[Intel-gfx] [PATCH] drm/i915/icl: Adjust BSD2 semantics to mean any second VCS instance

[Bloomfield, Jon]

> -----Original Message-----
> From: Tvrtko Ursulin <tursulin at ursulin.net>
> Sent: Wednesday, April 18, 2018 2:34 AM
> To: Intel-gfx at lists.freedesktop.org
> Cc: tursulin at ursulin.net; Ursulin, Tvrtko <tvrtko.ursulin at intel.com>; Chris
> Wilson <chris at chris-wilson.co.uk>; Bloomfield, Jon
> <jon.bloomfield at intel.com>; Ye, Tony <tony.ye at intel.com>
> Subject: [PATCH] drm/i915/icl: Adjust BSD2 semantics to mean any second
> VCS instance
> 
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> Currently our driver assumes BSD2 means hardware engine instance number
> two. This does not work for Icelake parts with two VCS engines, but which
> are hardware instances 0 and 2, and not 0 and 1 as with previous parts.
> 
> This makes the second engine not discoverable via HAS_BSD2 get param, nor
> it can be targetted by execbuf.
> 
> While we are working on the next generation execbuf put in a hack which
> allows discovery and access to this second VCS engine using legacy ABI.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Jon Bloomfield <jon.bloomfield at intel.com>
> Cc: Tony Ye <tony.ye at intel.com>
I would advocate this patch being merged while the new execbuf API is being
developed. Currently there is no way to submit to 2 engine skus with non-sequential
engine id's. This doesn't introduce a new ABI, and there is no reason that I can see
that the new execbuf solution couldn't be made backward compatible with this.

Reviewed-by: Jon Bloomfield <jon.bloomfield at intel.com>