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

[Lucas De Marchi]

On Wed, Sep 20, 2023 at 02:50:55PM -0700, Matt Roper wrote:
>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

it's being called "Xe2 EU" now

>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.

like any rename change in doc or bspec?

>
>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

it's not just about reporting the fuse, it's about reporting the Xe2 EU
count... I don't think it's really an UAPI change - this is being done
to Xe2, we can't really change older platforms (not that it really
matters for the Xe driver, but I think it's best to keep the older
platforms as is).

>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.

I pinged all the UMDs as if this was a UAPI change and pointed to this
thread for them to chime in.

Lucas De Marchi

>
>
>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