[PATCH] drm/xe/guc: Enable WA_DUAL_QUEUE for newer platforms

[Daniele Ceraolo Spurio]

On 12/11/2024 10:56 AM, Cavitt, Jonathan wrote:
> -----Original Message-----
> From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of Daniele Ceraolo Spurio
> Sent: Tuesday, November 26, 2024 5:11 PM
> To: intel-xe at lists.freedesktop.org
> Cc: Ceraolo Spurio, Daniele <daniele.ceraolospurio at intel.com>; Harrison, John C <john.c.harrison at intel.com>
> Subject: [PATCH] drm/xe/guc: Enable WA_DUAL_QUEUE for newer platforms
>> The DUAL_QUEUE_WA tells the GuC to not allow concurrent submissions
>> on RCS and CCSes with different address spaces, which on DG2 is
>> required as a WA for an HW bug. On newer platforms, this block has
>> been moved in HW at the CS level, by stalling the RCS/CCS context
>> switch when one of the other RCS/CCSes is busy with a different
>> address space. While functionally correct, having a submission
>> stalled on the HW limits the GuC ability to shuffle things around and
>> can cause complications if the non-stalled submission runs for a long
>> time, because the GuC doesn't know that the stalled submission isn't
>> actually running and might declare it as hung. Therefore, we enable
>> the DUAL_QUEUE_WA on all newer platforms to move management back to
>> the GuC.
>>
>> Note that the GuC specs also recommend enabling this for all platforms
>> starting from MTL that have a CCS.
>>
>> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
>> Cc: John Harrison <John.C.Harrison at Intel.com>
>> ---
>>   drivers/gpu/drm/xe/xe_guc.c | 16 +++++++++++++++-
>>   1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/xe/xe_guc.c b/drivers/gpu/drm/xe/xe_guc.c
>> index df1ba94cf4ca..ddbfbdf901b0 100644
>> --- a/drivers/gpu/drm/xe/xe_guc.c
>> +++ b/drivers/gpu/drm/xe/xe_guc.c
>> @@ -151,7 +151,21 @@ static u32 guc_ctl_wa_flags(struct xe_guc *guc)
>>   	if (XE_WA(gt, 14014475959))
>>   		flags |= GUC_WA_HOLD_CCS_SWITCHOUT;
>>   
>> -	if (XE_WA(gt, 22011391025))
>> +	/*
>> +	 * The DUAL_QUEUE_WA tells the GuC to not allow concurrent submissions
>> +	 * on RCS and CCSes with different address spaces, which on DG2 is
>> +	 * required as a WA for an HW bug. On newer platforms, this block has
>> +	 * been moved in HW at the CS level, by stalling the RCS/CCS context
>> +	 * switch when one of the other RCS/CCSes is busy with a different
>> +	 * address space. While functionally correct, having a submission
>> +	 * stalled on the HW limits the GuC ability to shuffle things around and
>> +	 * can cause complications if the non-stalled submission runs for a long
>> +	 * time, because the GuC doesn't know that the stalled submission isn't
>> +	 * actually running and might declare it as hung. Therefore, we enable
>> +	 * the DUAL_QUEUE_WA on all newer platforms to move management back to
>> +	 * the GuC.
>> +	 */
>> +	if (XE_WA(gt, 22011391025) || GRAPHICS_VERx100(xe) >= 1270)
> This is acceptable, and preliminary testing shows that this fix will repair
> several observed issues.  Though I'm a bit confused why we aren't adding
> the additional graphics version check to the workaround itself?
>
> Is it because the workaround implies a hardware problem, whereas the
> additional applications we're applying it to here are not related to hardware-
> specific limitations/issues?  I think it's a bit odd to make such a distinction,
> but that's just my opinion I won't block on it.

Yes. The wa_oob.rules file matches what's in the WA database, so I 
didn't want to add anything there that wasn't reflected in the database.

>
> Regardless of if we decide to keep this implementation or merge the check into
> xe_wa_oob.rules:
> Reviewed-by: Jonathan Cavitt <jonathan.cavitt at intel.com>

Thanks! I'm going to do a respin of this to not apply the flag to the 
media GT, will cc you on it.

Daniele

> By the way, this patch was also separately reviewed by Jesus Narvaez, so
> don't forget to add their RB in as well.
> -Jonathan Cavitt
>
>>   		flags |= GUC_WA_DUAL_QUEUE;
>>   
>>   	/*
>> -- 
>> 2.43.0
>>
>>