[Intel-xe] [PATCH 2/2] drm/xe/xe2: Report number of Xe2 EUs

[Matt Roper]

On Wed, Sep 20, 2023 at 02:21:03PM -0700, Lucas De Marchi wrote:
> With Xe2, one bit in the fuse enables one Xe2 EU.  Note that although
> Bspec 62564 still refers to 1 bit == a pair of EUs, this is about the
> legacy number according to Bspec 70820.

+Cc Jose.

Looking at the bspec history it doesn't appear there's any true hardware
change here; this is just a terminology change that someone thought
would make the bspec more clear (so they added "legacy" to the true
hardware count to distinguish it from the fuse register, and then later
came back and added a separate "Num EU" column that matches fuse
register).  And it seems that this attempted terminology change wasn't
even handled consistently across various platforms.  The equivalent
bspec pages for most other platforms are still giving only the "legacy"
numbers, either with or without the "legacy" label in the text.

But regardless of which terminology is actually more/less confusing on
that bspec page, what really matters is what our userspace partners
want.  If we want to change the uapi from reporting the true hardware
value to reporting the fusing number, we should coordinate that
behavioral change with them.  And if they're trying to access
hardware-level ("legacy") EUs independently anywhere and can't just
operate on pairs, then such a change may not be possible.


Matt

> 
> Bspec: 70820, 70821, 62564
> Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
> ---
>  drivers/gpu/drm/xe/xe_gt_topology.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_topology.c b/drivers/gpu/drm/xe/xe_gt_topology.c
> index 011ad7f2325c..878f3ed7bc26 100644
> --- a/drivers/gpu/drm/xe/xe_gt_topology.c
> +++ b/drivers/gpu/drm/xe/xe_gt_topology.c
> @@ -49,8 +49,8 @@ load_eu_mask(struct xe_gt *gt, xe_eu_mask_t mask)
>  	if (GRAPHICS_VERx100(xe) < 1250)
>  		reg_val = ~reg_val & XELP_EU_MASK;
>  
> -	/* On PVC, one bit = one EU */
> -	if (GRAPHICS_VERx100(xe) == 1260) {
> +	if (GRAPHICS_VERx100(xe) >= 2000 || GRAPHICS_VERx100(xe) == 1260) {
> +		/* One bit == one EU */
>  		val = reg_val;
>  	} else {
>  		/* All other platforms, one bit = 2 EU */
> -- 
> 2.40.1
> 

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