Re: [PATCH v2 2/3] drm/i915/mtl: Correct implementation of Wa_18018781329

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On Wed, Jan 25, 2023 at 03:43:26PM -0800, Matt Roper wrote:
> On Wed, Jan 25, 2023 at 03:41:58PM -0800, Matt Roper wrote:
> > Workaround Wa_18018781329 has applied to several recent Xe_HP-based
> > platforms.  However there are some extra gotchas to implementing this
> > properly for MTL that we need to take into account:
> > 
> >  * Due to the separation of media and render/compute into separate GTs,
> >    this workaround needs to be implemented on each GT, not just the
> >    primary GT.  Since each class of register only exists on one of the
> >    two GTs, we should program the appropriate registers on each GT.
> > 
> >  * As with past Xe_HP platforms, the registers on the primary GT (Xe_LPG
> >    IP) are multicast/replicated registers and should be handled with the
> >    MCR-aware functions.  However the registers on the media GT (Xe_LPM+
> >    IP) are regular singleton registers and should _not_ use MCR
> >    handling.  We need to create separate register definitions for the
> >    Xe_HP multicast form and the Xe_LPM+ singleton form and use each in
> >    the appropriate place.
> > 
> >  * Starting with MTL, workarounds documented by the hardware teams are
> >    technically associated with IP versions/steppings rather than
> >    top-level platforms.  That means we should take care to check the
> >    media IP version rather than the graphics IP version when deciding
> >    whether the workaround is needed on the Xe_LPM+ media GT (in this
> >    case the workaround applies to both IPs and the stepping bounds are
> >    identical, but we should still write the code appropriately to set a
> >    proper precedent for future workaround implementations).
> > 
> >  * It's worth noting that the GSC register and the CCS register are
> >    defined with the same MMIO offset (0xCF30).  Since the CCS is only
> >    relevant to the primary GT and the GSC is only relevant to the media
> >    GT there isn't actually a clash here (the media GT automatically adds
> >    the additional 0x380000 GSI offset).  However there's currently a
> >    glitch in the bspec where the CCS register doesn't show up at all and
> >    the GSC register is listed as existing on both GTs.  That's a known
> >    documentation problem for several registers with shared GSC/CCS
> >    offsets; rest assured that the CCS register really does still exist.
> > 
> > Cc: Gustavo Sousa <gustavo.sousa@xxxxxxxxx>
> > Signed-off-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
> 
> Forgot to add:
> 
> Fixes: 41bb543f5598 ("drm/i915/mtl: Add initial gt workarounds")
> 

