[Intel-gfx] [PATCH v2 1/7] drm/i915/perf: rework aging tail workaround

[Chris Wilson]

Quoting Lionel Landwerlin (2019-02-18 18:35:28)
> We're about to introduce an options to open the perf stream, giving
> the user ability to configure how often it wants the kernel to poll
> the OA registers for available data.
> 
> Right now the workaround against the OA tail pointer race condition
> requires at least twice the internal kernel polling timer to make any
> data available.

I think this code is bogus. I do not think there is an aging problem on
hsw+, the only cause of zeroes being written that I've found is from
changing configs.
-Chris