844aff82a6
The current support for controlling i2c bus speed is an inconsistant mess. There are 4 symbolic speed values defined, UNKNOWN, SLOW, FAST, FASTEST. It seems to be universally assumed that SLOW means the standard 100KHz rate from the original spec. Nothing ever calls iicbus_reset() with a speed of FAST, although some drivers would treat it as the 400KHz standard speed. Mostly iicbus_reset() is called with the speed set to UNKNOWN or FASTEST, and there's really no telling what any individual driver will do with those. The speed of an i2c bus is limited by the speed of the slowest device on the bus. This means that generally the bus speed needs to be configured based on the board/system and the components within it. Historically for i2c we've configured with device hints. Newer systems use FDT data and it documents a clock-frequency property for i2c busses. Hobbyists and developers are likely to want on the fly changes. These changes provide all 3 methods, but do not require any existing drivers to change to use the new facilities. This adds an iicbus method, iicbus_get_frequency(dev, speed) that gets the frequency for the requested symbolic speed. If the symbolic speed is SLOW or if there is no speed configured for the bus, the returned value is 100KHz, always. Otherwise, if bus speed is configured by hints, fdt, tunable, or sysctl, that speed is returned. It also adds a helper function, iicbus_init_frequency() that any bus driver subclassed from iicbus can initialize the frequency from some other source of info. Initial driver implementations are provided for Freescale and TI. Differential Revision: https://reviews.freebsd.org/D1174 PR: 195009
138 lines
2.7 KiB
Objective-C
138 lines
2.7 KiB
Objective-C
#-
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# Copyright (c) 1998 Nicolas Souchu
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# All rights reserved.
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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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#include <sys/bus.h>
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#include <dev/iicbus/iic.h>
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INTERFACE iicbus;
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CODE {
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static u_int
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iicbus_default_frequency(device_t bus, u_char speed)
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{
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return (100000);
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}
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};
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#
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# Interpret interrupt
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#
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METHOD int intr {
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device_t dev;
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int event;
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char *buf;
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};
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#
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# iicbus callback
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#
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METHOD int callback {
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device_t dev;
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int index;
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caddr_t data;
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};
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#
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# Send REPEATED_START condition
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#
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METHOD int repeated_start {
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device_t dev;
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u_char slave;
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int timeout;
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};
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#
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# Send START condition
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#
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METHOD int start {
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device_t dev;
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u_char slave;
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int timeout;
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};
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#
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# Send STOP condition
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#
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METHOD int stop {
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device_t dev;
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};
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#
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# Read from I2C bus
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#
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METHOD int read {
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device_t dev;
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char *buf;
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int len;
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int *bytes;
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int last;
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int delay;
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};
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#
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# Write to the I2C bus
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#
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METHOD int write {
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device_t dev;
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const char *buf;
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int len;
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int *bytes;
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int timeout;
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};
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#
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# Reset I2C bus
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#
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METHOD int reset {
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device_t dev;
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u_char speed;
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u_char addr;
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u_char *oldaddr;
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};
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#
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# Generalized Read/Write interface
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#
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METHOD int transfer {
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device_t dev;
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struct iic_msg *msgs;
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uint32_t nmsgs;
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};
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#
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# Return the frequency in Hz for the bus running at the given
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# symbolic speed. Only the IIC_SLOW speed has meaning, it is always
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# 100KHz. The UNKNOWN, FAST, and FASTEST rates all map to the
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# configured bus frequency, or 100KHz when not otherwise configured.
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#
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METHOD u_int get_frequency {
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device_t dev;
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u_char speed;
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} DEFAULT iicbus_default_frequency;
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