Re: [Intel-gfx] [PATCH] drm/i915/tgl: Implement Wa_1606931601

["Srivatsa, Anusha" <anusha.srivatsa@intel.com>]

> -----Original Message-----
> From: Roper, Matthew D <matthew.d.roper@intel.com>
> Sent: Thursday, January 30, 2020 12:43 PM
> To: Srivatsa, Anusha <anusha.srivatsa@intel.com>
> Cc: intel-gfx@lists.freedesktop.org; Ceraolo Spurio, Daniele
> <daniele.ceraolospurio@intel.com>
> Subject: Re: [PATCH] drm/i915/tgl: Implement Wa_1606931601
> 
> On Wed, Jan 29, 2020 at 02:42:06PM -0800, Anusha Srivatsa wrote:
> > Disable Inter and intra Read Suppression (bit 15) and Early Read and
> > Src Swap (bit 14) by setting the chicken register.
> >
> > BSpec: 46045,52890
> >
> > v2: Follow the Bspec implementation for the WA.
> > v3: Have 2 separate defines for bit 14 and 15.
> > - Rename register definitions with TGL_ prefix
> 
> The hardware guys changed their mind again and we're back to only needing
> bit 14 now.  They updated the bspec and the underlying database yet again.
> :-/
 ☹

> >
> > Cc: Matt Roper <matthew.d.roper@intel.com>
> > Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
> > ---
> >  drivers/gpu/drm/i915/gt/intel_workarounds.c | 6 ++++++
> >  drivers/gpu/drm/i915/i915_reg.h             | 2 ++
> >  2 files changed, 8 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > index 5a7db279f702..1f84cd595f88 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > @@ -593,6 +593,12 @@ static void tgl_ctx_workarounds_init(struct
> intel_engine_cs *engine,
> >  	wa_add(wal, FF_MODE2, FF_MODE2_TDS_TIMER_MASK, val,
> >  	       IS_TGL_REVID(engine->i915, TGL_REVID_A0, TGL_REVID_A0) ? 0 :
> >  			    FF_MODE2_TDS_TIMER_MASK);
> > +
> > +	/* Wa_1606931601:tgl */
> > +	WA_SET_BIT_MASKED(GEN7_ROW_CHICKEN2,
> > +			  GEN12_EARLY_READ_SRC0_DISABLE |
> > +
> GEN12_INTER_INTRA_READ_SUPPRESSION_DISABLE);
> 
> I think Daniele already mentioned this on the other discussion, but
> ROW_CHICKEN2 isn't part of the context image on gen12 (see bspec page
> 46255).  This is a change from ICL where it *was* part of the context (see
> bspec page 18907), so even though we handled this register in the
> ctx_workarounds_init for ICL, that's not the appropriate place to put it for
> TGL.
Agreed. 

> Since this isn't a context workaround, we need to determine whether it's a
> general GT workaround (which would be initialized in
> tgl_gt_workarounds_init) or an engine workaround (which would be
> initialized in {rcs,xcs}_engine_wa_init.  In this case the register we're
> modifying is 0xe49c; according to bspec page 52078 this falls in one of the
> forcewake ranges listed under the render engine column (0E000-0E8FF). 

The register we are setting is 0xe4f4. This comes under Render engine. Adding this change to rcs_engine_wa_init().

> So I
> believe in this case that means we want to update
> rcs_engine_wa_init() with this workaround --- that ensures that the
> workaround will be re-applied any time the engine is reset (even if it's not a
> full-GPU reset).
Yes. Adding this to rcs_engine_wa_init().


Anusha 
> 
> Matt
> 
> > +
> >  }
> >
> >  static void
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h
> > b/drivers/gpu/drm/i915/i915_reg.h index 4c72b8ac0f2e..70ead809c706
> > 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -9149,6 +9149,8 @@ enum {
> >  #define   DOP_CLOCK_GATING_DISABLE	(1 << 0)
> >  #define   PUSH_CONSTANT_DEREF_DISABLE	(1 << 8)
> >  #define   GEN11_TDL_CLOCK_GATING_FIX_DISABLE	(1 << 1)
> > +#define   GEN12_EARLY_READ_SRC0_DISABLE		(1 << 14)
> > +#define   GEN12_INTER_INTRA_READ_SUPPRESSION_DISABLE	(1 <<
> 15)
> >
> >  #define HSW_ROW_CHICKEN3		_MMIO(0xe49c)
> >  #define  HSW_ROW_CHICKEN3_L3_GLOBAL_ATOMICS_DISABLE    (1 << 6)
> > --
> > 2.25.0
> >
> 
> --
> Matt Roper
> Graphics Software Engineer
> VTT-OSGC Platform Enablement
> Intel Corporation
> (916) 356-2795
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