On Mon, 24 Jan 2022 21:11:16 +0800 Yicong Yang <yangyicong@xxxxxxxxxxxxx> wrote: > Document the introduction and usage of HiSilicon PTT device driver. > > Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx> Nice document. A few trivial typos inline. I would give a RB except I've suggested you change a part of the sysfs interface which will affect the relevant documentation. Thanks, Jonathan > --- > Documentation/trace/hisi-ptt.rst | 304 +++++++++++++++++++++++++++++++ > 1 file changed, 304 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 000000000000..f3269b11a2f6 > --- /dev/null > +++ b/Documentation/trace/hisi-ptt.rst > @@ -0,0 +1,304 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +====================================== > +HiSilicon PCIe Tune and Trace device > +====================================== > + > +Introduction > +============ > + > +HiSilicon PCIe tune and trace device (PTT) is a PCIe Root Complex > +integrated Endpoint (RCiEP) device, providing the capability > +to dynamically monitor and tune the PCIe link's events (tune), > +and trace the TLP headers (trace). The two functions are independent, > +but is recommended to use them together to analyze and enhance the > +PCIe link's performance. > + > +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. links > +:: > + +--------------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 registers PMU device for each PTT device. registers one PMU device .. > +The name of each PTT device is composed of 'hisi_ptt' prefix with > +the id of the SICL and the Core where it locates. The Kunpeng 930 > +SoC encapsulates multiple CPU dies (SCCL, Super CPU Cluster) and > +IO dies (SICL, Super I/O Cluster), where there's one PCIe Root > +Complex for each SICL. > +:: > + /sys/devices/hisi_ptt<sicl_id>_<core_id> > + > +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 PMU dir)/tune, and > +mostly a simple open/read/write/close cycle will be used to tune drop "mostly" as it doesn't add anything other than potential confusion. > +the event. > +:: > + $ cd /sys/devices/hisi_ptt<sicl_id>_<core_id>/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. > + > +1. Tx path QoS control > +------------------------ > + > +The following files are provided to tune the QoS of the tx path of > +the PCIe core. > + > +- qos_tx_cpl: weight of Tx completion TLPs > +- qos_tx_np: weight of Tx non-posted TLPs > +- qos_tx_p: weight of Tx posted TLPs > + > +The weight influences the proportion of certain packets on the PCIe link. > +For example, for the storage scenario, increase the proportion > +of the completion packets on the link to enhance the performance as > +more completions are consumed. > + > +The available tune data of these events is [0, 1, 2]. > +Writing a negative value will return an error, and out of range > +values will be converted to 2. Note that the event value just > +indicates a probable level, but is not precise. > + > +2. Tx path buffer control > +------------------------- > + > +Following files are provided to tune the buffer of tx path of the PCIe core. > + > +- tx_path_rx_req_alloc_buf_level: watermark of Rx requested > +- tx_path_tx_req_alloc_buf_level: watermark of Tx requested > + > +These events influence the watermark of the buffer allocated for each > +type. Rx means the inbound while Tx means outbound. The packets will > +be stored in the buffer first and then posted either when the watermark Change "posted" to "transmitted" as posted has a special meaning in PCI and I don't think that is what you mean here... (I could be wrong!) > +reached or when timed out. For a busy direction, you should increase > +the related buffer watermark to avoid frequently posting and thus > +enhance the performance. In most cases just keep the default value. > + > +The available tune data of above events is [0, 1, 2]. > +Writing a negative value will return an error, and out of range > +values will be converted to 2. Note that the event value just > +indicates a probable level, but is not precise. > + > +Trace > +===== > + > +PTT trace is designed for dumping the TLP headers to the memory, which > +can be used to analyze the transactions and usage condition of the PCIe > +Link. You can choose to filter the traced headers by either requester ID, > +or those downstream of a set of Root Ports on the same core of the PTT > +device. It's also supported to trace the headers of certain type and of > +certain direction. > + > +You can use the perf command `perf record` to set the parameters, start > +trace and get the data. It's also supported to decode the trace > +data with `perf report`. The control parameters for trace is inputted > +as event code for each events, which will be further illustracted later. illustrated > +An example usage is like > +:: > + $ perf record -e hisi_ptt0_2/filter=0x80001,type=1,direction=1, > + format=1/ -- sleep 5 > + > +This will trace the TLP headers downstream root port 0000:00:10.1 (event > +code for event 'filter' is 0x80001) with type of posted TLP requests, > +direction of inbound and traced data format of 8DW. > + > +1. filter > +--------- > + > +The TLP headers to trace can be filtered by the Root Ports or the requester > +ID of the endpoints, which are locates on the same core of the PTT device. located > +You can set the filter by spedifying the `filter` parameter which is required > +to start the trace. The parameter value is 20 bit. The supported filters and > +related values is outputted through `available_filters` sysfs attribute > +under related PTT PMU directory, classified as Root Ports and Requesters > +respectively. > +:: > + $ cat available_filters > + #### Root Ports #### > + 0000:00:10.0 0x80001 > + 0000:00:11.0 0x80004 > + #### Requesters #### > + 0000:01:00.0 0x00100 > + 0000:01:00.1 0x00101 > + > +Note that multiple Root Ports can be specified at one time, but only > +one Endpoint function can be specified in one trace. Specifying both > +Root Port and function at the same time is not supported. > + > +If no filter is available, reading the available_filters will get the hint. > +:: > + $ cat available_filters > + #### No available filter #### If you take not of my earlier feedback this bit may change slightly. > + > +The available_filters can be dynamically updated, which means you can always > +get correct filter information when hotplug events happen, or when you manually > +remove/rescan the devices. > + > +2. type > +------- > + > +You can trace the TLP headers of certain types by specifying the `type` > +parameter, which is required to start the trace. The parameter value is > +8 bit. Current supported types and related values are shown below: > + > +8'b00000001: posted requests (P) > +8'b00000010: non-posted requests (NP) > +8'b00000100: completions (CPL) > + > +You can specify multiple types when tracing inbound TLP headers, but can only > +specify one when tracing outbound TLP headers. > + > +3. direction > +------------ > + > +You can trace the TLP headers from certain direction, which is relative > +to the Root Port or the PCIe core, by specifying the `direction` parameter. > +This is optional and the default parameter is inbound. The parameter value > +is 4 bit. When the desired format is 4DW, directions and related values > +supported are shown below: > + > +4'b0000: inbound TLPs (P, NP, CPL) > +4'b0001: outbound TLPs (P, NP, CPL) > +4'b0010: outbound TLPs (P, NP, CPL) and inbound TLPs (P, NP, CPL B) > +4'b0011: outbound TLPs (P, NP, CPL) and inbound TLPs (CPL A) > + > +When the desired format is 8DW, directions and related values supported are > +shown below: > + > +4'b0000: reserved > +4'b0001: outbound TLPs (P, NP, CPL) > +4'b0010: inbound TLPs (P, NP, CPL B) > +4'b0011: inbound TLPs (CPL A) > + > +Inbound completions are classifed into two types: classified > + > +completion A (CPL A): completion of CHI/DMA/Native non-posted requests, except for CPL B > +completion B (CPL B): completion of DMA remote2local and P2P non-posted requests > + > +4. format > +-------------- > + > +You can change the format of the traced TLP