Re: [Intel-gfx] [PATCH v17 1/1] drm/i915: Allow user to set cache at BO creation

[Andi Shyti <andi.shyti@linux.intel.com>]

Hi Carl,

On Wed, Jun 07, 2023 at 03:40:20AM +0000, Zhang, Carl wrote:
> Media driver reverted previous patches, and file a new  PR
> https://github.com/intel/media-driver/pull/1680
> will hold this PR until the uapi changes appear in drm_next.

That's great, thanks a lot for the quick actions here.

Before pushing I am going to replace the Media part in the commit
log with the following sentence:

"
The media driver supprt has bin submitted in this merge request:
https://github.com/intel/media-driver/pull/1680
"

> besides this, ask a dumb question. 
> How we retrieve the pat_index from a shared resource though dma_buf fd?
> maybe we need to know whether it could be CPU cached if we want map it.
> Of course, looks there are no real usage to access it though CPU. 
> Just use it directly without any pat related options ?

I am not understanding. Do you want to ask the PAT table to the
driver? Are you referring to the CPU PAT index?

In any case, if I understood correctly, you don't necessarily
always need to set the PAT options and the cache options will
fall into the default values.

Please let me know if I haven't answered the question.

Andi

> Thanks
> Carl
> 
> > -----Original Message-----
> > From: Andi Shyti <andi.shyti@linux.intel.com>
> > Sent: Tuesday, June 6, 2023 7:15 PM
> > To: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> > Cc: Andi Shyti <andi.shyti@linux.intel.com>; Tvrtko Ursulin
> > <tvrtko.ursulin@linux.intel.com>; Yang, Fei <fei.yang@intel.com>; Chris
> > Wilson <chris@chris-wilson.co.uk>; Roper, Matthew D
> > <matthew.d.roper@intel.com>; Justen, Jordan L <jordan.l.justen@intel.com>;
> > Zhang, Carl <carl.zhang@intel.com>; Gu, Lihao <lihao.gu@intel.com>; Intel
> > GFX <intel-gfx@lists.freedesktop.org>; DRI Devel <dri-
> > devel@lists.freedesktop.org>
> > Subject: Re: [PATCH v17 1/1] drm/i915: Allow user to set cache at BO creation
> > 
> > > > > > To comply with the design that buffer objects shall have
> > > > > > immutable cache setting through out their life cycle, {set,
> > > > > > get}_caching ioctl's are no longer supported from MTL onward.
> > > > > > With that change caching policy can only be set at object
> > > > > > creation time. The current code applies a default (platform dependent)
> > cache setting for all objects.
> > > > > > However this is not optimal for performance tuning. The patch
> > > > > > extends the existing gem_create uAPI to let user set PAT index
> > > > > > for the object at creation time.
> > > > > > The new extension is platform independent, so UMD's can switch
> > > > > > to using this extension for older platforms as well, while {set,
> > > > > > get}_caching are still supported on these legacy paltforms for
> > compatibility reason.
> > > > > > However, since PAT index was not clearly defined for platforms
> > > > > > prior to
> > > > > > GEN12 (TGL), so we are limiting this externsion to GEN12+
> > > > > > platforms only. See ext_set_pat() in for the implementation details.
> > > > > >
> > > > > > Note: The documentation related to the PAT/MOCS tables is
> > > > > > currently available for Tiger Lake here:
> > > > > > https://www.intel.com/content/www/us/en/docs/graphics-for-linux/
> > > > > > developer-reference/1-0/tiger-lake.html
> > > > > >
> > > > > > BSpec: 45101
> > > > > >
> > > > > > Mesa support has been submitted in this merge request:
> > > > > > https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22878
> > > > > >
> > > > > > The media driver is supported by the following commits:
> > > > > > https://github.com/intel/media-
> > driver/commit/92c00a857433ebb34ec
> > > > > > 575e9834f473c6fcb6341
> > > > > > https://github.com/intel/media-driver/commit/fd375cf2c5e1f6bf6b4
> > > > > > 3258ff797b3134aadc9fd
> > > > > > https://github.com/intel/media-
> > driver/commit/08dd244b22484770a33
> > > > > > 464c2c8ae85430e548000
> > >
> > > Andi, let's still get these corrected before merging once the
> > > media-driver revert is completed.
> > 
> > Sure!
> > 
> > At least this doesn't need a new version to be respinned.
> > 
> > Please, Carl, link the new pull request and I will update the commit log.
> > 
> > Andi