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drm/i915: Stop setting wraparound seqno on initialisation 

We have testcases to ensure that seqno wraparound works fine, so we can
forgo forcing everyone to encounter seqno wraparound during early
uptime. seqno wraparound incurs a full GPU stall so not forcing it
will eliminate one jitter from the early system. Using the testcases, we
have very deterministic testing which given how difficult it would be to
debug an issue (GPU hang) stemming from a wraparound using pure
postmortem analysis I see no value in forcing a wrap during boot.

Advancing the global next_seqno after a GPU reset is equally pointless.

References? https://bugs.freedesktop.org/show_bug.cgi?id=95023
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1467390209-3576-15-git-send-email-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2016-07-01 17:23:24 +01:00
parent 3d5564e910
commit 1137fa8615
1 changed files with 0 additions and 14 deletions
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14
drivers/gpu/drm/i915/i915_gem.c
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@ -5119,12 +5119,6 @@ i915_gem_init_hw(struct drm_device *dev)
if (ret)
goto out;
/*
* Increment the next seqno by 0x100 so we have a visible break
* on re-initialisation
*/
ret = i915_gem_set_seqno(dev, dev_priv->next_seqno+0x100);
out:
intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
return ret;
@ -5267,14 +5261,6 @@ i915_gem_load_init(struct drm_device *dev)
dev_priv->relative_constants_mode = I915_EXEC_CONSTANTS_REL_GENERAL;
/*
* Set initial sequence number for requests.
* Using this number allows the wraparound to happen early,
* catching any obvious problems.
*/
dev_priv->next_seqno = ((u32)~0 - 0x1100);
dev_priv->last_seqno = ((u32)~0 - 0x1101);
INIT_LIST_HEAD(&dev_priv->mm.fence_list);
init_waitqueue_head(&dev_priv->pending_flip_queue);