On Sat, Apr 17, 2021 at 06:17:10PM +0800, Yicong Yang wrote:
Document the introduction and usage of HiSilicon PTT device driver.
Signed-off-by: Yicong Yang yangyicong@hisilicon.com
Documentation/trace/hisi-ptt.rst | 326 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 326 insertions(+) create mode 100644 Documentation/trace/hisi-ptt.rst
diff --git a/Documentation/trace/hisi-ptt.rst b/Documentation/trace/hisi-ptt.rst new file mode 100644 index 0000000..f093846 --- /dev/null +++ b/Documentation/trace/hisi-ptt.rst @@ -0,0 +1,326 @@ [...] +On Kunpeng 930 SoC, the PCIe Root Complex is composed of several +PCIe cores. Each PCIe core includes several Root Ports and a PTT +RCiEP, like below. The PTT device is capable of tuning and +tracing the link of the PCIe core. +::
+--------------Core 0-------+| | [ PTT ] || | [Root Port]---[Endpoint]| | [Root Port]---[Endpoint]| | [Root Port]---[Endpoint]- Root Complex |------Core 1-------+
| | [ PTT ] || | [Root Port]---[ Switch ]---[Endpoint]| | [Root Port]---[Endpoint] `-[Endpoint]| | [Root Port]---[Endpoint]+---------------------------++The PTT device driver cannot be loaded if debugfs is not mounted.
This can't be right can it? Obviously debugfs must be enabled but why mounted?
+Each PTT device will be presented under /sys/kernel/debugfs/hisi_ptt +as its root directory, with name of its BDF number. +::
- /sys/kernel/debug/hisi_ptt/<domain>:<bus>:<device>.<function>
+Tune +====
+PTT tune is designed for monitoring and adjusting PCIe link parameters (events). +Currently we support events in 4 classes. The scope of the events +covers the PCIe core to which the PTT device belongs.
+Each event is presented as a file under $(PTT root dir)/$(BDF)/tune, and +mostly a simple open/read/write/close cycle will be used to tune +the event. +::
- $ cd /sys/kernel/debug/hisi_ptt/$(BDF)/tune
- $ ls
- qos_tx_cpl qos_tx_np qos_tx_p
- tx_path_rx_req_alloc_buf_level
- tx_path_tx_req_alloc_buf_level
- $ cat qos_tx_dp
- 1
- $ echo 2 > qos_tx_dp
- $ cat qos_tx_dp
- 2
+Current value (numerical value) of the event can be simply read +from the file, and the desired value written to the file to tune.
I saw that this RFC asks about whether debugfs is an appropriate interface for the *tracing* capability of the platform. Have similar questions been raised about the tuning interfaces?
It looks to me like tuning could be handled entirely using sysfs attributes. I think trying to handle these mostly decoupled feature in the same place is likely to be a mistake.
Daniel.