[Intel-xe] [PATCH] drm/xe : Fix GT looping for standalone media

[Matt Roper]

On Tue, Jun 13, 2023 at 03:12:32PM +0530, Riana Tauro wrote:
> Currently the id of primary gt is set using gt_count and not
> the media gt.
> 
> set gt->info.id of media gt using gt_count
> 
> Signed-off-by: Riana Tauro <riana.tauro at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_pci.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
> index bd1f59b49928..2991cf5365d5 100644
> --- a/drivers/gpu/drm/xe/xe_pci.c
> +++ b/drivers/gpu/drm/xe/xe_pci.c
> @@ -590,7 +590,7 @@ static int xe_info_init(struct xe_device *xe,
>  		 * up with platforms that support both together.
>  		 */
>  		drm_WARN_ON(&xe->drm, id != 0);
> -		gt->info.id = 1;
> +		gt->info.id = xe->info.gt_count++;

1 is always correct today since MTL is the only platform with a
standalone media GT, and it's a single-tile platform (so the GTs are
0/1).  This will also be true for any future single-tile platforms with
standalone media.

If/when we eventually have a platform that's both multi-tile _and_
multi-gt, we need to decide how we're going to identify GTs.  Since no
such platform exists today, we also don't know for sure whether every
tile will have both GTs, or whether only some of the tiles will have
multiple GTs.  It's not clear that using gt_count++ will necessarily be
the right thing to do; maybe we want to make primary GTs 2*tile and
media GTs 2*tile+1 (i.e., intentionally skip IDs if some of the tiles
have both and others do not).  We may also want to adjust how we
approach GT identification in the uapi in general --- maybe we don't
even want to give GTs a global ID anymore and instead want to move
toward identifying GT with a (tile_id, gt_id) tuple where gt_id is an
intra-tile number (i.e., 0=primary, 1=media).

The current GT and tile series aimed to just preserve the existing uapi
without changes, and using an ID of 1 for media (with all the FIXME
comments in the code) does that for now.  But sometime soon we do need
to make a formal decision on exactly how we want to work with tiles and
GTs in the uapi, going forward and that needs to be something that we
loop in our userspace partners on; we can't just make the decision
ourselves on the kernel side.


Matt

>  	}
>  
>  	return 0;
> -- 
> 2.40.0
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation