On 04/03/2020 16:02, Rafael Antognolli wrote:
On Wed, Mar 04, 2020 at 03:31:44PM +0000, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Enable FtrPerCtxtPreemptionGranularityControl bit and select thread-
group as the default preemption level.
v2:
* Remove register whitelisting (Rafael, Tony).
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Michał Winiarski <michal.winiarski@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: piotr.zdunowski@xxxxxxxxx
Cc: michal.mrozek@xxxxxxxxx
Cc: Tony Ye <tony.ye@xxxxxxxxx>
Cc: Rafael Antognolli <rafael.antognolli@xxxxxxxxx>
Thanks for CC'ing me. I also saw a reply from Jason yesterday, but I
don't see it in the list now (though my mail client a mess lately).
I saw nothing from Jason, but there was an email from you asking about
interface descriptors and whitelisting which is why I copied you.
But he asked whether it's possible for Media and OpenCL drivers to
also disable mid-thread preemption through the
INTERFACE_DESCRIPTOR_DATA, instead of from the kernel side, so we could
try to experiment with it in the future.
Also, do you have an idea of how broken it is? Or is it just not tested
because no driver is currently implementing it? And do you know if the
windows 3D drivers implement it at all? I see code in the driver that
seems to me that it's only disabled in certain cases...
To summarize, I think we should either:
1) Disable mid-thread preemption from the kernel and not whitelist
the register (just like you do in this patch); or
2) Not do anything at all from the kernel, and let userspace disable
it if needed.
I think 2) is better, if it's not an issue to the other userspace
drivers (OpenCL and Media).
I know it is somewhat broken like in
https://gitlab.freedesktop.org/drm/intel/issues/1293.
And I know OpenCL and Media would prefer i915 to handle it, but that's
always the case. :) OpenCL and Media folks are on the thread so can
comment if they are okay with handling this themselves.
Indeed a blanket ban in i915 means no one can try it out later without
further kernel changes.
Regards,
Tvrtko
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