[Intel-gfx] [PATCH 2/2] drm/i915: Add WaKBLVECSSemaphoreWaitPoll

[Joonas Lahtinen]

Quoting Mika Kuoppala (2018-06-05 19:03:57)
> There is a problem with kbl up to rev E0 where a heavy
> memory/fabric traffic from adjacent engine(s) can cause an engine
> reset to fail. This traffic can be from normal memory accesses
> or it can be from heavy polling on a semaphore wait.
> 
> For engine hogging causing a fail, we already fallback to
> full reset. Which effectively stops all engines and thus
> we only add a workaround documentation.
> 
> For the semaphore wait loop poll case, we add one microsecond
> poll interval to semaphore wait to guarantee bandwidth for
> the reset preration. The side effect is that we make semaphore
> completion latencies also 1us longer.
> 
> v2: Let full reset handle the adjacent engine idling (Chris)
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=106684
> References: VTHSD#2227190, HSDES#1604216706, BSID#0917
> Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>

Skip the RCS engine and this is;

Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Regards, Joonas