Re: [Intel-gfx] [PATCH v2 14/15] drm/i915/guc: Support OA when Wa_16011777198 is enabled

["Belgaumkar, Vinay" <vinay.belgaumkar@intel.com>]

On 9/26/2022 11:19 AM, Umesh Nerlige Ramappa wrote:
> On Mon, Sep 26, 2022 at 08:56:01AM -0700, Dixit, Ashutosh wrote:
>> On Fri, 23 Sep 2022 13:11:53 -0700, Umesh Nerlige Ramappa wrote:
>>>
>>> From: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
>>
>> Hi Umesh/Vinay,
>>
>>> @@ -3254,6 +3265,24 @@ static int i915_oa_stream_init(struct 
>>> i915_perf_stream *stream,
>>>     intel_engine_pm_get(stream->engine);
>>>     intel_uncore_forcewake_get(stream->uncore, FORCEWAKE_ALL);
>>>
>>> +    /*
>>> +     * Wa_16011777198:dg2: GuC resets render as part of the Wa. 
>>> This causes
>>> +     * OA to lose the configuration state. Prevent this by 
>>> overriding GUCRC
>>> +     * mode.
>>> +     */
>>> +    if (intel_guc_slpc_is_used(&gt->uc.guc) &&
>>> +        intel_uc_uses_guc_rc(&gt->uc) &&
>>
>> Is this condition above correct? E.g. what happens when:
>>
>> a. GuCRC is used but SLPC is not used?

Currently, we have no way to separate out GuC RC and SLPC. Both are on 
when guc submission is enabled/supported. So, the above check is kind of 
redundant anyways.

Thanks,

Vinay.

>> b. GuCRC is not used. Don't we need to disable RC6 in host based RC6
>>   control?
>
> When using host based rc6, existing OA code is using forcewake and a 
> reference to engine_pm to prevent rc6. Other questions, directing to 
> @Vinay.
>
> Thanks,
> Umesh
>
>>
>> Do we need to worry about these cases?
>>
>> Or if we always expect both GuCRC and SLPC to be used on DG2 then I 
>> think
>> let's get rid of these from the if condition and add a drm_err() if 
>> we see
>> these not being used and OA is being enabled on DG2?
>>
>> Thanks.
>> -- 
>> Ashutosh
>>
>>> + (IS_DG2_GRAPHICS_STEP(gt->i915, G10, STEP_A0, STEP_C0) ||
>>> +         IS_DG2_GRAPHICS_STEP(gt->i915, G11, STEP_A0, STEP_B0))) {
>>> +        ret = intel_guc_slpc_override_gucrc_mode(&gt->uc.guc.slpc,
>>> +                             SLPC_GUCRC_MODE_GUCRC_NO_RC6);
>>> +        if (ret) {
>>> +            drm_dbg(&stream->perf->i915->drm,
>>> +                "Unable to override gucrc mode\n");
>>> +            goto err_config;
>>> +        }
>>> +    }
>>> +
>>>     ret = alloc_oa_buffer(stream);
>>>     if (ret)
>>>         goto err_oa_buf_alloc;
>>> -- 
>>> 2.25.1
>>>