Re: [PATCH] drm/i915/gt: Automate CCS Mode setting during engine resets

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Fri, Apr 26, 2024 at 02:07:23AM +0200, Andi Shyti wrote:
> We missed setting the CCS mode during resume and engine resets.
> Create a workaround to be added in the engine's workaround list.
> This workaround sets the XEHP_CCS_MODE value at every reset.
> 
> The issue can be reproduced by running:
> 
>   $ clpeak --kernel-latency
> 
> Without resetting the CCS mode, we encounter a fence timeout:
> 
>   Fence expiration time out i915-0000:03:00.0:clpeak[2387]:2!
> 
> Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/10895
> Fixes: 6db31251bb26 ("drm/i915/gt: Enable only one CCS for compute workload")
> Reported-by: Gnattu OC <gnattuoc@me.com>
> Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
> Cc: Chris Wilson <chris.p.wilson@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Cc: <stable@vger.kernel.org> # v6.2+

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

> ---
> Hi Gnattu,
> 
> thanks again for reporting this issue and for your prompt
> replies on the issue. Would you give this patch a chance?
> 
> Andi
> 
>  drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.c | 6 +++---
>  drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.h | 2 +-
>  drivers/gpu/drm/i915/gt/intel_workarounds.c | 4 +++-
>  3 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.c b/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.c
> index 044219c5960a..99b71bb7da0a 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.c
> @@ -8,14 +8,14 @@
>  #include "intel_gt_ccs_mode.h"
>  #include "intel_gt_regs.h"
>  
> -void intel_gt_apply_ccs_mode(struct intel_gt *gt)
> +unsigned int intel_gt_apply_ccs_mode(struct intel_gt *gt)
>  {
>  	int cslice;
>  	u32 mode = 0;
>  	int first_ccs = __ffs(CCS_MASK(gt));
>  
>  	if (!IS_DG2(gt->i915))
> -		return;
> +		return 0;
>  
>  	/* Build the value for the fixed CCS load balancing */
>  	for (cslice = 0; cslice < I915_MAX_CCS; cslice++) {
> @@ -35,5 +35,5 @@ void intel_gt_apply_ccs_mode(struct intel_gt *gt)
>  						     XEHP_CCS_MODE_CSLICE_MASK);
>  	}
>  
> -	intel_uncore_write(gt->uncore, XEHP_CCS_MODE, mode);
> +	return mode;
>  }
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.h b/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.h
> index 9e5549caeb26..55547f2ff426 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_ccs_mode.h
> @@ -8,6 +8,6 @@
>  
>  struct intel_gt;
>  
> -void intel_gt_apply_ccs_mode(struct intel_gt *gt);
> +unsigned int intel_gt_apply_ccs_mode(struct intel_gt *gt);
>  
>  #endif /* __INTEL_GT_CCS_MODE_H__ */
> diff --git a/drivers/gpu/drm/i915/gt/intel_workarounds.c b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> index 68b6aa11bcf7..58693923bf6c 100644
> --- a/drivers/gpu/drm/i915/gt/intel_workarounds.c
> +++ b/drivers/gpu/drm/i915/gt/intel_workarounds.c
> @@ -2703,6 +2703,7 @@ add_render_compute_tuning_settings(struct intel_gt *gt,
>  static void ccs_engine_wa_mode(struct intel_engine_cs *engine, struct i915_wa_list *wal)
>  {
>  	struct intel_gt *gt = engine->gt;
> +	u32 mode;
>  
>  	if (!IS_DG2(gt->i915))
>  		return;
> @@ -2719,7 +2720,8 @@ static void ccs_engine_wa_mode(struct intel_engine_cs *engine, struct i915_wa_li
>  	 * After having disabled automatic load balancing we need to
>  	 * assign all slices to a single CCS. We will call it CCS mode 1
>  	 */
> -	intel_gt_apply_ccs_mode(gt);
> +	mode = intel_gt_apply_ccs_mode(gt);
> +	wa_masked_en(wal, XEHP_CCS_MODE, mode);
>  }
>  
>  /*
> -- 
> 2.43.0
>