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intel_th: Document debug host mode

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Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
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Alexander Shishkin 2016-09-19 18:06:25 +03:00
parent d4f5f545da
commit ee01aebbe2
1 changed files with 22 additions and 0 deletions
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Documentation/trace/intel_th.txt
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@ -97,3 +97,25 @@ $ echo 0 > /sys/bus/intel_th/devices/0-msc0/active
# and now you can collect the trace from the device node:
$ cat /dev/intel_th0/msc0 > my_stp_trace
Host Debugger Mode
==================
It is possible to configure the Trace Hub and control its trace
capture from a remote debug host, which should be connected via one of
the hardware debugging interfaces, which will then be used to both
control Intel Trace Hub and transfer its trace data to the debug host.
The driver needs to be told that such an arrangement is taking place
so that it does not touch any capture/port configuration and avoids
conflicting with the debug host's configuration accesses. The only
activity that the driver will perform in this mode is collecting
software traces to the Software Trace Hub (an stm class device). The
user is still responsible for setting up adequate master/channel
mappings that the decoder on the receiving end would recognize.
In order to enable the host mode, set the 'host_mode' parameter of the
'intel_th' kernel module to 'y'. None of the virtual output devices
will show up on the intel_th bus. Also, trace configuration and
capture controlling attribute groups of the 'gth' device will not be
exposed. The 'sth' device will operate as usual.