0e6af7b9e9
which is able to manipulate the clock and data lines directly. When an i2c bus is hung by a slave device stuck in the middle of a transaction that didn't complete properly, this function manipulates the clock and data lines in a sequence known to reliably reset slave devices. The most common cause of a hung i2c bus is a system reboot in the middle of an i2c transfer (so it doesnt' happen often, but now there is a way other than power cycling to recover from it).
58 lines
2.2 KiB
C
58 lines
2.2 KiB
C
/*-
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* Copyright (c) 2017 Ian Lepore <ian@freebsd.org>
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* All rights reserved.
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*
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* Development sponsored by Microsemi, Inc.
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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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* 1. 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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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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/*
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* Helper code to recover a hung i2c bus by bit-banging a recovery sequence.
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*/
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#ifndef _IICBUS_IIC_RECOVER_BUS_H_
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#define _IICBUS_IIC_RECOVER_BUS_H_
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struct iicrb_pin_access {
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void *ctx;
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int (*getsda)(void *ctx);
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void (*setsda)(void *ctx, int value);
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int (*getscl)(void *ctx);
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void (*setscl)(void *ctx, int value);
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};
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/*
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* Drive the bus-recovery logic by manipulating the line states using the
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* caller-provided functions. This does not block or sleep or acquire any locks
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* (unless the provided pin access functions do so). It uses DELAY() to pace
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* bits on the bus.
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*
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* Returns 0 if the bus is functioning properly or IIC_EBUSERR if the recovery
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* attempt failed and some slave device is still driving the bus.
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*/
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int iic_recover_bus(struct iicrb_pin_access *pins);
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#endif
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