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There are lots of documents under Documentation/*.txt and a few other orphan documents elsehwere that belong to the driver-API book. Move them to their right place. Reviewed-by: Cornelia Huck <cohuck@redhat.com> # vfio-related parts Acked-by: Logan Gunthorpe <logang@deltatee.com> # switchtec Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
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Linux Switchtec Support
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========================
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Microsemi's "Switchtec" line of PCI switch devices is already
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supported by the kernel with standard PCI switch drivers. However, the
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Switchtec device advertises a special management endpoint which
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enables some additional functionality. This includes:
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* Packet and Byte Counters
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* Firmware Upgrades
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* Event and Error logs
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* Querying port link status
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* Custom user firmware commands
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The switchtec kernel module implements this functionality.
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Interface
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=========
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The primary means of communicating with the Switchtec management firmware is
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through the Memory-mapped Remote Procedure Call (MRPC) interface.
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Commands are submitted to the interface with a 4-byte command
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identifier and up to 1KB of command specific data. The firmware will
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respond with a 4-byte return code and up to 1KB of command-specific
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data. The interface only processes a single command at a time.
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Userspace Interface
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===================
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The MRPC interface will be exposed to userspace through a simple char
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device: /dev/switchtec#, one for each management endpoint in the system.
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The char device has the following semantics:
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* A write must consist of at least 4 bytes and no more than 1028 bytes.
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The first 4 bytes will be interpreted as the Command ID and the
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remainder will be used as the input data. A write will send the
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command to the firmware to begin processing.
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* Each write must be followed by exactly one read. Any double write will
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produce an error and any read that doesn't follow a write will
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produce an error.
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* A read will block until the firmware completes the command and return
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the 4-byte Command Return Value plus up to 1024 bytes of output
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data. (The length will be specified by the size parameter of the read
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call -- reading less than 4 bytes will produce an error.)
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* The poll call will also be supported for userspace applications that
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need to do other things while waiting for the command to complete.
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The following IOCTLs are also supported by the device:
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* SWITCHTEC_IOCTL_FLASH_INFO - Retrieve firmware length and number
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of partitions in the device.
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* SWITCHTEC_IOCTL_FLASH_PART_INFO - Retrieve address and lengeth for
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any specified partition in flash.
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* SWITCHTEC_IOCTL_EVENT_SUMMARY - Read a structure of bitmaps
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indicating all uncleared events.
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* SWITCHTEC_IOCTL_EVENT_CTL - Get the current count, clear and set flags
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for any event. This ioctl takes in a switchtec_ioctl_event_ctl struct
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with the event_id, index and flags set (index being the partition or PFF
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number for non-global events). It returns whether the event has
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occurred, the number of times and any event specific data. The flags
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can be used to clear the count or enable and disable actions to
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happen when the event occurs.
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By using the SWITCHTEC_IOCTL_EVENT_FLAG_EN_POLL flag,
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you can set an event to trigger a poll command to return with
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POLLPRI. In this way, userspace can wait for events to occur.
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* SWITCHTEC_IOCTL_PFF_TO_PORT and SWITCHTEC_IOCTL_PORT_TO_PFF convert
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between PCI Function Framework number (used by the event system)
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and Switchtec Logic Port ID and Partition number (which is more
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user friendly).
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Non-Transparent Bridge (NTB) Driver
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===================================
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An NTB hardware driver is provided for the Switchtec hardware in
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ntb_hw_switchtec. Currently, it only supports switches configured with
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exactly 2 NT partitions and zero or more non-NT partitions. It also requires
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the following configuration settings:
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* Both NT partitions must be able to access each other's GAS spaces.
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Thus, the bits in the GAS Access Vector under Management Settings
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must be set to support this.
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* Kernel configuration MUST include support for NTB (CONFIG_NTB needs
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to be set)
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NT EP BAR 2 will be dynamically configured as a Direct Window, and
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the configuration file does not need to configure it explicitly.
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Please refer to Documentation/driver-api/ntb.rst in Linux source tree for an overall
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understanding of the Linux NTB stack. ntb_hw_switchtec works as an NTB
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Hardware Driver in this stack.
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