[Intel-gfx] [PATCH V3] drm/i915/gt: Add workaround 14016712196

[Andi Shyti]

Hi Tejas,

On Wed, May 31, 2023 at 08:02:14PM +0530, Tejas Upadhyay wrote:
> Wa_14016712196 implementation for mtl
> 
> Bspec: 72197
> 
> V3:
>   - Wrap dummy pipe control stuff in API - Andi
> V2:
>   - Fix  kernel test robot warnings
> 
> Closes: https://lore.kernel.org/oe-kbuild-all/202305121525.3EWdGoBY-lkp@intel.com/
> Signed-off-by: Tejas Upadhyay <tejas.upadhyay at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/gen8_engine_cs.c | 39 ++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/gen8_engine_cs.c b/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
> index e1c76e5bfa82..206947f1fc7c 100644
> --- a/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
> @@ -177,6 +177,30 @@ u32 *gen12_emit_aux_table_inv(struct intel_gt *gt, u32 *cs, const i915_reg_t inv
>  	return cs;
>  }
>  
> +static u32 *mtl_dummy_pipe_control(struct i915_request *rq)
> +{
> +	u32 *cs;
> +
> +	/* Wa_14016712196 */
> +	if (IS_MTL_GRAPHICS_STEP(rq->engine->i915, M, STEP_A0, STEP_B0) ||
> +	    IS_MTL_GRAPHICS_STEP(rq->engine->i915, P, STEP_A0, STEP_B0)) {
> +		int ret;
> +
> +		/* dummy PIPE_CONTROL + depth flush */
> +		cs = intel_ring_begin(rq, 6);
> +		ret = IS_ERR(cs);
> +		if (ret)
> +			return ERR_PTR(ret);
> +		cs = gen12_emit_pipe_control(cs,
> +					     0,
> +					     PIPE_CONTROL_DEPTH_CACHE_FLUSH,
> +					     LRC_PPHWSP_SCRATCH_ADDR);
> +		intel_ring_advance(rq, cs);
> +	}
> +
> +	return cs;

mmmhhh... the value of cs at the end is not used, unless it's an
error. Isn't it better to just have this function as a "static
int" that returns '0' or -errno?

This might also confuse some static analyzers, I guess.

Andi

> +}
> +
>  int gen12_emit_flush_rcs(struct i915_request *rq, u32 mode)
>  {
>  	struct intel_engine_cs *engine = rq->engine;
> @@ -185,6 +209,10 @@ int gen12_emit_flush_rcs(struct i915_request *rq, u32 mode)
>  		u32 flags = 0;
>  		u32 *cs;
>  
> +		cs = mtl_dummy_pipe_control(rq);
> +		if (IS_ERR(cs))
> +			return PTR_ERR(cs);
> +
>  		flags |= PIPE_CONTROL_TILE_CACHE_FLUSH;
>  		flags |= PIPE_CONTROL_FLUSH_L3;
>  		flags |= PIPE_CONTROL_RENDER_TARGET_CACHE_FLUSH;
> @@ -218,6 +246,10 @@ int gen12_emit_flush_rcs(struct i915_request *rq, u32 mode)
>  		u32 flags = 0;
>  		u32 *cs, count;
>  
> +		cs = mtl_dummy_pipe_control(rq);
> +		if (IS_ERR(cs))
> +			return PTR_ERR(cs);
> +
>  		flags |= PIPE_CONTROL_COMMAND_CACHE_INVALIDATE;
>  		flags |= PIPE_CONTROL_TLB_INVALIDATE;
>  		flags |= PIPE_CONTROL_INSTRUCTION_CACHE_INVALIDATE;
> @@ -733,6 +765,13 @@ u32 *gen12_emit_fini_breadcrumb_rcs(struct i915_request *rq, u32 *cs)
>  		     PIPE_CONTROL_DC_FLUSH_ENABLE |
>  		     PIPE_CONTROL_FLUSH_ENABLE);
>  
> +	/* Wa_14016712196 */
> +	if (IS_MTL_GRAPHICS_STEP(i915, M, STEP_A0, STEP_B0) ||
> +	    IS_MTL_GRAPHICS_STEP(i915, P, STEP_A0, STEP_B0))
> +		/* dummy PIPE_CONTROL + depth flush */
> +		cs = gen12_emit_pipe_control(cs, 0,
> +					     PIPE_CONTROL_DEPTH_CACHE_FLUSH, 0);
> +
>  	if (GRAPHICS_VER(i915) == 12 && GRAPHICS_VER_FULL(i915) < IP_VER(12, 50))
>  		/* Wa_1409600907 */
>  		flags |= PIPE_CONTROL_DEPTH_STALL;
> -- 
> 2.25.1