headers by specifying the > +`format` parameter. This is optional and the default format is 4DW. As there is a default, there is no need to also say it is optional. `format parameter. The default format is 4DW. > +The parameter value is 4 bit. Current supported formats and related > +values are shown below: > + > +4'b0000: 4DW length per TLP header > +4'b0001: 8DW length per TLP header > + > +The traced TLP header format is different from the PCIe standard. > + > +When using the 8DW data format, the entire TLP header is logged > +(Header DW0-3 shown below). For example, the TLP header for Memory > +Reads with 64-bit addresses is shown in PCIe r5.0, Figure 2-17; > +the header for Configuration Requests is shown in Figure 2.20, etc. > + > +In addition, 8DW trace buffer entries contain a timestamp and > +possibly a prefix for a PASID TLP prefix (see Figure 6-20, PCIe r5.0). > +Otherwise this field will be all 0. > + > +The bit[31:11] of DW0 is always 0x1fffff, which can be > +used to distinguish the data format. 8DW format is like > +:: > + bits [ 31:11 ][ 10:0 ] > + |---------------------------------------|-------------------| > + DW0 [ 0x1fffff ][ Reserved (0x7ff) ] > + DW1 [ Prefix ] > + DW2 [ Header DW0 ] > + DW3 [ Header DW1 ] > + DW4 [ Header DW2 ] > + DW5 [ Header DW3 ] > + DW6 [ Reserved (0x0) ] > + DW7 [ Time ] > + > +When using the 4DW data format, DW0 of the trace buffer entry > +contains selected fields of DW0 of the TLP, together with a > +timestamp. DW1-DW3 of the trace buffer entry contain DW1-DW3 > +directly from the TLP header. > + > +4DW format is like > +:: > + bits [31:30] [ 29:25 ][24][23][22][21][ 20:11 ][ 10:0 ] > + |-----|---------|---|---|---|---|-------------|-------------| > + DW0 [ Fmt ][ Type ][T9][T8][TH][SO][ Length ][ Time ] > + DW1 [ Header DW1 ] > + DW2 [ Header DW2 ] > + DW3 [ Header DW3 ] > + > +5. memory management > +-------------------- > + > +The traced TLP headers will be written to the memory allocated > +by the driver. The hardware accepts 4 DMA address with same size, > +and writes the buffer sequentially like below. If DMA addr 3 is > +finished and the trace is still on, it will return to addr 0. > +:: > + +->[DMA addr 0]->[DMA addr 1]->[DMA addr 2]->[DMA addr 3]-+ > + +---------------------------------------------------------+ > + > +Driver will allocate each DMA buffer of 4MiB. The finished buffer > +will be copied to the perf AUX buffer allocated by the perf core. > +Once the AUX buffer is full while the trace is still on, driver > +will commit the AUX buffer first and then apply for a new one with > +the same size. The size of AUX buffer is default to 16MiB. User can > +adjust the size by specifying the `-m` parameter of the perf command. > + > +Note that there is a gap between committing the old AUX buffer and > +applying a new one, which means the trace is stopped during the > +moment and TLPs transferred in the moment cannot be traced. To avoid > +this situation, you should begin the trace with large AUX buffer > +enough to avoid this gap. > + > +6. decoding > +----------- > + > +You can decode the traced data with `perf report -D` command (currently > +only support to dump the raw trace data). The traced data will be decoded > +according to the format described previously (take 8DW as an example): > +:: > + [...perf headers and other information] > + . ... HISI PTT data: size 4194304 bytes > + . 00000000: 00 00 00 00 Prefix > + . 00000004: 01 00 00 60 Header DW0 > + . 00000008: 0f 1e 00 01 Header DW1 > + . 0000000c: 04 00 00 00 Header DW2 > + . 00000010: 40 00 81 02 Header DW3 > + . 00000014: 33 c0 04 00 Time > + . 00000020: 00 00 00 00 Prefix > + . 00000024: 01 00 00 60 Header DW0 > + . 00000028: 0f 1e 00 01 Header DW1 > + . 0000002c: 04 00 00 00 Header DW2 > + . 00000030: 40 00 81 02 Header DW3 > + . 00000034: 02 00 00 00 Time > + . 00000040: 00 00 00 00 Prefix > + . 00000044: 01 00 00 60 Header DW0 > + . 00000048: 0f 1e 00 01 Header DW1 > + . 0000004c: 04 00 00 00 Header DW2 > + . 00000050: 40 00 81 02 Header DW3 > + [...]
