[Intel-gfx] [PATCH 13/15] drm/i915: Stop setting wraparound seqno on initialisation

Daniel Vetter daniel at ffwll.ch
Fri Dec 4 01:36:45 PST 2015

On Tue, Dec 01, 2015 at 04:57:11PM +0000, Dave Gordon wrote:
> On 29/11/15 08:48, Chris Wilson wrote:
> >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.
> >
> >Advancing the global next_seqno after a GPU reset is equally pointless.
> >
> >Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> The real bug is that seqno wraparound forces GPU idle, can we fix that
> instead?

hw semaphores will fall over if we don't, but I guess we can forgo the
idle if there's no hw semaphores enabled. And yeah I'd like to keep this
little trick to exercise wrap-around more often too.
Daniel Vetter
Software Engineer, Intel Corporation

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