[PATCH v8 6/7] drm/xe/xelp: Implement Wa_16010904313

[Tvrtko Ursulin]

On 09/07/2025 00:21, Lucas De Marchi wrote:
> On Thu, Jul 03, 2025 at 09:20:58AM +0100, Tvrtko Ursulin wrote:
>> Add XeLP workaround 16010904313.
>>
>> The description calls for it to be emitted as the indirect context buffer
>> workaround for render and compute, and from the workaround batch buffer
>> for the other engines. Therefore we plug into the previously added
>> respective top level emission functions.
>>
>> The actual command streamer programming sequence differs from what is
>> described in the PRM, in that it assumes the listed LRCA offset was
>> supposed to actually refer to the location of the CTX_TIMESTAMP register
>> instead of LRCA + 0x180c (which is in GPR space). Latter appears to make
>> more sense under the assumption that multiple writes are helping with
>> restoring the CTX_TIMESTAMP register content from the saved context 
>> state.
> 
> I'm requesting a clarification about that to hw/validation. Because this
> doesn't match neither the i915 implementation nor the PRM.

Yep it differs, as discussed before.

Could you also ask about the programming note for INDIRECT_CTX and 
INDIRECT_CTX_OFFSET from the public Tigerlake PRM (Alderlake is not 
available), which says:

"BlitterCS/VideoCS/VideoCS2/VideoEnhancementCS/PositionCS: This register 
functionality is not supported and must not be programmed for these 
command streamers."

I915 does use it, hence I copied it from there, but only now noticed 
this. Maybe that is the reason Wa_16010904313 descriptions calls for the 
wa_bb to be used on !rcs.

Regards,

Tvrtko