Re: [Intel-gfx] [PATCH v2] drm/i915/dg2: Add performance workaround 18019455067

[Matt Roper <matthew.d.roper@intel.com>]

On Mon, Jun 27, 2022 at 03:59:28PM +0300, Lionel Landwerlin wrote:
> The recommended number of stackIDs for Ray Tracing subsystem is 512
> rather than 2048 (default HW programming).
> 
> v2: Move the programming to dg2_ctx_gt_tuning_init() (Lucas)

I'm not sure this is actually the correct move.  As far as I can see on
bspec 46261, RT_CTRL isn't part of the engine's context, so we need to
make sure it gets added to engine->wa_list instead of
engine->ctx_wa_list, otherwise it won't be properly re-applied after
engine resets and such.  Most of our other tuning values are part of the
context image, so this one is a bit unusual.

To get it onto the engine->wa_list, the workaround needs to either be
defined via rcs_engine_wa_init() or general_render_compute_wa_init().
The latter is the new, preferred location for registers that are part of
the render/compute reset domain, but that don't live in the RCS engine's
0x2xxx MMIO range (since all RCS and CCS engines get reset together, the
items in general_render_compute_wa_init() will make sure it's dealt with
as part of the handling for the first RCS/CCS engine, so that we won't
miss out on applying it if the platform doesn't have an RCS).

At the moment we don't have too many "tuning" values that we need to set
that aren't part of an engine's context, so we don't yet have a
dedicated "tuning" function for engine-style workarounds like we do with
ctx-style workarounds.


Matt

> 
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_gt_regs.h     | 4 ++++
>  drivers/gpu/drm/i915/gt/intel_workarounds.c | 5 +++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> index 07ef111947b8c..12fc87b957425 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> @@ -1112,6 +1112,10 @@
>  #define   GEN12_PUSH_CONST_DEREF_HOLD_DIS	REG_BIT(8)
>  
>  #define RT_CTRL					_MMIO(0xe530)
> +#define   RT_CTRL_NUMBER_OF_STACKIDS_MASK	REG_GENMASK(6, 5)
> +#define   NUMBER_OF_STACKIDS_512		2
> +#define   NUMBER_OF_STACKIDS_1024		1
> +#define   NUMBER_OF_STACKIDS_2048		0
>  #define   DIS_NULL_QUERY			REG_BIT(10)
>  
>  #define EU_PERF_CNTL1				_MMIO(0xe558)
> diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> index 3213c593a55f4..4d80716b957d4 100644
> --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> @@ -575,6 +575,11 @@ static void dg2_ctx_gt_tuning_init(struct intel_engine_cs *engine,
>  	       FF_MODE2_TDS_TIMER_MASK,
>  	       FF_MODE2_TDS_TIMER_128,
>  	       0, false);
> +	wa_write_clr_set(wal,
> +			 RT_CTRL,
> +			 RT_CTRL_NUMBER_OF_STACKIDS_MASK,
> +			 REG_FIELD_PREP(RT_CTRL_NUMBER_OF_STACKIDS_MASK,
> +					NUMBER_OF_STACKIDS_512));
>  }
>  
>  /*
> -- 
> 2.34.1
> 

-- 
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation