (0)
static int
-pc_render_add_request(struct intel_ring_buffer *ring,
- u32 *result)
+pc_render_add_request(struct intel_ring_buffer *ring)
{
- u32 seqno = i915_gem_next_request_seqno(ring);
struct pipe_control *pc = ring->private;
u32 scratch_addr = pc->gtt_offset + 128;
int ret;
@@ -674,7 +668,7 @@
PIPE_CONTROL_WRITE_FLUSH |
PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE);
intel_ring_emit(ring, pc->gtt_offset | PIPE_CONTROL_GLOBAL_GTT);
- intel_ring_emit(ring, seqno);
+ intel_ring_emit(ring, ring->outstanding_lazy_request);
intel_ring_emit(ring, 0);
PIPE_CONTROL_FLUSH(ring, scratch_addr);
scratch_addr += 128; /* write to separate cachelines */
@@ -693,11 +687,10 @@
PIPE_CONTROL_TEXTURE_CACHE_INVALIDATE |
PIPE_CONTROL_NOTIFY);
intel_ring_emit(ring, pc->gtt_offset | PIPE_CONTROL_GLOBAL_GTT);
- intel_ring_emit(ring, seqno);
+ intel_ring_emit(ring, ring->outstanding_lazy_request);
intel_ring_emit(ring, 0);
intel_ring_advance(ring);
- *result = seqno;
return 0;
}
@@ -885,25 +878,20 @@
}
static int
-i9xx_add_request(struct intel_ring_buffer *ring,
- u32 *result)
+i9xx_add_request(struct intel_ring_buffer *ring)
{
- u32 seqno;
int ret;
ret = intel_ring_begin(ring, 4);
if (ret)
return ret;
- seqno = i915_gem_next_request_seqno(ring);
-
intel_ring_emit(ring, MI_STORE_DWORD_INDEX);
intel_ring_emit(ring, I915_GEM_HWS_INDEX << MI_STORE_DWORD_INDEX_SHIFT);
- intel_ring_emit(ring, seqno);
+ intel_ring_emit(ring, ring->outstanding_lazy_request);
intel_ring_emit(ring, MI_USER_INTERRUPT);
intel_ring_advance(ring);
- *result = seqno;
return 0;
}
@@ -1110,6 +1098,7 @@
INIT_LIST_HEAD(&ring->active_list);
INIT_LIST_HEAD(&ring->request_list);
ring->size = 32 * PAGE_SIZE;
+ memset(ring->sync_seqno, 0, sizeof(ring->sync_seqno));
init_waitqueue_head(&ring->irq_queue);
@@ -1338,6 +1327,15 @@
return -EBUSY;
}
+static int
+intel_ring_alloc_seqno(struct intel_ring_buffer *ring)
+{
+ if (ring->outstanding_lazy_request)
+ return 0;
+
+ return i915_gem_get_seqno(ring->dev, &ring->outstanding_lazy_request);
+}
+
int intel_ring_begin(struct intel_ring_buffer *ring,
int num_dwords)
{
@@ -1349,6 +1347,11 @@
if (ret)
return ret;
+ /* Preallocate the olr before touching the ring */
+ ret = intel_ring_alloc_seqno(ring);
+ if (ret)
+ return ret;
+
if (unlikely(ring->tail + n > ring->effective_size)) {
ret = intel_wrap_ring_buffer(ring);
if (unlikely(ret))
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 5af65b8..0e61302 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -70,8 +70,7 @@
int __must_check (*flush)(struct intel_ring_buffer *ring,
u32 invalidate_domains,
u32 flush_domains);
- int (*add_request)(struct intel_ring_buffer *ring,
- u32 *seqno);
+ int (*add_request)(struct intel_ring_buffer *ring);
/* Some chipsets are not quite as coherent as advertised and need
* an expensive kick to force a true read of the up-to-date seqno.
* However, the up-to-date seqno is not always required and the last
@@ -205,7 +204,6 @@
void intel_ring_advance(struct intel_ring_buffer *ring);
-u32 intel_ring_get_seqno(struct intel_ring_buffer *ring);
int intel_ring_flush_all_caches(struct intel_ring_buffer *ring);
int intel_ring_invalidate_all_caches(struct intel_ring_buffer *ring);
@@ -221,6 +219,12 @@
return ring->tail;
}
+static inline u32 intel_ring_get_seqno(struct intel_ring_buffer *ring)
+{
+ BUG_ON(ring->outstanding_lazy_request == 0);
+ return ring->outstanding_lazy_request;
+}
+
static inline void i915_trace_irq_get(struct intel_ring_buffer *ring, u32 seqno)
{
if (ring->trace_irq_seqno == 0 && ring->irq_get(ring))