Reviewed-by: Gustavo Sousa <gustavo.sousa@xxxxxxxxx>

> 
> Matt
> 
> > ---
> >  drivers/gpu/drm/i915/gt/intel_gt_regs.h     |  7 +++++--
> >  drivers/gpu/drm/i915/gt/intel_workarounds.c | 22 ++++++++++++++-------
> >  drivers/gpu/drm/i915/i915_drv.h             |  4 ++++
> >  3 files changed, 24 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> > index 2727645864db..310bdde049ab 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> > @@ -1100,8 +1100,11 @@
> >  #define XEHP_MERT_MOD_CTRL			MCR_REG(0xcf28)
> >  #define RENDER_MOD_CTRL				MCR_REG(0xcf2c)
> >  #define COMP_MOD_CTRL				MCR_REG(0xcf30)
> > -#define VDBX_MOD_CTRL				MCR_REG(0xcf34)
> > -#define VEBX_MOD_CTRL				MCR_REG(0xcf38)
> > +#define XELPMP_GSC_MOD_CTRL			_MMIO(0xcf30)	/* media GT only */
> > +#define XEHP_VDBX_MOD_CTRL			MCR_REG(0xcf34)
> > +#define XELPMP_VDBX_MOD_CTRL			_MMIO(0xcf34)
> > +#define XEHP_VEBX_MOD_CTRL			MCR_REG(0xcf38)
> > +#define XELPMP_VEBX_MOD_CTRL			_MMIO(0xcf38)
> >  #define   FORCE_MISS_FTLB			REG_BIT(3)
> >  
> >  #define GEN12_GAMSTLB_CTRL			_MMIO(0xcf4c)
> > diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > index 9db60078460a..4c978abf3e2a 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> > @@ -1681,8 +1681,8 @@ dg2_gt_workarounds_init(struct intel_gt *gt, struct i915_wa_list *wal)
> >  	/* Wa_18018781329 */
> >  	wa_mcr_write_or(wal, RENDER_MOD_CTRL, FORCE_MISS_FTLB);
> >  	wa_mcr_write_or(wal, COMP_MOD_CTRL, FORCE_MISS_FTLB);
> > -	wa_mcr_write_or(wal, VDBX_MOD_CTRL, FORCE_MISS_FTLB);
> > -	wa_mcr_write_or(wal, VEBX_MOD_CTRL, FORCE_MISS_FTLB);
> > +	wa_mcr_write_or(wal, XEHP_VDBX_MOD_CTRL, FORCE_MISS_FTLB);
> > +	wa_mcr_write_or(wal, XEHP_VEBX_MOD_CTRL, FORCE_MISS_FTLB);
> >  
> >  	/* Wa_1509235366:dg2 */
> >  	wa_write_or(wal, GEN12_GAMCNTRL_CTRL,
> > @@ -1700,8 +1700,8 @@ pvc_gt_workarounds_init(struct intel_gt *gt, struct i915_wa_list *wal)
> >  	/* Wa_18018781329 */
> >  	wa_mcr_write_or(wal, RENDER_MOD_CTRL, FORCE_MISS_FTLB);
> >  	wa_mcr_write_or(wal, COMP_MOD_CTRL, FORCE_MISS_FTLB);
> > -	wa_mcr_write_or(wal, VDBX_MOD_CTRL, FORCE_MISS_FTLB);
> > -	wa_mcr_write_or(wal, VEBX_MOD_CTRL, FORCE_MISS_FTLB);
> > +	wa_mcr_write_or(wal, XEHP_VDBX_MOD_CTRL, FORCE_MISS_FTLB);
> > +	wa_mcr_write_or(wal, XEHP_VEBX_MOD_CTRL, FORCE_MISS_FTLB);
> >  }
> >  
> >  static void
> > @@ -1715,8 +1715,6 @@ xelpg_gt_workarounds_init(struct intel_gt *gt, struct i915_wa_list *wal)
> >  		/* Wa_18018781329 */
> >  		wa_mcr_write_or(wal, RENDER_MOD_CTRL, FORCE_MISS_FTLB);
> >  		wa_mcr_write_or(wal, COMP_MOD_CTRL, FORCE_MISS_FTLB);
> > -		wa_mcr_write_or(wal, VDBX_MOD_CTRL, FORCE_MISS_FTLB);
> > -		wa_mcr_write_or(wal, VEBX_MOD_CTRL, FORCE_MISS_FTLB);
> >  	}
> >  
> >  	/*
> > @@ -1729,7 +1727,17 @@ xelpg_gt_workarounds_init(struct intel_gt *gt, struct i915_wa_list *wal)
> >  static void
> >  xelpmp_gt_workarounds_init(struct intel_gt *gt, struct i915_wa_list *wal)
> >  {
> > -	/* FIXME: Actual workarounds will be added in future patch(es) */
> > +	if (IS_MTL_MEDIA_STEP(gt->i915, STEP_A0, STEP_B0)) {
> > +		/*
> > +		 * Wa_18018781329
> > +		 *
> > +		 * Note that although these registers are MCR on the primary
> > +		 * GT, the media GT's versions are regular singleton registers.
> > +		 */
> > +		wa_write_or(wal, XELPMP_GSC_MOD_CTRL, FORCE_MISS_FTLB);
> > +		wa_write_or(wal, XELPMP_VDBX_MOD_CTRL, FORCE_MISS_FTLB);
> > +		wa_write_or(wal, XELPMP_VEBX_MOD_CTRL, FORCE_MISS_FTLB);
> > +	}
> >  
> >  	debug_dump_steering(gt);
> >  }
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 48c838b4ea62..4295306487c7 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -696,6 +696,10 @@ IS_SUBPLATFORM(const struct drm_i915_private *i915,
> >  	(IS_METEORLAKE(__i915) && \
> >  	 IS_DISPLAY_STEP(__i915, since, until))
> >  
> > +#define IS_MTL_MEDIA_STEP(__i915, since, until) \
> > +	(IS_METEORLAKE(__i915) && \
> > +	 IS_MEDIA_STEP(__i915, since, until))
> > +
> >  /*
> >   * DG2 hardware steppings are a bit unusual.  The hardware design was forked to
> >   * create three variants (G10, G11, and G12) which each have distinct
> > -- 
> > 2.39.1
> > 
> 
> -- 
> Matt Roper
> Graphics Software Engineer
> Linux GPU Platform Enablement
> Intel Corporation



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