Re: [PATCH v4 3/8] drm/xe/lrc: Add helper to capture context timestamp

[Francois Dugast <francois.dugast@intel.com>]

On Wed, May 15, 2024 at 02:42:53PM -0700, Lucas De Marchi wrote:
> From: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> 
> Add a helper to capture CTX_TIMESTAMP from the context image so it can
> be used to calculate the runtime.
> 
> v2: Add kernel-doc to clarify expectation from caller
> 
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

LGTM:
Reviewed-by: Francois Dugast <francois.dugast@intel.com>

> ---
>  drivers/gpu/drm/xe/regs/xe_lrc_layout.h |  1 +
>  drivers/gpu/drm/xe/xe_lrc.c             | 12 ++++++++++++
>  drivers/gpu/drm/xe/xe_lrc.h             | 14 ++++++++++++++
>  drivers/gpu/drm/xe/xe_lrc_types.h       |  3 +++
>  4 files changed, 30 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/regs/xe_lrc_layout.h b/drivers/gpu/drm/xe/regs/xe_lrc_layout.h
> index e6ca8bbda8f4..045dfd09db99 100644
> --- a/drivers/gpu/drm/xe/regs/xe_lrc_layout.h
> +++ b/drivers/gpu/drm/xe/regs/xe_lrc_layout.h
> @@ -11,6 +11,7 @@
>  #define CTX_RING_TAIL			(0x06 + 1)
>  #define CTX_RING_START			(0x08 + 1)
>  #define CTX_RING_CTL			(0x0a + 1)
> +#define CTX_TIMESTAMP			(0x22 + 1)
>  #define CTX_INDIRECT_RING_STATE		(0x26 + 1)
>  #define CTX_PDP0_UDW			(0x30 + 1)
>  #define CTX_PDP0_LDW			(0x32 + 1)
> diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
> index 9b0a4078add3..f679cb9aaea7 100644
> --- a/drivers/gpu/drm/xe/xe_lrc.c
> +++ b/drivers/gpu/drm/xe/xe_lrc.c
> @@ -844,6 +844,7 @@ int xe_lrc_init(struct xe_lrc *lrc, struct xe_hw_engine *hwe,
>  	lrc->tile = gt_to_tile(hwe->gt);
>  	lrc->ring.size = ring_size;
>  	lrc->ring.tail = 0;
> +	lrc->ctx_timestamp = 0;
>  
>  	xe_hw_fence_ctx_init(&lrc->fence_ctx, hwe->gt,
>  			     hwe->fence_irq, hwe->name);
> @@ -898,6 +899,8 @@ int xe_lrc_init(struct xe_lrc *lrc, struct xe_hw_engine *hwe,
>  				     RING_CTL_SIZE(lrc->ring.size) | RING_VALID);
>  	}
>  
> +	xe_lrc_write_ctx_reg(lrc, CTX_TIMESTAMP, 0);
> +
>  	if (xe->info.has_asid && vm)
>  		xe_lrc_write_ctx_reg(lrc, PVC_CTX_ASID, vm->usm.asid);
>  
> @@ -1576,3 +1579,12 @@ void xe_lrc_snapshot_free(struct xe_lrc_snapshot *snapshot)
>  		xe_bo_put(snapshot->lrc_bo);
>  	kfree(snapshot);
>  }
> +
> +u32 xe_lrc_update_timestamp(struct xe_lrc *lrc, u32 *old_ts)
> +{
> +	*old_ts = lrc->ctx_timestamp;
> +
> +	lrc->ctx_timestamp = xe_lrc_read_ctx_reg(lrc, CTX_TIMESTAMP);
> +
> +	return lrc->ctx_timestamp;
> +}
> diff --git a/drivers/gpu/drm/xe/xe_lrc.h b/drivers/gpu/drm/xe/xe_lrc.h
> index e0e841963c23..b9da1031083b 100644
> --- a/drivers/gpu/drm/xe/xe_lrc.h
> +++ b/drivers/gpu/drm/xe/xe_lrc.h
> @@ -66,4 +66,18 @@ void xe_lrc_snapshot_capture_delayed(struct xe_lrc_snapshot *snapshot);
>  void xe_lrc_snapshot_print(struct xe_lrc_snapshot *snapshot, struct drm_printer *p);
>  void xe_lrc_snapshot_free(struct xe_lrc_snapshot *snapshot);
>  
> +/**
> + * xe_lrc_update_timestamp - readout LRC timestamp and update cached value
> + * @lrc: logical ring context for this exec queue
> + * @old_ts: pointer where to save the previous timestamp
> + *
> + * Read the current timestamp for this LRC and update the cached value. The
> + * previous cached value is also returned in @old_ts so the caller can calculate
> + * the delta between 2 updates. Note that this is not intended to be called from
> + * any place, but just by the paths updating the drm client utilization.
> + *
> + * Returns the current LRC timestamp
> + */
> +u32 xe_lrc_update_timestamp(struct xe_lrc *lrc, u32 *old_ts);
> +
>  #endif
> diff --git a/drivers/gpu/drm/xe/xe_lrc_types.h b/drivers/gpu/drm/xe/xe_lrc_types.h
> index cdbf03faef15..0fa055da6b27 100644
> --- a/drivers/gpu/drm/xe/xe_lrc_types.h
> +++ b/drivers/gpu/drm/xe/xe_lrc_types.h
> @@ -45,6 +45,9 @@ struct xe_lrc {
>  
>  	/** @fence_ctx: context for hw fence */
>  	struct xe_hw_fence_ctx fence_ctx;
> +
> +	/** @ctx_timestamp: readout value of CTX_TIMESTAMP on last update */
> +	u32 ctx_timestamp;
>  };
>  
>  struct xe_lrc_snapshot;
> -- 
> 2.43.0
>