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NTB: switchtec_ntb: Update switchtec documentation with prerequisites for NTB 

The ntb_hw_switchtec driver has requirements on kernel configuration so add
these notes to the documentation and also clean up a few other sentences in
the documentation.

Signed-off-by: Wesley Yung <wesley.yung@microchip.com>
Signed-off-by: Kelvin Cao <kelvin.cao@microchip.com>
Signed-off-by: Wesley Sheng <wesley.sheng@microchip.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
hifive-unleashed-5.1
Wesley Yung 2018-10-10 22:42:55 +08:00 committed by Bjorn Helgaas
parent 742bbe1ee3
commit fb513f60ea
1 changed files with 20 additions and 10 deletions
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30
Documentation/switchtec.txt
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@ -23,7 +23,7 @@ The primary means of communicating with the Switchtec management firmware is
through the Memory-mapped Remote Procedure Call (MRPC) interface.
Commands are submitted to the interface with a 4-byte command
identifier and up to 1KB of command specific data. The firmware will
respond with a 4 bytes return code and up to 1KB of command specific
respond with a 4-byte return code and up to 1KB of command-specific
data. The interface only processes a single command at a time.
@ -36,8 +36,8 @@ device: /dev/switchtec#, one for each management endpoint in the system.
The char device has the following semantics:
* A write must consist of at least 4 bytes and no more than 1028 bytes.
The first four bytes will be interpreted as the command to run and
the remainder will be used as the input data. A write will send the
The first 4 bytes will be interpreted as the Command ID and the
remainder will be used as the input data. A write will send the
command to the firmware to begin processing.
* Each write must be followed by exactly one read. Any double write will
@ -45,9 +45,9 @@ The char device has the following semantics:
produce an error.
* A read will block until the firmware completes the command and return
the four bytes of status plus up to 1024 bytes of output data. (The
length will be specified by the size parameter of the read call --
reading less than 4 bytes will produce an error.
the 4-byte Command Return Value plus up to 1024 bytes of output
data. (The length will be specified by the size parameter of the read
call -- reading less than 4 bytes will produce an error.)
* The poll call will also be supported for userspace applications that
need to do other things while waiting for the command to complete.
@ -83,10 +83,20 @@ The following IOCTLs are also supported by the device:
Non-Transparent Bridge (NTB) Driver
===================================
An NTB driver is provided for the switchtec hardware in switchtec_ntb.
Currently, it only supports switches configured with exactly 2
partitions. It also requires the following configuration settings:
An NTB hardware driver is provided for the Switchtec hardware in
ntb_hw_switchtec. Currently, it only supports switches configured with
exactly 2 NT partitions and zero or more non-NT partitions. It also requires
the following configuration settings:
* Both partitions must be able to access each other's GAS spaces.
* Both NT partitions must be able to access each other's GAS spaces.
Thus, the bits in the GAS Access Vector under Management Settings
must be set to support this.
* Kernel configuration MUST include support for NTB (CONFIG_NTB needs
to be set)
NT EP BAR 2 will be dynamically configured as a Direct Window, and
the configuration file does not need to configure it explicitly.
Please refer to Documentation/ntb.txt in Linux source tree for an overall
understanding of the Linux NTB stack. ntb_hw_switchtec works as an NTB
Hardware Driver in this stack.