[PATCH v3] coresight: documentation: update sysfs section
From: Kim Phillips <hidden>
Date: 2018-05-14 19:18:03
Also in:
linux-doc, lkml
Subsystem:
documentation, the rest, tracing · Maintainers:
Jonathan Corbet, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
- 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@linaro.org>
Cc: Randy Dunlap <redacted>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Kim Phillips <redacted>
---
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 at juno:~# 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 at juno:~# + +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