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.