linux-kernel - [PATCH v2] coresight: documentation: update sysfs section

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Message-Id: <20180514121959.a9a3d2fb3d3d270849ffbc39@arm.com>
Date:   Mon, 14 May 2018 12:19:59 -0500
From:   Kim Phillips <kim.phillips@....com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     Jonathan Corbet <corbet@....net>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] coresight: documentation: update sysfs section

- 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: Jonathan Corbet <corbet@....net>
Signed-off-by: Kim Phillips <kim.phillips@....com>
---
v2: address Mathieu's comment about clarifying the sinks on the Juno
vs. TC2 platforms.

 Documentation/trace/coresight.txt | 41 +++++++++++++++++++------------
 1 file changed, 25 insertions(+), 16 deletions(-)

diff --git a/Documentation/trace/coresight.txt
b/Documentation/trace/coresight.txt index 6f0120c3a4f1..134994e9fa6d
100644
--- a/Documentation/trace/coresight.txt
+++ b/Documentation/trace/coresight.txt
@@ -144,10 +144,22 @@ 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: 
 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