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SCIF ring buffer is a single producer, single consumer byte stream ring buffer optimized for avoiding reads across the PCIe bus while adding the required barriers and hardware workarounds for the MIC Coprocessor. The ring buffer is used to implement a receive queue for SCIF driver messaging between two nodes and for byte stream messaging between SCIF endpoints. The existing in-kernel ring buffer was not reused since it has not been designed for our use across the PCIe bus where each node runs an independent OS. Each SCIF node has a receive queue for every other SCIF node, and each connected endpoint has a receive queue for messages from its peer. This pair of receive queues is referred to as a SCIF queue pair. Reviewed-by: Nikhil Rao <nikhil.rao@intel.com> Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com> Signed-off-by: Sudeep Dutt <sudeep.dutt@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
101 lines
4.0 KiB
C
101 lines
4.0 KiB
C
/*
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* Intel MIC Platform Software Stack (MPSS)
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*
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* This file is provided under a dual BSD/GPLv2 license. When using or
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* redistributing this file, you may do so under either license.
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*
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* GPL LICENSE SUMMARY
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*
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* Copyright(c) 2014 Intel Corporation.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* BSD LICENSE
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*
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* Copyright(c) 2014 Intel Corporation.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* * Neither the name of Intel Corporation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Intel SCIF driver.
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*/
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#ifndef SCIF_RB_H
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#define SCIF_RB_H
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/*
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* This file describes a general purpose, byte based ring buffer. Writers to the
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* ring buffer need to synchronize using a lock. The same is true for readers,
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* although in practice, the ring buffer has a single reader. It is lockless
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* between producer and consumer so it can handle being used across the PCIe
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* bus. The ring buffer ensures that there are no reads across the PCIe bus for
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* performance reasons. Two of these are used to form a single bidirectional
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* queue-pair across PCIe.
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*/
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/*
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* struct scif_rb - SCIF Ring Buffer
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*
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* @rb_base: The base of the memory used for storing RB messages
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* @read_ptr: Pointer to the read offset
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* @write_ptr: Pointer to the write offset
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* @size: Size of the memory in rb_base
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* @current_read_offset: Cached read offset for performance
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* @current_write_offset: Cached write offset for performance
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*/
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struct scif_rb {
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void *rb_base;
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u32 *read_ptr;
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u32 *write_ptr;
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u32 size;
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u32 current_read_offset;
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u32 current_write_offset;
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};
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/* methods used by both */
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void scif_rb_init(struct scif_rb *rb, u32 *read_ptr, u32 *write_ptr,
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void *rb_base, u8 size);
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/* writer only methods */
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/* write a new command, then scif_rb_commit() */
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int scif_rb_write(struct scif_rb *rb, void *msg, u32 size);
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/* after write(), then scif_rb_commit() */
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void scif_rb_commit(struct scif_rb *rb);
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/* query space available for writing to a RB. */
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u32 scif_rb_space(struct scif_rb *rb);
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/* reader only methods */
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/* read a new message from the ring buffer of size bytes */
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u32 scif_rb_get_next(struct scif_rb *rb, void *msg, u32 size);
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/* update the read pointer so that the space can be reused */
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void scif_rb_update_read_ptr(struct scif_rb *rb);
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/* count the number of bytes that can be read */
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u32 scif_rb_count(struct scif_rb *rb, u32 size);
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#endif
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