Re: [PATCH] drm/xe/guc: Return CTB response length

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

On Thu, Jan 11, 2024 at 06:07:12PM +0100, Michal Wajdeczko wrote:
> 
> 
> On 11.01.2024 17:40, Matthew Brost wrote:
> > On Thu, Jan 11, 2024 at 04:27:24PM +0100, Michal Wajdeczko wrote:
> >> Not all CTB responses from the GuC are fixed size and we need to
> >> pass response length to the caller, if there was a response_buffer.
> >> Easiest solution is to return it as positive value from all
> >> xe_guc_ct_send_recv() functions.  The CTB response length is always
> >> between 1 and 254 (ie. GUC_HXG_MSG_MIN_LEN and GUC_CTB_MAX_DWORDS
> >> - GUC_HXG_MSG_MIN_LEN).
> >>
> >> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
> >> Cc: Matthew Brost <matthew.brost@intel.com>
> > 
> > I has purposed a different usage of the return value [1].
> > 
> > Perhaps we just have response len as a pass by ref argument?
> 
> no need for additional argument, we can still return data0 if there was
> no response_buffer provided, and I also have patch for this, but didn't
> send right now as it conflicts with our already in-flight HXG changes.
> 
> Michal
> 

Ok this LGTM. We will need some kernel doc for GuC CT soon. Let me open
a Jira for that so we don't lose track of this.

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

> > 
> > Matt
> > 
> > [1] https://patchwork.freedesktop.org/patch/541762/?series=119096&rev=1
> > 
> >> ---
> >>  drivers/gpu/drm/xe/xe_guc_ct.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
> >> index c29f095aa1b9..d490a4d42c01 100644
> >> --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> >> +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> >> @@ -780,7 +780,7 @@ static int guc_ct_send_recv(struct xe_guc_ct *ct, const u32 *action, u32 len,
> >>  		ret = -EIO;
> >>  	}
> >>  
> >> -	return ret > 0 ? 0 : ret;
> >> +	return ret > 0 ? response_buffer ? g2h_fence.response_len : 0 : ret;
> >>  }
> >>  
> >>  int xe_guc_ct_send_recv(struct xe_guc_ct *ct, const u32 *action, u32 len,
> >>
> >> base-commit: 79184e72263e91528195db01783148435c7e4fad
> >> -- 
> >> 2.25.1
> >>