switchtec.rst (4120B)
1======================== 2Linux Switchtec Support 3======================== 4 5Microsemi's "Switchtec" line of PCI switch devices is already 6supported by the kernel with standard PCI switch drivers. However, the 7Switchtec device advertises a special management endpoint which 8enables some additional functionality. This includes: 9 10* Packet and Byte Counters 11* Firmware Upgrades 12* Event and Error logs 13* Querying port link status 14* Custom user firmware commands 15 16The switchtec kernel module implements this functionality. 17 18 19Interface 20========= 21 22The primary means of communicating with the Switchtec management firmware is 23through the Memory-mapped Remote Procedure Call (MRPC) interface. 24Commands are submitted to the interface with a 4-byte command 25identifier and up to 1KB of command specific data. The firmware will 26respond with a 4-byte return code and up to 1KB of command-specific 27data. The interface only processes a single command at a time. 28 29 30Userspace Interface 31=================== 32 33The MRPC interface will be exposed to userspace through a simple char 34device: /dev/switchtec#, one for each management endpoint in the system. 35 36The char device has the following semantics: 37 38* A write must consist of at least 4 bytes and no more than 1028 bytes. 39 The first 4 bytes will be interpreted as the Command ID and the 40 remainder will be used as the input data. A write will send the 41 command to the firmware to begin processing. 42 43* Each write must be followed by exactly one read. Any double write will 44 produce an error and any read that doesn't follow a write will 45 produce an error. 46 47* A read will block until the firmware completes the command and return 48 the 4-byte Command Return Value plus up to 1024 bytes of output 49 data. (The length will be specified by the size parameter of the read 50 call -- reading less than 4 bytes will produce an error.) 51 52* The poll call will also be supported for userspace applications that 53 need to do other things while waiting for the command to complete. 54 55The following IOCTLs are also supported by the device: 56 57* SWITCHTEC_IOCTL_FLASH_INFO - Retrieve firmware length and number 58 of partitions in the device. 59 60* SWITCHTEC_IOCTL_FLASH_PART_INFO - Retrieve address and lengeth for 61 any specified partition in flash. 62 63* SWITCHTEC_IOCTL_EVENT_SUMMARY - Read a structure of bitmaps 64 indicating all uncleared events. 65 66* SWITCHTEC_IOCTL_EVENT_CTL - Get the current count, clear and set flags 67 for any event. This ioctl takes in a switchtec_ioctl_event_ctl struct 68 with the event_id, index and flags set (index being the partition or PFF 69 number for non-global events). It returns whether the event has 70 occurred, the number of times and any event specific data. The flags 71 can be used to clear the count or enable and disable actions to 72 happen when the event occurs. 73 By using the SWITCHTEC_IOCTL_EVENT_FLAG_EN_POLL flag, 74 you can set an event to trigger a poll command to return with 75 POLLPRI. In this way, userspace can wait for events to occur. 76 77* SWITCHTEC_IOCTL_PFF_TO_PORT and SWITCHTEC_IOCTL_PORT_TO_PFF convert 78 between PCI Function Framework number (used by the event system) 79 and Switchtec Logic Port ID and Partition number (which is more 80 user friendly). 81 82 83Non-Transparent Bridge (NTB) Driver 84=================================== 85 86An NTB hardware driver is provided for the Switchtec hardware in 87ntb_hw_switchtec. Currently, it only supports switches configured with 88exactly 2 NT partitions and zero or more non-NT partitions. It also requires 89the following configuration settings: 90 91* Both NT partitions must be able to access each other's GAS spaces. 92 Thus, the bits in the GAS Access Vector under Management Settings 93 must be set to support this. 94* Kernel configuration MUST include support for NTB (CONFIG_NTB needs 95 to be set) 96 97NT EP BAR 2 will be dynamically configured as a Direct Window, and 98the configuration file does not need to configure it explicitly. 99 100Please refer to Documentation/driver-api/ntb.rst in Linux source tree for an overall 101understanding of the Linux NTB stack. ntb_hw_switchtec works as an NTB 102Hardware Driver in this stack.