Re: [Intel-gfx] [PATCH 03/27] drm/i915/guc: Connect the number of guc_ids to debugfs

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

On Thu, Sep 09, 2021 at 03:16:22PM -0700, John Harrison wrote:
> On 8/20/2021 15:44, Matthew Brost wrote:
> > For testing purposes it may make sense to reduce the number of guc_ids
> > available to be allocated. Add debugfs support for setting the number of
> > guc_ids.
> > 
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> It 'may make sense'? Is there an actual IGT/selftest test that uses this and
> needs to in order to not take several hours to run or something? Seems wrong
> to be adding a debugfs interface for something that would only be used for
> testing by internal developers who can quite easy just edit a define in the
> code to simplify their testing.
> 

Had an IGT (gem_exec_parallel) to toggle this to hit certain conditions
that are very hard to hit (guc_id exhaustion) but this was we punted
this problem to the user. Now we likely don't need that test and it is
probably ok to just drop this patch.

Matt

> John.
> 
> 
> > ---
> >   .../gpu/drm/i915/gt/uc/intel_guc_debugfs.c    | 31 +++++++++++++++++++
> >   .../gpu/drm/i915/gt/uc/intel_guc_submission.c |  3 +-
> >   2 files changed, 33 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_debugfs.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_debugfs.c
> > index 887c8c8f35db..b88d343ee432 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_debugfs.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_debugfs.c
> > @@ -71,12 +71,43 @@ static bool intel_eval_slpc_support(void *data)
> >   	return intel_guc_slpc_is_used(guc);
> >   }
> > +static int guc_num_id_get(void *data, u64 *val)
> > +{
> > +	struct intel_guc *guc = data;
> > +
> > +	if (!intel_guc_submission_is_used(guc))
> > +		return -ENODEV;
> > +
> > +	*val = guc->num_guc_ids;
> > +
> > +	return 0;
> > +}
> > +
> > +static int guc_num_id_set(void *data, u64 val)
> > +{
> > +	struct intel_guc *guc = data;
> > +
> > +	if (!intel_guc_submission_is_used(guc))
> > +		return -ENODEV;
> > +
> > +	if (val > guc->max_guc_ids)
> > +		val = guc->max_guc_ids;
> > +	else if (val < 256)
> > +		val = 256;
> > +
> > +	guc->num_guc_ids = val;
> > +
> > +	return 0;
> > +}
> > +DEFINE_SIMPLE_ATTRIBUTE(guc_num_id_fops, guc_num_id_get, guc_num_id_set, "%lld\n");
> > +
> >   void intel_guc_debugfs_register(struct intel_guc *guc, struct dentry *root)
> >   {
> >   	static const struct debugfs_gt_file files[] = {
> >   		{ "guc_info", &guc_info_fops, NULL },
> >   		{ "guc_registered_contexts", &guc_registered_contexts_fops, NULL },
> >   		{ "guc_slpc_info", &guc_slpc_info_fops, &intel_eval_slpc_support},
> > +		{ "guc_num_id", &guc_num_id_fops, NULL },
> >   	};
> >   	if (!intel_guc_is_supported(guc))
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > index 8235e49bb347..68742b612692 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > @@ -2716,7 +2716,8 @@ g2h_context_lookup(struct intel_guc *guc, u32 desc_idx)
> >   	if (unlikely(desc_idx >= guc->max_guc_ids)) {
> >   		drm_err(&guc_to_gt(guc)->i915->drm,
> > -			"Invalid desc_idx %u", desc_idx);
> > +			"Invalid desc_idx %u, max %u",
> > +			desc_idx, guc->max_guc_ids);
> >   		return NULL;
> >   	}
>