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diff --git a/Documentation/trace/hisi-ptt.rst b/Documentation/trace/hisi-ptt.rst new file mode 100644 index 000000000..4f87d8e21 --- /dev/null +++ b/Documentation/trace/hisi-ptt.rst @@ -0,0 +1,298 @@ +.. 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 links 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 registers one PMU device for each PTT 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 2 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 +a simple open/read/write/close cycle will be used to tune 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. + +- rx_alloc_buf_level: watermark of Rx requested +- tx_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 transmitted either when the +watermark 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 illustrated later. +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 Endpoint, which are located on the same core of the PTT device. You can +set the filter by specifying the `filter` parameter which is required to start +the trace. The parameter value is 20 bit. Bit 19 indicates the filter type. +1 for Root Port filter and 0 for Requester filter. Bit[15:0] indicates the +filter value. The value for a Root Port is a mask of the core port id which is +calculated from its PCI Slot ID as (slotid & 7) * 2. The value for a Requester +is the Requester ID (Device ID of the PCIe function). Bit[18:16] is currently +reserved for extension. + +For example, if the desired filter is Endpoint function 0000:01:00.1 the filter +value will be 0x00101. If the desired filter is Root Port 0000:00:10.0 then +then filter value is calculated as 0x80001. + +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. Driver maintains a list of +available filters and will check the invalid inputs. + +Currently the available filters are detected in driver's probe. If the supported +devices are removed/added after probe, you may need to reload the driver to update +the filters. + +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 classified into two types: + +- 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. 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. + +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 + [...] |