linux_dsm_epyc7002/Documentation/rapidio/tsi721.txt

RapidIO subsystem mport driver for IDT Tsi721 PCI Express-to-SRIO bridge.
=========================================================================

I. Overview

This driver implements all currently defined RapidIO mport callback functions.
It supports maintenance read and write operations, inbound and outbound RapidIO
doorbells, inbound maintenance port-writes and RapidIO messaging.

To generate SRIO maintenance transactions this driver uses one of Tsi721 DMA
channels. This mechanism provides access to larger range of hop counts and
destination IDs without need for changes in outbound window translation.

RapidIO messaging support uses dedicated messaging channels for each mailbox.
For inbound messages this driver uses destination ID matching to forward messages
into the corresponding message queue. Messaging callbacks are implemented to be
fully compatible with RIONET driver (Ethernet over RapidIO messaging services).

II. Known problems

  None.

III. DMA Engine Support

Tsi721 mport driver supports DMA data transfers between local system memory and
remote RapidIO devices. This functionality is implemented according to SLAVE
mode API defined by common Linux kernel DMA Engine framework.

Depending on system requirements RapidIO DMA operations can be included/excluded
by setting CONFIG_RAPIDIO_DMA_ENGINE option. Tsi721 miniport driver uses seven
out of eight available BDMA channels to support DMA data transfers.
One BDMA channel is reserved for generation of maintenance read/write requests.

If Tsi721 mport driver have been built with RAPIDIO_DMA_ENGINE support included,
this driver will accept DMA-specific module parameter:
  "dma_desc_per_channel" - defines number of hardware buffer descriptors used by
                           each BDMA channel of Tsi721 (by default - 128).

IV. Version History

  1.1.0 - DMA operations re-worked to support data scatter/gather lists larger
          than hardware buffer descriptors ring.
  1.0.0 - Initial driver release.

V.  License
-----------------------------------------------

  Copyright(c) 2011 Integrated Device Technology, Inc. All rights reserved.

  This program is free software; you can redistribute it and/or modify it
  under the terms of the GNU General Public License as published by the Free
  Software Foundation; either version 2 of the License, or (at your option)
  any later version.

  This program is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  more details.

  You should have received a copy of the GNU General Public License along with
  this program; if not, write to the Free Software Foundation, Inc.,
  59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.