linux-kernel - Re: [RFC PATCH] coresight: dynamic-replicator: Fix handling of multiple connections

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Message-ID: <39a2b3fff165a108fa59d72b630b5f14@codeaurora.org>
Date:   Tue, 07 Apr 2020 16:59:05 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     mike.leach@...aro.org, mathieu.poirier@...aro.org,
        leo.yan@...aro.org, alexander.shishkin@...ux.intel.com,
        swboyd@...omium.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [RFC PATCH] coresight: dynamic-replicator: Fix handling of
 multiple connections

Hi Suzuki,

Thanks for looking into this issue.

On 2020-04-07 15:54, Suzuki K Poulose wrote:
> On 04/07/2020 10:46 AM, Sai Prakash Ranjan wrote:
> 
> There seems to be two replicators back to back here. What is connected
> to the other output of both of them ? Are there any TPIUs ? What 
> happens
> if you choose a sink on the other end of "swao_replicator" (ETB ?)
> 

The other outport of swao replicator is connected to EUD which is a
QCOM specific HW which can be used as a sink like USB.
And the other outport of other replicator(replicator_out) is connected 
to
TPIU.

> After boot, what do the idfilter registers read for both the 
> replicators ?
> 

Added some prints in replicator_probe.

  replicator probe ret=-517 devname=6046000.replicator idfilter0=0x0 
idfilter1=0x0
  replicator probe ret=0 devname=6b06000.replicator idfilter0=0xff 
idfilter1=0xff
  replicator probe ret=0 devname=6046000.replicator idfilter0=0xff 
idfilter1=0xff

> 
> I believe we need to properly assign the TRACE_IDs for tracing 
> sessions,
> (rather than static ids) in a way such that we could filter them and 
> use
> the multiple sinks in parallel for separate trace sessions and this is
> not simple (involves kernel driver changes and the perf tool to be able
> to decode the trace id changes too).
> 
> 
> So for the moment, we need to :
> 
> 1) Disallow turning the replicator ON, when it is already turned ON
> 2) Do what your patch does. i.e, disable the other end while one end
>    is turned on.
> 
> Thoughts ?
> 

Sounds good to me, Mike would have some comments.

Thanks,
Sai

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