Documentation/trace/stm.rst

1 .. SPDX-License-Identifier: GPL-2.0
9 protocol multiplexing data from multiple trace sources, each one of
10 which is assigned a unique pair of master and channel. While some of
14 master/channel combination from this pool.
17 sources can only be identified by master/channel combination, so in
19 involves multiple trace sources, it needs to be able to map those
20 master/channel pairs to the trace sources that it understands.
23 master 7 channel 15, while arbitrary user applications can use masters
34 associated with it, located in "stp-policy" subsystem directory in
40 	$ ls /config/stp-policy/dummy_stm.my-policy/user
42 	$ cat /config/stp-policy/dummy_stm.my-policy/user/masters
44 	$ cat /config/stp-policy/dummy_stm.my-policy/user/channels
48 masters 48 through 63 and channel allocation pool has channels 0
51 channel from within these ranges.
70 catch-all entry "default" will be used, if it exists. This entry also
79 master/channel range. The new requirement for a policy node to exist
81 and have better control over the un-identified sources.
83 Some STM devices may allow direct mapping of the channel mmio regions
84 to userspace for zero-copy writing. One mappable page (in terms of
85 mmu) will usually contain multiple channels' mmios, so the user will
88 stm device's channel mmio region is 64 bytes and hardware page size is
99 For kernel-based trace sources, there is "stm_source" device
114 used to allocate master and channel numbers. If there's no such policy
115 node, the stm core will use the catch-all entry "default", if one
123 the "stm_console" driver, which basically provides a one-way console
126 To configure the master/channel pair that will be assigned to this
129 consume one channel.
142 * [1] https://software.intel.com/sites/default/files/managed/d3/3c/intel-th-developer-manual.pdf