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authorLinus Torvalds <torvalds@linux-foundation.org>2018-10-26 19:11:43 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-10-26 19:11:43 +0300
commit18d0eae30e6a4f8644d589243d7ac1d70d29203d (patch)
treefef5a78d54b8763cb17867018356cfe311b31036 /Documentation/trace
parent26873acacbdbb4e4b444f5dd28dcc4853f0e8ba2 (diff)
parent14fdc2c5318ae420e68496975f48dc1dbef52649 (diff)
downloadlinux-18d0eae30e6a4f8644d589243d7ac1d70d29203d.tar.xz
Merge tag 'char-misc-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc
Pull char/misc driver updates from Greg KH: "Here is the big set of char/misc patches for 4.20-rc1. Loads of things here, we have new code in all of these driver subsystems: - fpga - stm - extcon - nvmem - eeprom - hyper-v - gsmi - coresight - thunderbolt - vmw_balloon - goldfish - soundwire along with lots of fixes and minor changes to other small drivers. All of these have been in linux-next for a while with no reported issues" * tag 'char-misc-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (245 commits) Documentation/security-bugs: Clarify treatment of embargoed information lib: Fix ia64 bootloader linkage MAINTAINERS: Clarify UIO vs UIOVEC maintainer docs/uio: fix a grammar nitpick docs: fpga: document programming fpgas using regions fpga: add devm_fpga_region_create fpga: bridge: add devm_fpga_bridge_create fpga: mgr: add devm_fpga_mgr_create hv_balloon: Replace spin_is_locked() with lockdep sgi-xp: Replace spin_is_locked() with lockdep eeprom: New ee1004 driver for DDR4 memory eeprom: at25: remove unneeded 'at25_remove' w1: IAD Register is yet readable trough iad sys file. Fix snprintf (%u for unsigned, count for max size). misc: mic: scif: remove set but not used variables 'src_dma_addr, dst_dma_addr' misc: mic: fix a DMA pool free failure platform: goldfish: pipe: Add a blank line to separate varibles and code platform: goldfish: pipe: Remove redundant casting platform: goldfish: pipe: Call misc_deregister if init fails platform: goldfish: pipe: Move the file-scope goldfish_pipe_dev variable into the driver state platform: goldfish: pipe: Move the file-scope goldfish_pipe_miscdev variable into the driver state ...
Diffstat (limited to 'Documentation/trace')
-rw-r--r--Documentation/trace/stm.rst38
-rw-r--r--Documentation/trace/sys-t.rst62
2 files changed, 91 insertions, 9 deletions
diff --git a/Documentation/trace/stm.rst b/Documentation/trace/stm.rst
index 2c22ddb7fd3e..99f99963e5e7 100644
--- a/Documentation/trace/stm.rst
+++ b/Documentation/trace/stm.rst
@@ -1,3 +1,5 @@
+.. SPDX-License-Identifier: GPL-2.0
+
===================
System Trace Module
===================
@@ -53,12 +55,30 @@ 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.
+trace data into its file descriptor.
+
+In order to find an appropriate policy node for a given trace source,
+several mechanisms can be used. First, a trace source can explicitly
+identify itself by calling an STP_POLICY_ID_SET ioctl on the character
+device's file descriptor, providing their id string, before they write
+any data there. Secondly, if they chose not to perform the explicit
+identification (because you may not want to patch existing software
+to do this), they can just start writing the data, at which point the
+stm core will try to find a policy node with the name matching the
+task's name (e.g., "syslogd") and if one exists, it will be used.
+Thirdly, if the task name can't be found among the policy nodes, the
+catch-all entry "default" will be used, if it exists. This entry also
+needs to be created and configured by the system administrator or
+whatever tools are taking care of the policy configuration. Finally,
+if all the above steps failed, the write() to an stm file descriptor
+will return a error (EINVAL).
+
+Previously, if no policy nodes were found for a trace source, the stm
+class would silently fall back to allocating the first available
+contiguous range of master/channels from the beginning of the device's
+master/channel range. The new requirement for a policy node to exist
+will help programmers and sysadmins identify gaps in configuration
+and have better control over the un-identified sources.
Some STM devices may allow direct mapping of the channel mmio regions
to userspace for zero-copy writing. One mappable page (in terms of
@@ -92,9 +112,9 @@ allocated for the device according to the policy configuration. If
there's a node in the root of the policy directory that matches the
stm_source device's name (for example, "console"), this node will be
used to allocate master and channel numbers. If there's no such policy
-node, the stm core will pick the first contiguous chunk of channels
-within the first available master. Note that the node must exist
-before the stm_source device is connected to its stm device.
+node, the stm core will use the catch-all entry "default", if one
+exists. If neither policy nodes exist, the write() to stm_source_link
+will return an error.
stm_console
===========
diff --git a/Documentation/trace/sys-t.rst b/Documentation/trace/sys-t.rst
new file mode 100644
index 000000000000..3d8eb92735e9
--- /dev/null
+++ b/Documentation/trace/sys-t.rst
@@ -0,0 +1,62 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================
+MIPI SyS-T over STP
+===================
+
+The MIPI SyS-T protocol driver can be used with STM class devices to
+generate standardized trace stream. Aside from being a standard, it
+provides better trace source identification and timestamp correlation.
+
+In order to use the MIPI SyS-T protocol driver with your STM device,
+first, you'll need CONFIG_STM_PROTO_SYS_T.
+
+Now, you can select which protocol driver you want to use when you create
+a policy for your STM device, by specifying it in the policy name:
+
+# mkdir /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/
+
+In other words, the policy name format is extended like this:
+
+ <device_name>:<protocol_name>.<policy_name>
+
+With Intel TH, therefore it can look like "0-sth:p_sys-t.my-policy".
+
+If the protocol name is omitted, the STM class will chose whichever
+protocol driver was loaded first.
+
+You can also double check that everything is working as expected by
+
+# cat /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/protocol
+p_sys-t
+
+Now, with the MIPI SyS-T protocol driver, each policy node in the
+configfs gets a few additional attributes, which determine per-source
+parameters specific to the protocol:
+
+# mkdir /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/default
+# ls /config/stp-policy/dummy_stm.0:p_sys-t.my-policy/default
+channels
+clocksync_interval
+do_len
+masters
+ts_interval
+uuid
+
+The most important one here is the "uuid", which determines the UUID
+that will be used to tag all data coming from this source. It is
+automatically generated when a new node is created, but it is likely
+that you would want to change it.
+
+do_len switches on/off the additional "payload length" field in the
+MIPI SyS-T message header. It is off by default as the STP already
+marks message boundaries.
+
+ts_interval and clocksync_interval determine how much time in milliseconds
+can pass before we need to include a protocol (not transport, aka STP)
+timestamp in a message header or send a CLOCKSYNC packet, respectively.
+
+See Documentation/ABI/testing/configfs-stp-policy-p_sys-t for more
+details.
+
+* [1] https://www.mipi.org/specifications/sys-t