On 11/12/15 01:17, yu.dai@xxxxxxxxx wrote:
From: Alex Dai <yu.dai@xxxxxxxxx>
Split GuC work queue space checking from submission and move it to
ring_alloc_request_extras. The reason is that failure in later
i915_add_request() won't be handled. In the case timeout happens,
driver can return early in order to handle the error.
v1: Move wq_reserve_space to ring_reserve_space
v2: Move wq_reserve_space to alloc_request_extras (Chris Wilson)
v3: The work queue head pointer is cached by driver now. So we can
quickly return if space is available.
s/reserve/check/g (Dave Gordon)
Signed-off-by: Alex Dai <yu.dai@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_guc_submission.c | 34 ++++++++++++++++++------------
drivers/gpu/drm/i915/intel_guc.h | 2 ++
drivers/gpu/drm/i915/intel_lrc.c | 6 ++++++
3 files changed, 28 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
index 226e9c0..cb8e1f71 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -207,6 +207,9 @@ static int guc_ring_doorbell(struct i915_guc_client *gc)
/* Update the tail so it is visible to GuC */
desc->tail = gc->wq_tail;
+ /* Cache the head where GuC is processing */
+ gc->wq_head = desc->head;
+
This could be at the end of this function, thus:
/* update the cookie to newly read cookie from GuC */
db_cmp.cookie = db_ret.cookie;
db_exc.cookie = db_ret.cookie + 1;
if (db_exc.cookie == 0)
db_exc.cookie = 1;
}
+ /* Finally, update the cached copy of the GuC's WQ head */
+ gc->wq_head = desc->head;
+
kunmap_atomic(base);
return ret;
}
which might increase the chance that we will get an updated value and
thus avoid having to spinwait on the next check().
/* current cookie */
db_cmp.db_status = GUC_DOORBELL_ENABLED;
db_cmp.cookie = gc->cookie;
@@ -472,28 +475,30 @@ static void guc_fini_ctx_desc(struct intel_guc *guc,
sizeof(desc) * client->ctx_index);
}
-/* Get valid workqueue item and return it back to offset */
-static int guc_get_workqueue_space(struct i915_guc_client *gc, u32 *offset)
+int i915_guc_wq_check_space(struct i915_guc_client *gc)
{
struct guc_process_desc *desc;
void *base;
u32 size = sizeof(struct guc_wq_item);
int ret = -ETIMEDOUT, timeout_counter = 200;
+ if (!gc)
+ return 0;
+
+ /* Quickly return if wq space is available since last time we cache the
+ * head position. */
+ if (CIRC_SPACE(gc->wq_tail, gc->wq_head, gc->wq_size) >= size)
+ return 0;
+
base = kmap_atomic(i915_gem_object_get_page(gc->client_obj, 0));
desc = base + gc->proc_desc_offset;
while (timeout_counter-- > 0) {
- if (CIRC_SPACE(gc->wq_tail, desc->head, gc->wq_size) >= size) {
- *offset = gc->wq_tail;
+ gc->wq_head = desc->head;
- /* advance the tail for next workqueue item */
- gc->wq_tail += size;
- gc->wq_tail &= gc->wq_size - 1;
-
- /* this will break the loop */
- timeout_counter = 0;
+ if (CIRC_SPACE(gc->wq_tail, gc->wq_head, gc->wq_size) >= size) {
ret = 0;
+ break;
}
if (timeout_counter)
@@ -512,11 +517,8 @@ static int guc_add_workqueue_item(struct i915_guc_client *gc,
struct guc_wq_item *wqi;
void *base;
u32 tail, wq_len, wq_off = 0;
- int ret;
- ret = guc_get_workqueue_space(gc, &wq_off);
- if (ret)
- return ret;
+ wq_off = gc->wq_tail;
Conversely, I'd prefer the updates below to be here instead; also the
check that I mentioned last time:
+ u32 space = CIRC_SPACE(gc->wq_tail, gc->wq_head, gc->wq_size);
+ if (WARN_ON(space < sizeof(struct guc_wq_item))
+ return -ENOSPC; /* shouldn't happen */
+
+ /* postincrement WQ tail for next time */
+ wq_off = gc->wq_tail;
+ gc->wq_tail += sizeof(struct guc_wq_item);
+ gc->wq_tail &= gc->wq_size - 1;
/* For now workqueue item is 4 DWs; workqueue buffer is 2 pages. So we
* should not have the case where structure wqi is across page, neither
@@ -551,6 +553,10 @@ static int guc_add_workqueue_item(struct i915_guc_client *gc,
kunmap_atomic(base);
+ /* advance the tail for next workqueue item */
+ gc->wq_tail += sizeof(struct guc_wq_item);
+ gc->wq_tail &= gc->wq_size - 1;
(moved to above)
+
return 0;
}
diff --git a/drivers/gpu/drm/i915/intel_guc.h b/drivers/gpu/drm/i915/intel_guc.h
index 0e048bf..5cf555d 100644
--- a/drivers/gpu/drm/i915/intel_guc.h
+++ b/drivers/gpu/drm/i915/intel_guc.h
@@ -43,6 +43,7 @@ struct i915_guc_client {
uint32_t wq_offset;
uint32_t wq_size;
uint32_t wq_tail;
+ uint32_t wq_head;
/* GuC submission statistics & status */
uint64_t submissions[I915_NUM_RINGS];
@@ -123,5 +124,6 @@ int i915_guc_submit(struct i915_guc_client *client,
struct drm_i915_gem_request *rq);
void i915_guc_submission_disable(struct drm_device *dev);
void i915_guc_submission_fini(struct drm_device *dev);
+int i915_guc_wq_check_space(struct i915_guc_client *client);
#endif
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index f96fb51..9605ce9 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -667,6 +667,12 @@ int intel_logical_ring_alloc_request_extras(struct drm_i915_gem_request *request
return ret;
}
+ /* Reserve GuC WQ space here (one request needs one WQ item) because
+ * the later i915_add_request() call can't fail. */
+ ret = i915_guc_wq_check_space(request->i915->guc.execbuf_client);
+ if (ret)
+ return ret;
+
return 0;
}
It looks odd to call a GuC-only function regardless of whether we're
using the GuC, so:
+ if (i915.enable_guc_submission) {
+ /*
+ * Check that the GuC has space for the request before
+ * going any further, as the i915_add_request() call
+ * later on mustn't fail ...
+ */
+ struct intel_guc *guc = &request->i915->guc;
+
+ ret = i915_guc_wq_check_space(guc->execbuf_client);
+ if (ret)
+ return ret;
+ }
.Dave.
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