[Intel-gfx] [PATCH 3/7] drm/i915/guc: Add GuC <-> kernel time stamp translation information

[Teres Alexis, Alan Previn]

I have a question on below code. Everything else looked good.
Will r-b as soon as we can close on below question
...alan


On Wed, 2022-07-27 at 19:20 -0700, John.C.Harrison at Intel.com wrote:
> From: John Harrison <John.C.Harrison at Intel.com>
> 
> It is useful to be able to match GuC events to kernel events when
> looking at the GuC log. That requires being able to convert GuC
> timestamps to kernel time. So, when dumping error captures and/or GuC
> logs, include a stamp in both time zones plus the clock frequency.
> 
> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
> --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> @@ -1675,6 +1678,13 @@ gt_record_uc(struct intel_gt_coredump *gt,
>  	 */
>  	error_uc->guc_fw.path = kstrdup(uc->guc.fw.path, ALLOW_FAIL);
>  	error_uc->huc_fw.path = kstrdup(uc->huc.fw.path, ALLOW_FAIL);
> +
> +	/*
> +	 * Save the GuC log and include a timestamp reference for converting the
> +	 * log times to system times (in conjunction with the error->boottime and
> +	 * gt->clock_frequency fields saved elsewhere).
> +	 */
> +	error_uc->timestamp = intel_uncore_read(gt->_gt->uncore, GUCPMTIMESTAMP);

Alan:this register is in the GUC-SHIM domain and so unless i am mistaken u might need to ensure we hold a wakeref so
that are getting a live value of the real timestamp register that this register is mirror-ing and not a stale snapshot.
Or was this already done farther up the stack? Or are we doing the opposite - in which case we should ensure we drop al
 wakeref prior to this point. (which i am not sure is a reliable method since we wouldnt know what GuC ref was at). 
>  	error_uc->guc_log = create_vma_coredump(gt->_gt, uc->guc.log.vma,
>  						"GuC log buffer", compress);
>