[PATCH v2 4/5] drm/xe: Assign GT IDs properly on multi-tile + multi-GT platforms

[Matt Roper]

On Wed, Jun 25, 2025 at 05:11:27PM +0530, Vodapalli, Ravi Kumar wrote:
> 
> 
> On 6/17/2025 7:39 AM, Matt Roper wrote:
> > Although "multi-tile" and "multiple GTs per tile" are mutually-exclusive
> > characteristics on all of our platforms today, this may not always be
> > true.  Assign GT IDs according to xe->info.max_gt_per_tile in a way that
> > should work even if future platforms have different configurations.
> > 
> > This patch should not change the behavior of current platforms; it only
> > future-proofs for potential future designs.
> > 
> > Signed-off-by: Matt Roper<matthew.d.roper at intel.com>
> > ---
> >   drivers/gpu/drm/xe/xe_mmio.c |  8 --------
> >   drivers/gpu/drm/xe/xe_pci.c  | 14 ++++----------
> >   2 files changed, 4 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
> > index 7357458bc0d2..b65d888ee8e4 100644
> > --- a/drivers/gpu/drm/xe/xe_mmio.c
> > +++ b/drivers/gpu/drm/xe/xe_mmio.c
> > @@ -82,14 +82,6 @@ static void mmio_multi_tile_setup(struct xe_device *xe, size_t tile_mmio_size)
> >   			drm_info(&xe->drm, "tile_count: %d, reduced_tile_count %d\n",
> >   				 xe->info.tile_count, tile_count);
> >   			xe->info.tile_count = tile_count;
> > -
> > -			/*
> > -			 * FIXME: Needs some work for standalone media, but
> > -			 * should be impossible with multi-tile for now:
> > -			 * multi-tile platform with standalone media doesn't
> > -			 * exist
> > -			 */
> > -			xe->info.gt_count = xe->info.tile_count;
> >   		}
> >   	}
> > diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
> > index a4885f64c2c4..b29252abbf3e 100644
> > --- a/drivers/gpu/drm/xe/xe_pci.c
> > +++ b/drivers/gpu/drm/xe/xe_pci.c
> > @@ -687,10 +687,11 @@ static int xe_info_init(struct xe_device *xe,
> >   	 */
> >   	for_each_tile(tile, xe, id) {
> >   		gt = tile->primary_gt;
> > -		gt->info.id = xe->info.gt_count++;
> >   		gt->info.type = XE_GT_TYPE_MAIN;
> > +		gt->info.id = tile->id * xe->info.max_gt_per_tile;
> why gt->info.id is equal to tile->id * xe->info.max_gt_per_tile then the
> resultant number exceeds max_gt_per_tile , i dont know whether we can assign
> gt->info.id as equal to tile->id

Yes, this is correct.  Supposed a future platform has four types of GTs:
primary, media, foo, and bar.  That platform would have max_gt_per_tile
set to 4.  Also supposed that the same future platform has three tiles.
In this example, the overall possible GT IDs in the system would be
assigned as:

   0:  tile 0 primary 
   1:  tile 0 media
   2:  tile 0 foo
   3:  tile 0 bar
   4:  tile 1 primary 
   5:  tile 1 media
   6:  tile 1 foo
   7:  tile 1 bar
   8:  tile 2 primary 
   9:  tile 2 media
  10:  tile 2 foo
  11:  tile 2 bar

So the GT ID for a specific tile's GTs are:

  primary:  tile ID * max_gt_per_tile + 0
  media:    tile ID * max_gt_per_tile + 1
  foo:      tile ID * max_gt_per_tile + 2
  bar:      tile ID * max_gt_per_tile + 3


Some of these GTs may or may not exist depending on fusing or other
platform details; userspace uses the GT query ioctl to discover the
available GTs.  It might see something from the query interface like:

  (GT0 primary, GT1 media, GT3 bar, GT4 primary, GT6 foo, GT8 primary)

meaning there are 6 usable GTs in the system, and the IDs "skip" some
numbers for cases where a GT does not exist.


Matt


> >   		gt->info.has_indirect_ring_state = graphics_desc->has_indirect_ring_state;
> >   		gt->info.engine_mask = graphics_desc->hw_engine_mask;
> > +		xe->info.gt_count++;
> >   		if (MEDIA_VER(xe) < 13 && media_desc)
> >   			gt->info.engine_mask |= media_desc->hw_engine_mask;
> > @@ -708,17 +709,10 @@ static int xe_info_init(struct xe_device *xe,
> >   		gt = tile->media_gt;
> >   		gt->info.type = XE_GT_TYPE_MEDIA;
> > +		gt->info.id = tile->id * xe->info.max_gt_per_tile + 1;
> >   		gt->info.has_indirect_ring_state = media_desc->has_indirect_ring_state;
> >   		gt->info.engine_mask = media_desc->hw_engine_mask;
> > -
> > -		/*
> > -		 * FIXME: At the moment multi-tile and standalone media are
> > -		 * mutually exclusive on current platforms.  We'll need to
> > -		 * come up with a better way to number GTs if we ever wind
> > -		 * up with platforms that support both together.
> > -		 */
> > -		drm_WARN_ON(&xe->drm, id != 0);
> > -		gt->info.id = xe->info.gt_count++;
> > +		xe->info.gt_count++;
> >   	}
> >   	return 0;

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