diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/configfs-stp-policy | 48 | ||||
| -rw-r--r-- | Documentation/ABI/testing/sysfs-class-stm | 14 | ||||
| -rw-r--r-- | Documentation/ABI/testing/sysfs-class-stm_source | 11 | ||||
| -rw-r--r-- | Documentation/ioctl/ioctl-number.txt | 3 | ||||
| -rw-r--r-- | Documentation/trace/stm.txt | 80 |
5 files changed, 156 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/configfs-stp-policy b/Documentation/ABI/testing/configfs-stp-policy new file mode 100644 index 000000000000..421ce6825c66 --- /dev/null +++ b/Documentation/ABI/testing/configfs-stp-policy @@ -0,0 +1,48 @@ +What: /config/stp-policy +Date: June 2015 +KernelVersion: 4.3 +Description: + This group contains policies mandating Master/Channel allocation + for software sources wishing to send trace data over an STM + device. + +What: /config/stp-policy/<device>.<policy> +Date: June 2015 +KernelVersion: 4.3 +Description: + This group is the root of a policy; its name is a concatenation + of an stm device name to which this policy applies and an + arbitrary string. If <device> part doesn't match an existing + stm device, mkdir will fail with ENODEV; if that device already + has a policy assigned to it, mkdir will fail with EBUSY. + +What: /config/stp-policy/<device>.<policy>/device +Date: June 2015 +KernelVersion: 4.3 +Description: + STM device to which this policy applies, read only. Same as the + <device> component of its parent directory. + +What: /config/stp-policy/<device>.<policy>/<node> +Date: June 2015 +KernelVersion: 4.3 +Description: + Policy node is a string identifier that software clients will + use to request a master/channel to be allocated and assigned to + them. + +What: /config/stp-policy/<device>.<policy>/<node>/masters +Date: June 2015 +KernelVersion: 4.3 +Description: + Range of masters from which to allocate for users of this node. + Write two numbers: the first master and the last master number. + +What: /config/stp-policy/<device>.<policy>/<node>/channels +Date: June 2015 +KernelVersion: 4.3 +Description: + Range of channels from which to allocate for users of this node. + Write two numbers: the first channel and the last channel + number. + diff --git a/Documentation/ABI/testing/sysfs-class-stm b/Documentation/ABI/testing/sysfs-class-stm new file mode 100644 index 000000000000..c9aa4f3fc9a7 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-stm @@ -0,0 +1,14 @@ +What: /sys/class/stm/<stm>/masters +Date: June 2015 +KernelVersion: 4.3 +Contact: Alexander Shishkin <alexander.shishkin@linux.intel.com> +Description: + Shows first and last available to software master numbers on + this STM device. + +What: /sys/class/stm/<stm>/channels +Date: June 2015 +KernelVersion: 4.3 +Contact: Alexander Shishkin <alexander.shishkin@linux.intel.com> +Description: + Shows the number of channels per master on this STM device. diff --git a/Documentation/ABI/testing/sysfs-class-stm_source b/Documentation/ABI/testing/sysfs-class-stm_source new file mode 100644 index 000000000000..57b8dd39bbf7 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-stm_source @@ -0,0 +1,11 @@ +What: /sys/class/stm_source/<stm_source>/stm_source_link +Date: June 2015 +KernelVersion: 4.3 +Contact: Alexander Shishkin <alexander.shishkin@linux.intel.com> +Description: + stm_source device linkage to stm device, where its tracing data + is directed. Reads return an existing connection or "<none>" if + this stm_source is not connected to any stm device yet. + Write an existing (registered) stm device's name here to + connect that device. If a device is already connected to this + stm_source, it will first be disconnected. diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt index df1b25eb8382..3785b7e131f8 100644 --- a/Documentation/ioctl/ioctl-number.txt +++ b/Documentation/ioctl/ioctl-number.txt @@ -81,6 +81,9 @@ Code Seq#(hex) Include File Comments 0x22 all scsi/sg.h '#' 00-3F IEEE 1394 Subsystem Block for the entire subsystem '$' 00-0F linux/perf_counter.h, linux/perf_event.h +'%' 00-0F include/uapi/linux/stm.h + System Trace Module subsystem + <mailto:alexander.shishkin@linux.intel.com> '&' 00-07 drivers/firewire/nosy-user.h '1' 00-1F <linux/timepps.h> PPS kit from Ulrich Windl <ftp://ftp.de.kernel.org/pub/linux/daemons/ntp/PPS/> diff --git a/Documentation/trace/stm.txt b/Documentation/trace/stm.txt new file mode 100644 index 000000000000..ea035f9dbfd7 --- /dev/null +++ b/Documentation/trace/stm.txt @@ -0,0 +1,80 @@ +System Trace Module +=================== + +System Trace Module (STM) is a device described in MIPI STP specs as +STP trace stream generator. STP (System Trace Protocol) is a trace +protocol multiplexing data from multiple trace sources, each one of +which is assigned a unique pair of master and channel. While some of +these masters and channels are statically allocated to certain +hardware trace sources, others are available to software. Software +trace sources are usually free to pick for themselves any +master/channel combination from this pool. + +On the receiving end of this STP stream (the decoder side), trace +sources can only be identified by master/channel combination, so in +order for the decoder to be able to make sense of the trace that +involves multiple trace sources, it needs to be able to map those +master/channel pairs to the trace sources that it understands. + +For instance, it is helpful to know that syslog messages come on +master 7 channel 15, while arbitrary user applications can use masters +48 to 63 and channels 0 to 127. + +To solve this mapping problem, stm class provides a policy management +mechanism via configfs, that allows defining rules that map string +identifiers to ranges of masters and channels. If these rules (policy) +are consistent with what decoder expects, it will be able to properly +process the trace data. + +This policy is a tree structure containing rules (policy_node) that +have a name (string identifier) and a range of masters and channels +associated with it, located in "stp-policy" subsystem directory in +configfs. The topmost directory's name (the policy) is formatted as +the STM device name to which this policy applies and and arbitrary +string identifier separated by a stop. From the examle above, a rule +may look like this: + +$ ls /config/stp-policy/dummy_stm.my-policy/user +channels masters +$ cat /config/stp-policy/dummy_stm.my-policy/user/masters +48 63 +$ cat /config/stp-policy/dummy_stm.my-policy/user/channels +0 127 + +which means that the master allocation pool for this rule consists of +masters 48 through 63 and channel allocation pool has channels 0 +through 127 in it. Now, any producer (trace source) identifying itself +with "user" identification string will be allocated a master and +channel from within these ranges. + +These rules can be nested, for example, one can define a rule "dummy" +under "user" directory from the example above and this new rule will +be used for trace sources with the id string of "user/dummy". + +Trace sources have to open the stm class device's node and write their +trace data into its file descriptor. In order to identify themselves +to the policy, they need to do a STP_POLICY_ID_SET ioctl on this file +descriptor providing their id string. Otherwise, they will be +automatically allocated a master/channel pair upon first write to this +file descriptor according to the "default" rule of the policy, if such +exists. + +Some STM devices may allow direct mapping of the channel mmio regions +to userspace for zero-copy writing. One mappable page (in terms of +mmu) will usually contain multiple channels' mmios, so the user will +need to allocate that many channels to themselves (via the +aforementioned ioctl() call) to be able to do this. That is, if your +stm device's channel mmio region is 64 bytes and hardware page size is +4096 bytes, after a successful STP_POLICY_ID_SET ioctl() call with +width==64, you should be able to mmap() one page on this file +descriptor and obtain direct access to an mmio region for 64 channels. + +For kernel-based trace sources, there is "stm_source" device +class. Devices of this class can be connected and disconnected to/from +stm devices at runtime via a sysfs attribute. + +Examples of STM devices are Intel(R) Trace Hub [1] and Coresight STM +[2]. + +[1] https://software.intel.com/sites/default/files/managed/d3/3c/intel-th-developer-manual.pdf +[2] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0444b/index.html |