linux-kernel - Re: [PATCH v3] coresight: documentation: update sysfs section

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Date:   Tue, 15 May 2018 10:00:51 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Kim Phillips <kim.phillips@....com>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Jonathan Corbet <corbet@....net>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] coresight: documentation: update sysfs section

On 14 May 2018 at 13:18, Kim Phillips <kim.phillips@....com> wrote:
> - Align and show updated ls devices output from the TC2, based on
>   current driver
>
> - Provide an example from an ETMv4 based system (Juno)
>
> - Reflect changes to the way the RAM write pointer is accessed since
>   it got changed in commit 7d83d17795ef ("coresight: tmc: adding sysFS
>   management entries").
>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Cc: Randy Dunlap <rdunlap@...radead.org>
> Cc: Jonathan Corbet <corbet@....net>
> Signed-off-by: Kim Phillips <kim.phillips@....com>

I'm good with this version - Jonathan, should I take this through my
tree of you'll take care of it?

In case of the former:
Acked-by: Mathieu Poirier <mathieu.poirier@...aro.org>

> ---
> v3: address Randy Dunlap's showns->shown,  corrected - and + line merging
> v2: address Mathieu's comment about clarifying the sinks on the Juno
>     vs. TC2 platforms.
>
>  Documentation/trace/coresight.txt | 43 +++++++++++++++++++------------
>  1 file changed, 26 insertions(+), 17 deletions(-)
>
> diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt
> index 6f0120c3a4f1..15d2a0f1e1b8 100644
> --- a/Documentation/trace/coresight.txt
> +++ b/Documentation/trace/coresight.txt
> @@ -141,13 +141,25 @@ register the device with the core framework.  The unregister function takes
>  a reference to a "struct coresight_device", obtained at registration time.
>
>  If everything goes well during the registration process the new devices will
> -show up under /sys/bus/coresight/devices, as showns here for a TC2 platform:
> +show up under /sys/bus/coresight/devices, as shown here for a TC2 platform:
>
>  root:~# ls /sys/bus/coresight/devices/
> -replicator  20030000.tpiu    2201c000.ptm  2203c000.etm  2203e000.etm
> -20010000.etb         20040000.funnel  2201d000.ptm  2203d000.etm
> +20010000.etb   20040000.funnel 2201d000.ptm  2203d000.etm  replicator
> +20030000.tpiu  2201c000.ptm    2203c000.etm  2203e000.etm
>  root:~#
>
> +and here for a Juno platform:
> +
> +root@...o:~# ls /sys/bus/coresight/devices/
> +20010000.etf    20120000.replicator  22040000.etm     230c0000.funnel
> +20030000.tpiu   20130000.funnel      220c0000.funnel  23140000.etm
> +20040000.funnel  20140000.etf        22140000.etm     23240000.etm
> +20070000.etr    20150000.funnel      23040000.etm     23340000.etm
> +root@...o:~#
> +
> +Note that on Juno users can select the ETF, ETR and TPIU as a sink target while
> +on TC2, the ETB and TPIU can be selected.
> +
>  The functions take a "struct coresight_device", which looks like this:
>
>  struct coresight_desc {
> @@ -193,16 +205,16 @@ the information carried in "THIS_MODULE".
>  How to use the tracer modules
>  -----------------------------
>
> -Before trace collection can start, a coresight sink needs to be identify.
> +Before trace collection can start, a coresight sink needs to be identified.
>  There is no limit on the amount of sinks (nor sources) that can be enabled at
>  any given moment.  As a generic operation, all device pertaining to the sink
>  class will have an "active" entry in sysfs:
>
>  root:/sys/bus/coresight/devices# ls
> -replicator  20030000.tpiu    2201c000.ptm  2203c000.etm  2203e000.etm
> -20010000.etb         20040000.funnel  2201d000.ptm  2203d000.etm
> +20010000.etb   20040000.funnel 2201d000.ptm  2203d000.etm  replicator
> +20030000.tpiu  2201c000.ptm    2203c000.etm  2203e000.etm
>  root:/sys/bus/coresight/devices# ls 20010000.etb
> -enable_sink  status  trigger_cntr
> +enable_sink  mgmt  power  subsystem  trigger_cntr  uevent
>  root:/sys/bus/coresight/devices# echo 1 > 20010000.etb/enable_sink
>  root:/sys/bus/coresight/devices# cat 20010000.etb/enable_sink
>  1
> @@ -216,16 +228,13 @@ trigger a trace capture:
>  root:/sys/bus/coresight/devices# echo 1 > 2201c000.ptm/enable_source
>  root:/sys/bus/coresight/devices# cat 2201c000.ptm/enable_source
>  1
> -root:/sys/bus/coresight/devices# cat 20010000.etb/status
> -Depth:          0x2000
> -Status:         0x1
> -RAM read ptr:   0x0
> -RAM wrt ptr:    0x19d3   <----- The write pointer is moving
> -Trigger cnt:    0x0
> -Control:        0x1
> -Flush status:   0x0
> -Flush ctrl:     0x2001
> -root:/sys/bus/coresight/devices#
> +
> +Observe the write pointer moving:
> +
> +root:/sys/bus/coresight/devices# cat 20010000.etb/mgmt/rwp
> +0x1a8
> +root:/sys/bus/coresight/devices# cat 20010000.etb/mgmt/rwp
> +0x19a6
>
>  Trace collection is stopped the same way:
>
> --
> 2.17.0
>