linux-kernel - Re: [PATCH] coresight: Add coresight name support

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Date: Wed, 3 Jan 2024 08:32:56 -0700
From: Rob Herring <robh@...nel.org>
To: Mike Leach <mike.leach@...aro.org>, Mao Jinlong <quic_jinlmao@...cinc.com>
Cc: James Clark <james.clark@....com>, Suzuki K Poulose <suzuki.poulose@....com>, 
	coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	Tingwei Zhang <quic_tingweiz@...cinc.com>, Yuanfang Zhang <quic_yuanfang@...cinc.com>, 
	Tao Zhang <quic_taozha@...cinc.com>, Leo Yan <leo.yan@...aro.org>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: Re: [PATCH] coresight: Add coresight name support

On Tue, Jan 2, 2024 at 5:05 AM Mike Leach <mike.leach@...aro.org> wrote:
>
> As James mentions this is clearly a V2 of a previous patch - please
> mark as such in future.
>
> Adding to what James has already said:-
>
> 1) Mapping between the canonical names used in the drivers and the
> information as to the precise device is as easy as running 'ls' on
> /sys/bus/coresight/devices:-
>
> root@...aro-developer:/home/linaro/cs-mods# ls -al /sys/bus/coresight/devices/
> total 0
> drwxr-xr-x 2 root root 0 Jan  2 11:27 .
> drwxr-xr-x 4 root root 0 Jan  2 11:27 ..
> lrwxrwxrwx 1 root root 0 Jan  2 11:27 cti_cpu0 ->
> ../../../devices/platform/soc@...58000.cti/cti_cpu0
> lrwxrwxrwx 1 root root 0 Jan  2 11:27 cti_cpu1 ->
> ../../../devices/platform/soc@...59000.cti/cti_cpu1
> lrwxrwxrwx 1 root root 0 Jan  2 11:27 cti_cpu2 ->
> ../../../devices/platform/soc@...5a000.cti/cti_cpu2
> lrwxrwxrwx 1 root root 0 Jan  2 11:27 cti_cpu3 ->
> ../../../devices/platform/soc@...5b000.cti/cti_cpu3
> lrwxrwxrwx 1 root root 0 Jan  2 11:27 cti_sys0 ->
> ../../../devices/platform/soc@...10000.cti/cti_sys0
> lrwxrwxrwx 1 root root 0 Jan  2 11:27 cti_sys1 ->
> ../../../devices/platform/soc@...11000.cti/cti_sys1
> lrwxrwxrwx 1 root root 0 Jan  2 11:27 etm0 ->
> ../../../devices/platform/soc@...5c000.etm/etm0
> lrwxrwxrwx 1 root root 0 Jan  2 11:27 etm1 ->
> ../../../devices/platform/soc@...5d000.etm/etm1
> lrwxrwxrwx 1 root root 0 Jan  2 11:27 etm2 ->
> ../../../devices/platform/soc@...5e000.etm/etm2
> lrwxrwxrwx 1 root root 0 Jan  2 11:27 etm3 ->
> ../../../devices/platform/soc@...5f000.etm/etm3
> lrwxrwxrwx 1 root root 0 Jan  2 11:42 funnel0 ->
> ../../../devices/platform/soc@...21000.funnel/funnel0
> lrwxrwxrwx 1 root root 0 Jan  2 11:42 funnel1 ->
> ../../../devices/platform/soc@...41000.funnel/funnel1
> lrwxrwxrwx 1 root root 0 Jan  2 11:42 replicator0 ->
> ../../../devices/platform/soc@...24000.replicator/replicator0
> lrwxrwxrwx 1 root root 0 Jan  2 11:42 tmc_etf0 ->
> ../../../devices/platform/soc@...25000.etf/tmc_etf0
> lrwxrwxrwx 1 root root 0 Jan  2 11:42 tmc_etr0 ->
> ../../../devices/platform/soc@...26000.etr/tmc_etr0
>
>
> 2) The patch set must contain the usage and specification in the .yaml
>  file(s) of the property used.

For the record, I don't like "coresight-name". I don't have another
suggestion because "easy" is not sufficient reasoning for why this is
needed.

> However, there was a standard property called 'name' which is
> deprecated - see
> https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html
> section 2.3.11. I do not believe that adding another 'name' property
> would be accepted by the DT maintainers.

"name" is just the node name for anything in the last 15 years. They
used to be separate, but would still mostly be the same. The only case
I found with them different was old PowerPC Macs.

> 3) the 'device_node' structure has a 'name' field that contains the
> node name in the DT approved "node-name@...t-address" format.

Actually, it is without the unit-address. full_name is with the unit-address.

> This
> contains whatever node names you used in the dt.  Why not use this if
> a change has to be made and find some conditional to activate it.

Don't go accessing "name" or "full_name" directly. I intend to get rid
of "name" and generate it from full_name. So use the accessors and
printk specifiers if you need node names.

Rob