Re: [Intel-gfx] [PATCH v5] drm/i915: Added Wa_18022495364

From: Matt Roper <matthew.d.roper@intel.com>
To: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Cc: intel-gfx@lists.freedesktop.org,
	Lucas De Marchi <lucas.demarchi@intel.com>
Subject: Re: [Intel-gfx] [PATCH v5] drm/i915: Added Wa_18022495364
Date: Thu, 14 Sep 2023 09:49:26 -0700	[thread overview]
Message-ID: <20230914164926.GT2706891@mdroper-desk1.amr.corp.intel.com> (raw)
In-Reply-To: <20230914134724.657957-1-dnyaneshwar.bhadane@intel.com>

On Thu, Sep 14, 2023 at 07:17:24PM +0530, Dnyaneshwar Bhadane wrote:
> Set the instruction and state cache invalidate bit using INDIRECT_CTX on
> every gpu context switch. 
> The goal of this workaround is to actually perform an explicit
> invalidation of that cache (by re-writing the register) during every GPU
> context switch, which is accomplished via a "workaround batchbuffer"
> that's attached to the context via INDIRECT_CTX. (Matt)
> BSpec: 11354
> 
> v2:
> - Removed extra parentheses from the condition (Lucas)
> - Fixed spacing and new line (Lucas)
> 
> v3:
> - Fixed commit message.
> 
> v4:
> - Only GEN12 changes are kept  (Matt Ropper)
> - Fixed the commit message for r-b (Matt Ropper)
> - Renamed the register bit in define
> 
> v5:
> - Moved out the  from golden context init (Matt Roper)
> - Use INDIRECT_CTX to set bit on each GPU context switch (Matt Roper)
> 
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Signed-off-by: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
> 
> ---
>  drivers/gpu/drm/i915/gt/intel_gt_regs.h |  2 ++
>  drivers/gpu/drm/i915/gt/intel_lrc.c     | 15 +++++++++++++++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_regs.h b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> index 0e4c638fcbbf..38f02ef8ed01 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_regs.h
> @@ -164,6 +164,8 @@
>  #define GEN9_CSFE_CHICKEN1_RCS			_MMIO(0x20d4)
>  #define   GEN9_PREEMPT_GPGPU_SYNC_SWITCH_DISABLE	(1 << 2)
>  #define   GEN11_ENABLE_32_PLANE_MODE		(1 << 7)
> +#define GEN12_CS_DEBUG_MODE2			_MMIO(0x20d8)
> +#define   INSTRUCTION_STATE_CACHE_INVALIDATE	REG_BIT(6)
>  
>  #define GEN7_FF_SLICE_CS_CHICKEN1		_MMIO(0x20e0)
>  #define   GEN9_FFSC_PERCTX_PREEMPT_CTRL		(1 << 14)
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 967fe4d77a87..fe98039499c5 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -1332,6 +1332,15 @@ dg2_emit_draw_watermark_setting(u32 *cs)
>  	return cs;
>  }
>  
> +static u32 *
> +gen12_set_instruction_state_cache_invalid(u32 *cs)

Minor nitpick:  I'd name this "gen12_invalidate_state_cache."  The
general terminology with caches is that we "invalidate" them rather than
"set invalid," and that also matches the terminology used by the
register bit itself.

> +{
> +	*cs++ = MI_LOAD_REGISTER_IMM(1);
> +	*cs++ = i915_mmio_reg_offset(GEN12_CS_DEBUG_MODE2);
> +	*cs++ = _MASKED_BIT_ENABLE(INSTRUCTION_STATE_CACHE_INVALIDATE);
> +	return cs;
> +}
> +
>  static u32 *
>  gen12_emit_indirect_ctx_rcs(const struct intel_context *ce, u32 *cs)
>  {
> @@ -1345,6 +1354,12 @@ gen12_emit_indirect_ctx_rcs(const struct intel_context *ce, u32 *cs)
>  
>  	cs = gen12_emit_aux_table_inv(ce->engine, cs);
>  
> +	/* Wa_18022495364 */
> +	if (IS_ALDERLAKE_P(ce->engine->i915) || IS_ALDERLAKE_P_N(ce->engine->i915) ||

ADL-N is defined as a subplatform of ADL-P in the driver, so ADL-N
platforms will automatically be matched by the IS_ALDERLAKE_P; you don't
need the IS_ALDERLAKE_P_N condition here (that's only for the rare
places where we want to match ADL-N specifically _without_ matching
other ADL-P platforms as well).

> +	    IS_ALDERLAKE_S(ce->engine->i915) || IS_TIGERLAKE(ce->engine->i915) ||
> +		IS_ROCKETLAKE(ce->engine->i915) || IS_DG1(ce->engine->i915))

Since this workaround winds up applying to every single gen12lp platform, it's
probably simpler to just write the condition as

    if (IS_GFX_GT_IP_RANGE(cs->engine->i915), IP_VER(12, 0), IP_VER(12, 10))

Matt

> +		cs = gen12_set_instruction_state_cache_invalid(cs);
> +
>  	/* Wa_16014892111 */
>  	if (IS_GFX_GT_IP_STEP(ce->engine->gt, IP_VER(12, 70), STEP_A0, STEP_B0) ||
>  	    IS_GFX_GT_IP_STEP(ce->engine->gt, IP_VER(12, 71), STEP_A0, STEP_B0) ||
> -- 
> 2.34.1
> 

-- 
Matt Roper
Graphics Software Engineer
Linux GPU Platform Enablement
Intel Corporation