Re: [Intel-gfx] [RFC PATCH 09/97] drm/i915/guc: Stop using fence/status from CTB descriptor

[Matthew Brost <matthew.brost@intel.com>]

On Thu, May 06, 2021 at 12:13:23PM -0700, Matthew Brost wrote:
> From: Michal Wajdeczko <michal.wajdeczko@intel.com>
> 
> Stop using fence/status from CTB descriptor as future GuC ABI will
> no longer support replies over CTB descriptor.
> 
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> ---
>  .../gt/uc/abi/guc_communication_ctb_abi.h     |  4 +-
>  drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c     | 72 ++-----------------
>  2 files changed, 6 insertions(+), 70 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/uc/abi/guc_communication_ctb_abi.h b/drivers/gpu/drm/i915/gt/uc/abi/guc_communication_ctb_abi.h
> index ebd8c3e0e4bb..d38935f47ecf 100644
> --- a/drivers/gpu/drm/i915/gt/uc/abi/guc_communication_ctb_abi.h
> +++ b/drivers/gpu/drm/i915/gt/uc/abi/guc_communication_ctb_abi.h
> @@ -71,8 +71,8 @@ struct guc_ct_buffer_desc {
>  	u32 head;		/* offset updated by GuC*/
>  	u32 tail;		/* offset updated by owner */
>  	u32 is_in_error;	/* error indicator */
> -	u32 fence;		/* fence updated by GuC */
> -	u32 status;		/* status updated by GuC */
> +	u32 reserved1;
> +	u32 reserved2;
>  	u32 owner;		/* id of the channel owner */
>  	u32 owner_sub_id;	/* owner-defined field for extra tracking */
>  	u32 reserved[5];
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> index 25618649048f..4cc8c0b71699 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
> @@ -90,13 +90,6 @@ static void guc_ct_buffer_desc_init(struct guc_ct_buffer_desc *desc,
>  	desc->owner = CTB_OWNER_HOST;
>  }
>  
> -static void guc_ct_buffer_desc_reset(struct guc_ct_buffer_desc *desc)
> -{
> -	desc->head = 0;
> -	desc->tail = 0;
> -	desc->is_in_error = 0;
> -}
> -
>  static int guc_action_register_ct_buffer(struct intel_guc *guc,
>  					 u32 desc_addr,
>  					 u32 type)
> @@ -315,8 +308,7 @@ static u32 ct_get_next_fence(struct intel_guc_ct *ct)
>  static int ct_write(struct intel_guc_ct *ct,
>  		    const u32 *action,
>  		    u32 len /* in dwords */,
> -		    u32 fence,
> -		    bool want_response)
> +		    u32 fence)
>  {
>  	struct intel_guc_ct_buffer *ctb = &ct->ctbs[CTB_SEND];
>  	struct guc_ct_buffer_desc *desc = ctb->desc;
> @@ -360,8 +352,7 @@ static int ct_write(struct intel_guc_ct *ct,
>  	 * DW2+: action data
>  	 */
>  	header = (len << GUC_CT_MSG_LEN_SHIFT) |
> -		 (GUC_CT_MSG_WRITE_FENCE_TO_DESC) |
> -		 (want_response ? GUC_CT_MSG_SEND_STATUS : 0) |
> +		 GUC_CT_MSG_SEND_STATUS |
>  		 (action[0] << GUC_CT_MSG_ACTION_SHIFT);
>  
>  	CT_DEBUG(ct, "writing %*ph %*ph %*ph\n",
> @@ -390,56 +381,6 @@ static int ct_write(struct intel_guc_ct *ct,
>  	return -EPIPE;
>  }
>  
> -/**
> - * wait_for_ctb_desc_update - Wait for the CT buffer descriptor update.
> - * @desc:	buffer descriptor
> - * @fence:	response fence
> - * @status:	placeholder for status
> - *
> - * Guc will update CT buffer descriptor with new fence and status
> - * after processing the command identified by the fence. Wait for
> - * specified fence and then read from the descriptor status of the
> - * command.
> - *
> - * Return:
> - * *	0 response received (status is valid)
> - * *	-ETIMEDOUT no response within hardcoded timeout
> - * *	-EPROTO no response, CT buffer is in error
> - */
> -static int wait_for_ctb_desc_update(struct guc_ct_buffer_desc *desc,
> -				    u32 fence,
> -				    u32 *status)
> -{
> -	int err;
> -
> -	/*
> -	 * Fast commands should complete in less than 10us, so sample quickly
> -	 * up to that length of time, then switch to a slower sleep-wait loop.
> -	 * No GuC command should ever take longer than 10ms.
> -	 */
> -#define done (READ_ONCE(desc->fence) == fence)
> -	err = wait_for_us(done, 10);
> -	if (err)
> -		err = wait_for(done, 10);
> -#undef done
> -
> -	if (unlikely(err)) {
> -		DRM_ERROR("CT: fence %u failed; reported fence=%u\n",
> -			  fence, desc->fence);
> -
> -		if (WARN_ON(desc->is_in_error)) {
> -			/* Something went wrong with the messaging, try to reset
> -			 * the buffer and hope for the best
> -			 */
> -			guc_ct_buffer_desc_reset(desc);
> -			err = -EPROTO;
> -		}
> -	}
> -
> -	*status = desc->status;
> -	return err;
> -}
> -
>  /**
>   * wait_for_ct_request_update - Wait for CT request state update.
>   * @req:	pointer to pending request
> @@ -483,8 +424,6 @@ static int ct_send(struct intel_guc_ct *ct,
>  		   u32 response_buf_size,
>  		   u32 *status)
>  {
> -	struct intel_guc_ct_buffer *ctb = &ct->ctbs[CTB_SEND];
> -	struct guc_ct_buffer_desc *desc = ctb->desc;
>  	struct ct_request request;
>  	unsigned long flags;
>  	u32 fence;
> @@ -505,16 +444,13 @@ static int ct_send(struct intel_guc_ct *ct,
>  	list_add_tail(&request.link, &ct->requests.pending);
>  	spin_unlock_irqrestore(&ct->requests.lock, flags);
>  
> -	err = ct_write(ct, action, len, fence, !!response_buf);
> +	err = ct_write(ct, action, len, fence);
>  	if (unlikely(err))
>  		goto unlink;
>  
>  	intel_guc_notify(ct_to_guc(ct));
>  
> -	if (response_buf)
> -		err = wait_for_ct_request_update(&request, status);
> -	else
> -		err = wait_for_ctb_desc_update(desc, fence, status);
> +	err = wait_for_ct_request_update(&request, status);
>  	if (unlikely(err))
>  		goto unlink;
>  
> -- 
> 2.28.0
> 
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