| .. 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 |
| [...] |
