[PATCH V3] coresight: Make sysFS functional on topologies with per core sink

[Linu Cherian]

Hi Mathieu,

> > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
> > index 1a3169e69bb1..25041d2654e3 100644
> > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> > @@ -223,7 +223,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
> >  		id = (u32)event->attr.config2;
> >  		sink = coresight_get_sink_by_id(id);
> >  	} else {
> > -		sink = coresight_get_enabled_sink(true);
> > +		sink = coresight_get_enabled_sink(NULL, true);
> 
> It is time for this subsystem to move out of the prehistoric age.  Please remove
> the call to coresight_get_enabled_sink() entirely.  In the change log you can
> write that selecting a sink from sysfs is deprecated when using the perf
> interface.  I will personally refactor the code if someone complains that it
> broke their user space.

Okay fine.

> 
> >  	}
> >  
> >  	mask = &event_data->mask;
> > diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> > index f2dc625ea585..010ed26db340 100644
> > --- a/drivers/hwtracing/coresight/coresight-priv.h
> > +++ b/drivers/hwtracing/coresight/coresight-priv.h
> > @@ -148,10 +148,13 @@ static inline void coresight_write_reg_pair(void __iomem *addr, u64 val,
> >  void coresight_disable_path(struct list_head *path);
> >  int coresight_enable_path(struct list_head *path, u32 mode, void *sink_data);
> >  struct coresight_device *coresight_get_sink(struct list_head *path);
> > -struct coresight_device *coresight_get_enabled_sink(bool reset);
> > +struct coresight_device *
> > +coresight_get_enabled_sink(struct coresight_device *source, bool reset);
> >  struct coresight_device *coresight_get_sink_by_id(u32 id);
> >  struct coresight_device *
> >  coresight_find_default_sink(struct coresight_device *csdev);
> > +struct coresight_device *
> > +coresight_find_enabled_sink(struct coresight_device *csdev);
> >  struct list_head *coresight_build_path(struct coresight_device *csdev,
> >  				       struct coresight_device *sink);
> >  void coresight_release_path(struct list_head *path);
> > diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
> > index e9c90f2de34a..ae69169c58d3 100644
> > --- a/drivers/hwtracing/coresight/coresight.c
> > +++ b/drivers/hwtracing/coresight/coresight.c
> > @@ -566,6 +566,10 @@ static int coresight_enabled_sink(struct device *dev, const void *data)
> >  
> >  /**
> >   * coresight_get_enabled_sink - returns the first enabled sink found on the bus
> > + * When a source reference is given, enabled sink is found using connection based
> > + * search.
> > + *
> > + * @source: Coresight source device reference
> >   * @deactivate:	Whether the 'enable_sink' flag should be reset
> >   *
> >   * When operated from perf the deactivate parameter should be set to 'true'.
> > @@ -576,10 +580,21 @@ static int coresight_enabled_sink(struct device *dev, const void *data)
> >   * parameter should be set to 'false', hence mandating users to explicitly
> >   * clear the flag.
> >   */
> > -struct coresight_device *coresight_get_enabled_sink(bool deactivate)
> > +struct coresight_device *
> > +coresight_get_enabled_sink(struct coresight_device *source, bool deactivate)
> 
> This code was written during a time when all sources were able to reach a sink,
> something that is no longer the case.  Starting from a source is the right way
> to go.
> 
> >  {
> >  	struct device *dev = NULL;
> > +	struct coresight_device *sink;
> > +
> > +	if (!source)
> > +		goto bus_search;
> 
> Return NULL if a source was not given.

Agree, since we are removing invocations from perf.

> 
> > +	sink = coresight_find_enabled_sink(source);
> > +	if (sink && deactivate)
> > +		sink->activated = false;
> > +
> > +	return sink;
> 
> You get credits for trying to re-use code but in this case I would like to avoid
> modifying coresight_find_sink() to keep it as simple as possible.  I suggest to
> copy the for() loop in coresight_find_sink() and stop the search when the first
> activated sink is found.  It will introduce a little bit of code duplication but
> I think we will gain a lot in maintainability.

Fine. 

> 
> >  
> > +bus_search:
> >  	dev = bus_find_device(&coresight_bustype, NULL, &deactivate,
> >  			      coresight_enabled_sink);
>
> Get rid of this.  You can also get rid of the 'deactivate' parameter since it
> won't be used anymore. 

Agree, since perf doesnt require this anymore.

> 
> Let me know if you have questions.

Sure. Thanks.

-- 
Linu cherian