[PATCH 1/2] drm/xe: Probe for tile count during device info initialization

[Cavitt, Jonathan]

-----Original Message-----
From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of Gustavo Sousa
Sent: Wednesday, July 23, 2025 1:20 PM
To: intel-xe at lists.freedesktop.org
Cc: Sousa, Gustavo <gustavo.sousa at intel.com>
Subject: [PATCH 1/2] drm/xe: Probe for tile count during device info initialization
> 
> The function mmio_multi_tile_setup() does not look like the proper
> location for probing for the number of existing tiles in the hardware.
> It should not be that function's responsibility and such information
> should instead be already available when it gets called.
> 
> The fact that we need to adjust gt_count is a symptom of that.
> 
> Move probing of available tile count to a dedicated function named
> xe_info_probe_tile_count() and call it from xe_info_init(), which seems
> like a more appropriate place for that.
> 
> With that move, we don't need and should not adjust gt_count anymore,
> because the function gets called before the original initialization of
> that field.

I'd maybe reword this sentence to say something like:

"""
With that move, we no longer need to adjust gt_count as a part of the
xe_info_probe_tile_count function, as that field will be initialized later
in xe_info_init anyway.
"""

But other than that:
Reviewed-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
-Jonathan Cavitt

> 
> Signed-off-by: Gustavo Sousa <gustavo.sousa at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_mmio.c | 33 ---------------------------------
>  drivers/gpu/drm/xe/xe_pci.c  | 32 ++++++++++++++++++++++++++++++++
>  2 files changed, 32 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
> index e4db8d58ea2d..ef6f3ea573a2 100644
> --- a/drivers/gpu/drm/xe/xe_mmio.c
> +++ b/drivers/gpu/drm/xe/xe_mmio.c
> @@ -58,7 +58,6 @@ static void tiles_fini(void *arg)
>  static void mmio_multi_tile_setup(struct xe_device *xe, size_t tile_mmio_size)
>  {
>  	struct xe_tile *tile;
> -	struct xe_gt *gt;
>  	u8 id;
>  
>  	/*
> @@ -68,38 +67,6 @@ static void mmio_multi_tile_setup(struct xe_device *xe, size_t tile_mmio_size)
>  	if (xe->info.tile_count == 1)
>  		return;
>  
> -	/* Possibly override number of tile based on configuration register */
> -	if (!xe->info.skip_mtcfg) {
> -		struct xe_mmio *mmio = xe_root_tile_mmio(xe);
> -		u8 tile_count, gt_count;
> -		u32 mtcfg;
> -
> -		/*
> -		 * Although the per-tile mmio regs are not yet initialized, this
> -		 * is fine as it's going to the root tile's mmio, that's
> -		 * guaranteed to be initialized earlier in xe_mmio_probe_early()
> -		 */
> -		mtcfg = xe_mmio_read32(mmio, XEHP_MTCFG_ADDR);
> -		tile_count = REG_FIELD_GET(TILE_COUNT, mtcfg) + 1;
> -
> -		if (tile_count < xe->info.tile_count) {
> -			drm_info(&xe->drm, "tile_count: %d, reduced_tile_count %d\n",
> -				 xe->info.tile_count, tile_count);
> -			xe->info.tile_count = tile_count;
> -
> -			/*
> -			 * We've already setup gt_count according to the full
> -			 * tile count.  Re-calculate it to only include the GTs
> -			 * that belong to the remaining tile(s).
> -			 */
> -			gt_count = 0;
> -			for_each_gt(gt, xe, id)
> -				if (gt->info.id < tile_count * xe->info.max_gt_per_tile)
> -					gt_count++;
> -			xe->info.gt_count = gt_count;
> -		}
> -	}
> -
>  	for_each_remote_tile(tile, xe, id)
>  		xe_mmio_init(&tile->mmio, tile, xe->mmio.regs + id * tile_mmio_size, SZ_4M);
>  }
> diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
> index f4ea13527945..4f5d4f0a8173 100644
> --- a/drivers/gpu/drm/xe/xe_pci.c
> +++ b/drivers/gpu/drm/xe/xe_pci.c
> @@ -17,6 +17,7 @@
>  
>  #include "display/xe_display.h"
>  #include "regs/xe_gt_regs.h"
> +#include "regs/xe_regs.h"
>  #include "xe_device.h"
>  #include "xe_drv.h"
>  #include "xe_gt.h"
> @@ -603,6 +604,35 @@ static int xe_info_init_early(struct xe_device *xe,
>  	return 0;
>  }
>  
> +/*
> + * Possibly override number of tile based on configuration register.
> + */
> +static void xe_info_probe_tile_count(struct xe_device *xe)
> +{
> +	struct xe_mmio *mmio;
> +	u8 tile_count;
> +	u32 mtcfg;
> +
> +	if (xe->info.skip_mtcfg)
> +		return;
> +
> +	mmio = xe_root_tile_mmio(xe);
> +
> +	/*
> +	 * Although the per-tile mmio regs are not yet initialized, this
> +	 * is fine as it's going to the root tile's mmio, that's
> +	 * guaranteed to be initialized earlier in xe_mmio_probe_early()
> +	 */
> +	mtcfg = xe_mmio_read32(mmio, XEHP_MTCFG_ADDR);
> +	tile_count = REG_FIELD_GET(TILE_COUNT, mtcfg) + 1;
> +
> +	if (tile_count < xe->info.tile_count) {
> +		drm_info(&xe->drm, "tile_count: %d, reduced_tile_count %d\n",
> +			 xe->info.tile_count, tile_count);
> +		xe->info.tile_count = tile_count;
> +	}
> +}
> +
>  /*
>   * Initialize device info content that does require knowledge about
>   * graphics / media IP version.
> @@ -677,6 +707,8 @@ static int xe_info_init(struct xe_device *xe,
>  	xe->info.has_usm = graphics_desc->has_usm;
>  	xe->info.has_64bit_timestamp = graphics_desc->has_64bit_timestamp;
>  
> +	xe_info_probe_tile_count(xe);
> +
>  	for_each_remote_tile(tile, xe, id) {
>  		int err;
>  
> 
> -- 
> 2.50.1
> 
>