Re: [Patch v3] driver/i2c/mux: Add register-based mux i2c-mux-reg
From: Alexander Sverdlin
Date: Fri Jun 19 2015 - 02:28:30 EST
Hi!
On 18/06/15 21:57, ext York Sun wrote:
> Based on i2c-mux-gpio driver, similarly the register-based mux
> switch from one bus to another by setting a single register.
> The register can be on PCIe bus, local bus, or any memory-mapped
> address. The endianness of such register can be specified in device
> tree if used, or in platform data.
>
> Signed-off-by: York Sun <yorksun@xxxxxxxxxxxxx>
> CC: Wolfram Sang <wsa@xxxxxxxxxxxxx>
> CC: Paul Bolle <pebolle@xxxxxxxxxx>
> CC: Peter Korsgaard <peter.korsgaard@xxxxxxxxx>
> CC: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
I can think about external FPGA applications performing MUX function,
so the code looks useful to me.
Acked-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
> ---
> According to Alexander's feedback, readback is added. Different sizes
> are supported. I stick with iowrite but adding an option to use iowrite
> big endian in in case needed. Both big- and little-endian are tested.
> Comments are updated.
>
> Change log:
> v3: Add support of both big- and little-endian register
> Add readback after writing to register
> Add no-read option. By default, readback is alowed.
> Fix using chan_id transferred back from i2c-mux. It was mistakenly
> used as an index. It is actually the data to be written.
>
> v2: Update to GPLv2+ licence header
> Use iowrite instead of direct dereference the pointer to write register
> Add support of difference register size of 1/2/4 bytes
> Remove i2c_put_adapter(parent) in probe fucntion
> Replace multiple dev_info() with dev_dbg()
> Add idle_in_use variable to gate using idle value
> Add __iomem for register pointer
> Move platform data header file to include/linux/platform_data/
>
> .../devicetree/bindings/i2c/i2c-mux-reg.txt | 75 +++++
> drivers/i2c/muxes/Kconfig | 11 +
> drivers/i2c/muxes/Makefile | 1 +
> drivers/i2c/muxes/i2c-mux-reg.c | 299 ++++++++++++++++++++
> include/linux/platform_data/i2c-mux-reg.h | 44 +++
> 5 files changed, 430 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt
> create mode 100644 drivers/i2c/muxes/i2c-mux-reg.c
> create mode 100644 include/linux/platform_data/i2c-mux-reg.h
>
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt
> new file mode 100644
> index 0000000..6e3197f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i2c/i2c-mux-reg.txt
> @@ -0,0 +1,75 @@
> +Register-based I2C Bus Mux
> +
> +This binding describes an I2C bus multiplexer that uses a single register
> +to route the I2C signals.
> +
> +Required properties:
> +- compatible: i2c-mux-reg
> +- i2c-parent: The phandle of the I2C bus that this multiplexer's master-side
> + port is connected to.
> +* Standard I2C mux properties. See mux.txt in this directory.
> +* I2C child bus nodes. See mux.txt in this directory.
> +
> +Optional properties:
> +- reg: this pair of <offset size> specifies the register to control the mux.
> + The <offset size> depends on its parent node. It can be any memory-mapped
> + address. The size must be either 1, 2, or 4 bytes. If reg is omitted, the
> + resource of this device will be used.
> +- little-endian: The existence indicates the register is in little endian.
> + If omitted, the endianness of the host will be used.
> +- no-read: The existence indicates reading the register is not allowed.
> +- idle-state: value to set the muxer to when idle. When no value is
> + given, it defaults to the last value used.
> +
> +For each i2c child node, an I2C child bus will be created. They will
> +be numbered based on their order in the device tree.
> +
> +Whenever an access is made to a device on a child bus, the value set
> +in the revelant node's reg property will be output to the register.
> +
> +If an idle state is defined, using the idle-state (optional) property,
> +whenever an access is not being made to a device on a child bus, the
> +register will be set according to the idle value.
> +
> +If an idle state is not defined, the most recently used value will be
> +left programmed into the register.
> +
> +Example of a mux on PCIe card, the host is a powerpc SoC (big endian):
> +
> + i2c-mux {
> + /* the <offset size> depends on the address translation
> + * of the parent device. If omitted, device resource
> + * will be used instead. The size is to determine
> + * whether iowrite32, iowrite16, or iowrite8 will be used.
