i2c: mux: demux-pinctrl: add driver
This driver allows an I2C bus to switch between multiple masters. This is not hot-switching because connected I2C slaves will be re-instantiated. It is meant to select the best I2C core at runtime once the task is known. Example: Prefer i2c-gpio over another I2C core because of HW errata affecting your use case. Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Wolfram Sang
Wolfram Sang
parent
388f7b1d6e
commit
50a5ba8769
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@ -0,0 +1,23 @@
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What: /sys/devices/platform/<i2c-demux-name>/cur_master
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Date: January 2016
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KernelVersion: 4.6
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Contact: Wolfram Sang <wsa@the-dreams.de>
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Description:
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This file selects the active I2C master for a demultiplexed bus.
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Write 0 there for the first master, 1 for the second etc. Reading the file will
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give you a list with the active master marked. Example from a Renesas Lager
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board:
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root@Lager:~# cat /sys/devices/platform/i2c@8/cur_master
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* 0 - /i2c@9
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1 - /i2c@e6520000
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2 - /i2c@e6530000
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root@Lager:~# echo 2 > /sys/devices/platform/i2c@8/cur_master
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root@Lager:~# cat /sys/devices/platform/i2c@8/cur_master
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0 - /i2c@9
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1 - /i2c@e6520000
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* 2 - /i2c@e6530000
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@ -0,0 +1,135 @@
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Pinctrl-based I2C Bus DeMux
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This binding describes an I2C bus demultiplexer that uses pin multiplexing to
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route the I2C signals, and represents the pin multiplexing configuration using
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the pinctrl device tree bindings. This may be used to select one I2C IP core at
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runtime which may have a better feature set for a given task than another I2C
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IP core on the SoC. The most simple example is to fall back to GPIO bitbanging
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if your current runtime configuration hits an errata of the internal IP core.
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+-------------------------------+
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| SoC |
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| | +-----+ +-----+
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| +------------+ | | dev | | dev |
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| |I2C IP Core1|--\ | +-----+ +-----+
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| +------------+ \-------+ | | |
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| |Pinctrl|--|------+--------+
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| +------------+ +-------+ |
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| |I2C IP Core2|--/ |
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| +------------+ |
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| |
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+-------------------------------+
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Required properties:
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- compatible: "i2c-demux-pinctrl"
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- i2c-parent: List of phandles of I2C masters available for selection. The first
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one will be used as default.
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- i2c-bus-name: The name of this bus. Also needed as pinctrl-name for the I2C
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parents.
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Furthermore, I2C mux properties and child nodes. See mux.txt in this directory.
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Example:
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Here is a snipplet for a bus to be demuxed. It contains various i2c clients for
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HDMI, so the bus is named "i2c-hdmi":
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i2chdmi: i2c@8 {
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compatible = "i2c-demux-pinctrl";
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i2c-parent = <&gpioi2c>, <&iic2>, <&i2c2>;
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i2c-bus-name = "i2c-hdmi";
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#address-cells = <1>;
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#size-cells = <0>;
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ak4643: sound-codec@12 {
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compatible = "asahi-kasei,ak4643";
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#sound-dai-cells = <0>;
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reg = <0x12>;
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};
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composite-in@20 {
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compatible = "adi,adv7180";
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reg = <0x20>;
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remote = <&vin1>;
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port {
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adv7180: endpoint {
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bus-width = <8>;
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remote-endpoint = <&vin1ep0>;
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};
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};
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};
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hdmi@39 {
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compatible = "adi,adv7511w";
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reg = <0x39>;
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interrupt-parent = <&gpio1>;
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interrupts = <15 IRQ_TYPE_LEVEL_LOW>;
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adi,input-depth = <8>;
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adi,input-colorspace = "rgb";
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adi,input-clock = "1x";
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adi,input-style = <1>;
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adi,input-justification = "evenly";
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ports {
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#address-cells = <1>;
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#size-cells = <0>;
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port@0 {
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reg = <0>;
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adv7511_in: endpoint {
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remote-endpoint = <&du_out_lvds0>;
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};
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};
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port@1 {
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reg = <1>;
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adv7511_out: endpoint {
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remote-endpoint = <&hdmi_con>;
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};
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};
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};
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};
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};
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And for clarification, here are the snipplets for the i2c-parents:
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gpioi2c: i2c@9 {
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#address-cells = <1>;
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#size-cells = <0>;
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compatible = "i2c-gpio";
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status = "disabled";
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gpios = <&gpio5 6 GPIO_ACTIVE_HIGH /* sda */
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&gpio5 5 GPIO_ACTIVE_HIGH /* scl */
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>;
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i2c-gpio,delay-us = <5>;
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};
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...
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&i2c2 {
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pinctrl-0 = <&i2c2_pins>;
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pinctrl-names = "i2c-hdmi";
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clock-frequency = <100000>;
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};
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...
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&iic2 {
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pinctrl-0 = <&iic2_pins>;
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pinctrl-names = "i2c-hdmi";
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clock-frequency = <100000>;
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};
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Please note:
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- pinctrl properties for the parent I2C controllers need a pinctrl state
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with the same name as i2c-bus-name, not "default"!
