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

[Dixit, Ashutosh]

On Tue, 27 Sep 2022 10:34:52 -0700, Dixit, Ashutosh wrote:
>
> On Tue, 27 Sep 2022 09:11:23 -0700, Umesh Nerlige Ramappa wrote:
> >
> > On Mon, Sep 26, 2022 at 04:28:44PM -0700, Dixit, Ashutosh wrote:
> > > On Mon, 26 Sep 2022 14:17:21 -0700, Belgaumkar, Vinay wrote:
> > >>
> > >>
> > >> 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 at 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.
> > >
> > > That is why I was suggesting changing the if check to an assert or
> > > drm_err. So looks like it will work with or without GuC RC, but if we are
> > > using GuC RC we should be using SLPC. So:
> > >
> > >	if (GuC_RC && !SLPC)
> > >		drm_err();
> >
> > I am little confused. What's the ask here? Should I just use one of these
> > conditions? i.e.
> >
> > if (intel_guc_slpc_is_used(&gt->uc.guc))
>
> I think let's just use intel_uc_uses_guc_rc and drop
> intel_guc_slpc_is_used. I am assuming if SLPC is somehow not on and we try
> to use SLPC set/unset param, some kind of error will be reported.

With the above this patch is also:

Reviewed-by: Ashutosh Dixit <ashutosh.dixit at intel.com>

>
>
> > ...
> >
> > Thanks,
> > Umesh
> >
> > >
> > >> 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
> > >> >>>