54 lines
2 KiB
Text
54 lines
2 KiB
Text
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========================
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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 bytes 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 four bytes will be interpreted as the command to run and
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the 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 four bytes of status plus up to 1024 bytes of output data. (The
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length will be specified by the size parameter of the read call --
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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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