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- the i2c masters must have their status "disabled". This driver will
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enable them at runtime when needed.
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@ -72,4 +72,13 @@ config I2C_MUX_REG
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This driver can also be built as a module. If so, the module
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will be called i2c-mux-reg.
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config I2C_DEMUX_PINCTRL
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tristate "pinctrl-based I2C demultiplexer"
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depends on PINCTRL && OF
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select OF_DYNAMIC
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help
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If you say yes to this option, support will be included for an I2C
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demultiplexer that uses the pinctrl subsystem. This is useful if you
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want to change the I2C master at run-time depending on features.
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endmenu
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@ -3,6 +3,8 @@
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obj-$(CONFIG_I2C_ARB_GPIO_CHALLENGE) += i2c-arb-gpio-challenge.o
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obj-$(CONFIG_I2C_DEMUX_PINCTRL) += i2c-demux-pinctrl.o
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obj-$(CONFIG_I2C_MUX_GPIO) += i2c-mux-gpio.o
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obj-$(CONFIG_I2C_MUX_PCA9541) += i2c-mux-pca9541.o
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obj-$(CONFIG_I2C_MUX_PCA954x) += i2c-mux-pca954x.o
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@ -0,0 +1,272 @@
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/*
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* Pinctrl based I2C DeMultiplexer
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*
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* Copyright (C) 2015-16 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
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* Copyright (C) 2015-16 by Renesas Electronics Corporation
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; version 2 of the License.
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*
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* See the bindings doc for DTS setup and the sysfs doc for usage information.
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* (look for filenames containing 'i2c-demux-pinctrl' in Documentation/)
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*/
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#include <linux/i2c.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/of.h>
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#include <linux/pinctrl/consumer.h>
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#include <linux/platform_device.h>
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#include <linux/slab.h>
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#include <linux/sysfs.h>
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struct i2c_demux_pinctrl_chan {
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struct device_node *parent_np;
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struct i2c_adapter *parent_adap;
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struct of_changeset chgset;
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};
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struct i2c_demux_pinctrl_priv {
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int cur_chan;
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int num_chan;
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struct device *dev;
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const char *bus_name;
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struct i2c_adapter cur_adap;
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struct i2c_algorithm algo;
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struct i2c_demux_pinctrl_chan chan[];
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};
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static struct property status_okay = { .name = "status", .length = 3, .value = "ok" };
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static int i2c_demux_master_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
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{
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struct i2c_demux_pinctrl_priv *priv = adap->algo_data;
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struct i2c_adapter *parent = priv->chan[priv->cur_chan].parent_adap;
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return __i2c_transfer(parent, msgs, num);
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}
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static u32 i2c_demux_functionality(struct i2c_adapter *adap)
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{
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struct i2c_demux_pinctrl_priv *priv = adap->algo_data;
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struct i2c_adapter *parent = priv->chan[priv->cur_chan].parent_adap;
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return parent->algo->functionality(parent);
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}
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static int i2c_demux_activate_master(struct i2c_demux_pinctrl_priv *priv, u32 new_chan)
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{
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struct i2c_adapter *adap;
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struct pinctrl *p;
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int ret;
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ret = of_changeset_apply(&priv->chan[new_chan].chgset);
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if (ret)
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goto err;
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adap = of_find_i2c_adapter_by_node(priv->chan[new_chan].parent_np);
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if (!adap) {
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ret = -ENODEV;
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goto err;
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}
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p = devm_pinctrl_get_select(adap->dev.parent, priv->bus_name);
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if (IS_ERR(p)) {
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ret = PTR_ERR(p);
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goto err_with_put;
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}
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priv->chan[new_chan].parent_adap = adap;
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priv->cur_chan = new_chan;
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/* Now fill out current adapter structure. cur_chan must be up to date */
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priv->algo.master_xfer = i2c_demux_master_xfer;
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priv->algo.functionality = i2c_demux_functionality;
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snprintf(priv->cur_adap.name, sizeof(priv->cur_adap.name),
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"i2c-demux (master i2c-%d)", i2c_adapter_id(adap));
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priv->cur_adap.owner = THIS_MODULE;
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priv->cur_adap.algo = &priv->algo;
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priv->cur_adap.algo_data = priv;
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priv->cur_adap.dev.parent = priv->dev;
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priv->cur_adap.class = adap->class;
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priv->cur_adap.retries = adap->retries;
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priv->cur_adap.timeout = adap->timeout;
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priv->cur_adap.quirks = adap->quirks;
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priv->cur_adap.dev.of_node = priv->dev->of_node;
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ret = i2c_add_adapter(&priv->cur_adap);
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if (ret < 0)
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goto err_with_put;
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return 0;
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err_with_put:
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i2c_put_adapter(adap);
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err:
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dev_err(priv->dev, "failed to setup demux-adapter %d (%d)\n", new_chan, ret);
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return ret;
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}
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static int i2c_demux_deactivate_master(struct i2c_demux_pinctrl_priv *priv)
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{
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int ret, cur = priv->cur_chan;
