linux-kernel - Re: [PATCH RFC 1/3] coresight: tmc: add the handle of the event to the path

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Message-ID: <20250925160440.GD7985@e132581.arm.com>
Date: Thu, 25 Sep 2025 17:04:40 +0100
From: Leo Yan <leo.yan@....com>
To: James Clark <james.clark@...aro.org>
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
	Mike Leach <mike.leach@...aro.org>,
	Jie Gan <jie.gan@....qualcomm.com>,
	Carl Worth <carl@...amperecomputing.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Tingwei Zhang <tingwei.zhang@....qualcomm.com>,
	coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 1/3] coresight: tmc: add the handle of the event to
 the path

On Thu, Sep 25, 2025 at 11:10:51AM +0100, James Clark wrote:

> > > I would suggest in the csdev (coresight_device) structure itself. We
> > > already have some sink specific data in here e.g. perf_sink_id_map.

[...]

> > I think this data is specific to the session we are enabling the
> > device(s) in. e.g., we keep the trace-id in the path.
> > So, I don't mind having this in the path structure.
> > Instead of modifying csdev with additional locking from "etm-perf"
> > it is always cleaner to handle this in the path.
> 
> Yeah, and perf_sink_id_map only "needs" to be in the csdev because it
> controls sharing IDs between multiple paths which can't be accomplished by
> storing it in the path.

This is a bit off-topic: do we really need to maintain an id_map in
every sink device, or could we simply use a global id_map?

I might miss some info; anyway, consolidating trace IDs is a low
priority for me and not critical to this thread. But this might be
benefit for later refactoring.

Thanks,
Leo