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a430556ecb
Add an i2c mux driver providing access to i2c bus segments using a
hardware MUX sitting on a master bus and controlled through gpio pins.
E.G. something like:
---------- ---------- Bus segment 1 - - - - -
| | SCL/SDA | |-------------- | |
| |------------| |
| | | | Bus segment 2 | |
| Linux | GPIO 1..N | MUX |--------------- Devices
| |------------| | | |
| | | | Bus segment M
| | | |---------------| |
---------- ---------- - - - - -
SCL/SDA of the master I2C bus is multiplexed to bus segment 1..M
according to the settings of the GPIO pins 1..N.
Note commit log from kernel
commit 92ed1a76("i2c: Add generic I2C multiplexer using GPIO API")
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Tested-by: Peng Fan <peng.fan@nxp.com> (i.MX6QP-Sabreauto)
Cc: Heiko Schocher <hs@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Simon Glass <sjg@chromium.org>
139 lines
2.9 KiB
C
139 lines
2.9 KiB
C
/*
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* I2C multiplexer using GPIO API
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*
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* Copyright 2017 NXP
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*
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* Peng Fan <peng.fan@nxp.com>
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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#include <asm/io.h>
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#include <asm-generic/gpio.h>
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#include <common.h>
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#include <dm.h>
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#include <dm/pinctrl.h>
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#include <fdtdec.h>
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#include <i2c.h>
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#include <linux/errno.h>
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DECLARE_GLOBAL_DATA_PTR;
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/**
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* struct i2c_mux_gpio_priv - private data for i2c mux gpio
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*
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* @values: the reg value of each child node
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* @n_values: num of regs
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* @gpios: the mux-gpios array
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* @n_gpios: num of gpios in mux-gpios
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* @idle: the value of idle-state
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*/
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struct i2c_mux_gpio_priv {
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u32 *values;
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int n_values;
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struct gpio_desc *gpios;
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int n_gpios;
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u32 idle;
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};
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static int i2c_mux_gpio_select(struct udevice *dev, struct udevice *bus,
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uint channel)
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{
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struct i2c_mux_gpio_priv *priv = dev_get_priv(dev);
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int i, ret;
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for (i = 0; i < priv->n_gpios; i++) {
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ret = dm_gpio_set_value(&priv->gpios[i], (channel >> i) & 1);
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if (ret)
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return ret;
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}
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return 0;
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}
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static int i2c_mux_gpio_deselect(struct udevice *dev, struct udevice *bus,
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uint channel)
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{
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struct i2c_mux_gpio_priv *priv = dev_get_priv(dev);
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int i, ret;
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for (i = 0; i < priv->n_gpios; i++) {
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ret = dm_gpio_set_value(&priv->gpios[i], (priv->idle >> i) & 1);
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if (ret)
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return ret;
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}
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return 0;
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}
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static int i2c_mux_gpio_probe(struct udevice *dev)
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{
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const void *fdt = gd->fdt_blob;
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int node = dev_of_offset(dev);
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struct i2c_mux_gpio_priv *mux = dev_get_priv(dev);
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struct gpio_desc *gpios;
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u32 *values;
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int i = 0, subnode, ret;
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mux->n_values = fdtdec_get_child_count(fdt, node);
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values = devm_kzalloc(dev, sizeof(*mux->values) * mux->n_values,
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GFP_KERNEL);
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if (!values) {
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dev_err(dev, "Cannot alloc values array");
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return -ENOMEM;
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}
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fdt_for_each_subnode(subnode, fdt, node) {
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*(values + i) = fdtdec_get_uint(fdt, subnode, "reg", -1);
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i++;
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}
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mux->values = values;
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mux->idle = fdtdec_get_uint(fdt, node, "idle-state", -1);
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mux->n_gpios = gpio_get_list_count(dev, "mux-gpios");
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if (mux->n_gpios < 0) {
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dev_err(dev, "Missing mux-gpios property\n");
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return -EINVAL;
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}
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gpios = devm_kzalloc(dev, sizeof(struct gpio_desc) * mux->n_gpios,
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GFP_KERNEL);
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if (!gpios) {
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dev_err(dev, "Cannot allocate gpios array\n");
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return -ENOMEM;
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}
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ret = gpio_request_list_by_name(dev, "mux-gpios", gpios, mux->n_gpios,
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GPIOD_IS_OUT_ACTIVE);
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if (ret <= 0) {
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dev_err(dev, "Failed to request mux-gpios\n");
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return ret;
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}
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mux->gpios = gpios;
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return 0;
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}
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static const struct i2c_mux_ops i2c_mux_gpio_ops = {
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.select = i2c_mux_gpio_select,
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.deselect = i2c_mux_gpio_deselect,
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};
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static const struct udevice_id i2c_mux_gpio_ids[] = {
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{ .compatible = "i2c-mux-gpio", },
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{}
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};
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U_BOOT_DRIVER(i2c_mux_gpio) = {
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.name = "i2c_mux_gpio",
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.id = UCLASS_I2C_MUX,
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.of_match = i2c_mux_gpio_ids,
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.ops = &i2c_mux_gpio_ops,
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.probe = i2c_mux_gpio_probe,
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.priv_auto_alloc_size = sizeof(struct i2c_mux_gpio_priv),
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};
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