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if (cur < 0)
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return 0;
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i2c_del_adapter(&priv->cur_adap);
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i2c_put_adapter(priv->chan[cur].parent_adap);
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ret = of_changeset_revert(&priv->chan[cur].chgset);
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priv->chan[cur].parent_adap = NULL;
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priv->cur_chan = -EINVAL;
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return ret;
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}
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static int i2c_demux_change_master(struct i2c_demux_pinctrl_priv *priv, u32 new_chan)
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{
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int ret;
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if (new_chan == priv->cur_chan)
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return 0;
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ret = i2c_demux_deactivate_master(priv);
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if (ret)
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return ret;
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return i2c_demux_activate_master(priv, new_chan);
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}
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static ssize_t cur_master_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct i2c_demux_pinctrl_priv *priv = dev_get_drvdata(dev);
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int count = 0, i;
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for (i = 0; i < priv->num_chan && count < PAGE_SIZE; i++)
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count += scnprintf(buf + count, PAGE_SIZE - count, "%c %d - %s\n",
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i == priv->cur_chan ? '*' : ' ', i,
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priv->chan[i].parent_np->full_name);
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return count;
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}
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static ssize_t cur_master_store(struct device *dev, struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct i2c_demux_pinctrl_priv *priv = dev_get_drvdata(dev);
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unsigned int val;
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int ret;
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ret = kstrtouint(buf, 0, &val);
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if (ret < 0)
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return ret;
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if (val >= priv->num_chan)
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return -EINVAL;
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ret = i2c_demux_change_master(priv, val);
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return ret < 0 ? ret : count;
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}
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static DEVICE_ATTR_RW(cur_master);
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static int i2c_demux_pinctrl_probe(struct platform_device *pdev)
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{
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struct device_node *np = pdev->dev.of_node;
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struct i2c_demux_pinctrl_priv *priv;
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int num_chan, i, j, err;
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num_chan = of_count_phandle_with_args(np, "i2c-parent", NULL);
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if (num_chan < 2) {
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dev_err(&pdev->dev, "Need at least two I2C masters to switch\n");
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return -EINVAL;
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}
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priv = devm_kzalloc(&pdev->dev, sizeof(*priv)
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+ num_chan * sizeof(struct i2c_demux_pinctrl_chan), GFP_KERNEL);
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if (!priv)
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return -ENOMEM;
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err = of_property_read_string(np, "i2c-bus-name", &priv->bus_name);
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if (err)
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return err;
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for (i = 0; i < num_chan; i++) {
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struct device_node *adap_np;
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adap_np = of_parse_phandle(np, "i2c-parent", i);
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if (!adap_np) {
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dev_err(&pdev->dev, "can't get phandle for parent %d\n", i);
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err = -ENOENT;
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goto err_rollback;
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}
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priv->chan[i].parent_np = adap_np;
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of_changeset_init(&priv->chan[i].chgset);
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of_changeset_update_property(&priv->chan[i].chgset, adap_np, &status_okay);
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}
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priv->num_chan = num_chan;
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priv->dev = &pdev->dev;
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platform_set_drvdata(pdev, priv);
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/* switch to first parent as active master */
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i2c_demux_activate_master(priv, 0);
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err = device_create_file(&pdev->dev, &dev_attr_cur_master);
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if (err)
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goto err_rollback;
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return 0;
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err_rollback:
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for (j = 0; j < i; j++) {
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of_node_put(priv->chan[j].parent_np);
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of_changeset_destroy(&priv->chan[j].chgset);
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}
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return err;
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}
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static int i2c_demux_pinctrl_remove(struct platform_device *pdev)
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{
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struct i2c_demux_pinctrl_priv *priv = platform_get_drvdata(pdev);
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int i;
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device_remove_file(&pdev->dev, &dev_attr_cur_master);
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i2c_demux_deactivate_master(priv);
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for (i = 0; i < priv->num_chan; i++) {
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of_node_put(priv->chan[i].parent_np);
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of_changeset_destroy(&priv->chan[i].chgset);
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}
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return 0;
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}
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static const struct of_device_id i2c_demux_pinctrl_of_match[] = {
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{ .compatible = "i2c-demux-pinctrl", },
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{},
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};
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MODULE_DEVICE_TABLE(of, i2c_demux_pinctrl_of_match);
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static struct platform_driver i2c_demux_pinctrl_driver = {
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.driver = {
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.name = "i2c-demux-pinctrl",
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.of_match_table = i2c_demux_pinctrl_of_match,
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},
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.probe = i2c_demux_pinctrl_probe,
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.remove = i2c_demux_pinctrl_remove,
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};
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module_platform_driver(i2c_demux_pinctrl_driver);
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MODULE_DESCRIPTION("pinctrl-based I2C demux driver");
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MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
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MODULE_LICENSE("GPL v2");
|
||||
MODULE_ALIAS("platform:i2c-demux-pinctrl");
|
||||
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Reference in New Issue