[Intel-gfx] [PATCH] drm/i915/icl: Apply WaEnablePreemptionGranularityControlByUMD

[Joonas Lahtinen]

+ Ken/Jason for Mesa

Quoting Matt Roper (2019-01-07 21:19:31)
> On Mon, Jan 07, 2019 at 01:23:50PM +0100, Michał Winiarski wrote:
> > On Mon, Jan 07, 2019 at 01:01:16PM +0200, Joonas Lahtinen wrote:
> > > Quoting José Roberto de Souza (2019-01-04 19:37:00)
> > > > According to Workaround database ICL also needs
> > > > WaEnablePreemptionGranularityControlByUMD, to allow userspace to do
> > > > fine-granularity preemptions per-context.
> > > 
> > > I must wonder where is the userspace component that needs this, and why
> > > it hasn't been noticed earlier?
> > > 
> > > Or is this one more of the cases when no userspace actually uses the
> > > register?
> > 
> > It's used:
> > https://gitlab.freedesktop.org/mesa/mesa/blob/master/src/mesa/drivers/dri/i965/brw_state_upload.c#L64
> > 
> > -Michał
> 
> Wasn't this just an artificial i915-only workaround that was added to
> prevent breakage of pre-preemption UMD's?  Initial gen9 driver releases
> didn't support preemption, so when preemption support did get added to
> i915, the kernel had to force object-level off by default at context
> creation to avoid breaking old userspace that didn't build batch buffers
> with all the necessary preemption workarounds.  This CS_CHICKEN1
> register was then exposed to userspace so that newer, preemption-aware
> userspace could opt back in if it properly supported preemption.
> 
> For gen11, there shouldn't be any "old" userspace around that doesn't
> support preemption, so shouldn't the kernel just leave object-level
> preemption enabled by default (meaning there's no need to expose this
> register to userspace to allow it to explicitly opt-in)?

Makes sense to me. We should have known by know if somebody expects to
control the register, because they would be failing to do so.

Mesa could also drop the register load for Gen11+

Regards, Joonas

> 
> Matt
> 
> > 
> > > Regards, Joonas
> > > 
> > > > 
> > > > BSpec: 11348
> > > > Cc: Oscar Mateo <oscar.mateo at intel.com>
> > > > Cc: Radhakrishna Sripada <radhakrishna.sripada at intel.com>
> > > > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > > > ---
> > > >  drivers/gpu/drm/i915/intel_workarounds.c | 9 ++++++---
> > > >  1 file changed, 6 insertions(+), 3 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/intel_workarounds.c b/drivers/gpu/drm/i915/intel_workarounds.c
> > > > index 480c53a2ecb5..bbc5a66faa07 100644
> > > > --- a/drivers/gpu/drm/i915/intel_workarounds.c
> > > > +++ b/drivers/gpu/drm/i915/intel_workarounds.c
> > > > @@ -1014,7 +1014,7 @@ static void gen9_whitelist_build(struct i915_wa_list *w)
> > > >         /* WaVFEStateAfterPipeControlwithMediaStateClear:skl,bxt,glk,cfl */
> > > >         whitelist_reg(w, GEN9_CTX_PREEMPT_REG);
> > > >  
> > > > -       /* WaEnablePreemptionGranularityControlByUMD:skl,bxt,kbl,cfl,[cnl] */
> > > > +       /* WaEnablePreemptionGranularityControlByUMD:skl,bxt,kbl,cfl,[cnl,icl] */
> > > >         whitelist_reg(w, GEN8_CS_CHICKEN1);
> > > >  
> > > >         /* WaAllowUMDToModifyHDCChicken1:skl,bxt,kbl,glk,cfl */
> > > > @@ -1068,6 +1068,9 @@ static void icl_whitelist_build(struct i915_wa_list *w)
> > > >  
> > > >         /* WaAllowUMDToModifySamplerMode:icl */
> > > >         whitelist_reg(w, GEN10_SAMPLER_MODE);
> > > > +
> > > > +       /* WaEnablePreemptionGranularityControlByUMD:icl */
> > > > +       whitelist_reg(w, GEN8_CS_CHICKEN1);
> > > >  }
> > > >  
> > > >  void intel_engine_init_whitelist(struct intel_engine_cs *engine)
> > > > @@ -1186,8 +1189,8 @@ static void rcs_engine_wa_init(struct intel_engine_cs *engine)
> > > >                                     GEN7_DISABLE_SAMPLER_PREFETCH);
> > > >         }
> > > >  
> > > > -       if (IS_GEN(i915, 9) || IS_CANNONLAKE(i915)) {
> > > > -               /* WaEnablePreemptionGranularityControlByUMD:skl,bxt,kbl,cfl,cnl */
> > > > +       if (IS_GEN_RANGE(i915, 9, 11)) {
> > > > +               /* WaEnablePreemptionGranularityControlByUMD:skl,bxt,kbl,cfl,cnl,icl */
> > > >                 wa_masked_en(wal,
> > > >                              GEN7_FF_SLICE_CS_CHICKEN1,
> > > >                              GEN9_FFSC_PERCTX_PREEMPT_CTRL);
> > > > -- 
> > > > 2.20.1
> > > > 
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> 
> -- 
> Matt Roper
> Graphics Software Engineer
> IoTG Platform Enabling & Development
> Intel Corporation
> (916) 356-2795