> + */
> + reg = <0x6028 0x4>;
> + little-endian; /* little endian register on PCIe */
> + compatible = "i2c-mux-reg";
> + #address-cells = <1>;
> + #size-cells = <0>;
> + i2c-parent = <&i2c1>;
> + i2c@0 {
> + reg = <0>;
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + si5338: clock-generator@70 {
> + compatible = "silabs,si5338";
> + reg = <0x70>;
> + /* other stuff */
> + };
> + };
> +
> + i2c@1 {
> + /* data is written using iowrite32 */
> + reg = <1>;
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + si5338: clock-generator@70 {
> + compatible = "silabs,si5338";
> + reg = <0x70>;
> + /* other stuff */
> + };
> + };
> + };
> diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
> index f6d313e..77c1257 100644
> --- a/drivers/i2c/muxes/Kconfig
> +++ b/drivers/i2c/muxes/Kconfig
> @@ -29,6 +29,17 @@ config I2C_MUX_GPIO
> This driver can also be built as a module. If so, the module
> will be called i2c-mux-gpio.
>
> +config I2C_MUX_REG
> + tristate "Register-based I2C multiplexer"
> + help
> + If you say yes to this option, support will be included for a
> + register based I2C multiplexer. This driver provides access to
> + I2C busses connected through a MUX, which is controlled
> + by a sinple register.
> +
> + This driver can also be built as a module. If so, the module
> + will be called i2c-mux-reg.
> +
> config I2C_MUX_PCA9541
> tristate "NXP PCA9541 I2C Master Selector"
> help
> diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
> index 465778b..bc517bb 100644
> --- a/drivers/i2c/muxes/Makefile
> +++ b/drivers/i2c/muxes/Makefile
> @@ -4,6 +4,7 @@
> obj-$(CONFIG_I2C_ARB_GPIO_CHALLENGE) += i2c-arb-gpio-challenge.o
>
> obj-$(CONFIG_I2C_MUX_GPIO) += i2c-mux-gpio.o
> +obj-$(CONFIG_I2C_MUX_REG) += i2c-mux-reg.o
> obj-$(CONFIG_I2C_MUX_PCA9541) += i2c-mux-pca9541.o
> obj-$(CONFIG_I2C_MUX_PCA954x) += i2c-mux-pca954x.o
> obj-$(CONFIG_I2C_MUX_PINCTRL) += i2c-mux-pinctrl.o
> diff --git a/drivers/i2c/muxes/i2c-mux-reg.c b/drivers/i2c/muxes/i2c-mux-reg.c
> new file mode 100644
> index 0000000..1692aec
> --- /dev/null
> +++ b/drivers/i2c/muxes/i2c-mux-reg.c
> @@ -0,0 +1,299 @@
> +/*
> + * I2C multiplexer using a single register
> + *
> + * Copyright 2015 Freescale Semiconductor
> + * York Sun <yorksun@xxxxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License as published by the
> + * Free Software Foundation; either version 2 of the License, or (at your
> + * option) any later version.
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/i2c-mux.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_data/i2c-mux-reg.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +
> +struct regmux {
> + struct i2c_adapter *parent;
> + struct i2c_adapter **adap; /* child busses */
> + struct i2c_mux_reg_platform_data data;
> +};
> +
> +static int i2c_mux_reg_set(const struct regmux *mux, unsigned int chan_id)
> +{
> + if (!mux->data.reg)
> + return -EINVAL;
> +
> + switch (mux->data.reg_size) {
> + case 4:
> + if (mux->data.little_endian) {
> + iowrite32(chan_id, mux->data.reg);
> + if (!mux->data.no_read)
> + ioread32(mux->data.reg);
> + } else {
> + iowrite32be(chan_id, mux->data.reg);
> + if (!mux->data.no_read)
> + ioread32(mux->data.reg);
> + }
> + break;
> + case 2:
> + if (mux->data.little_endian) {
> + iowrite16(chan_id, mux->data.reg);
> + if (!mux->data.no_read)
> + ioread16(mux->data.reg);
> + } else {
> + iowrite16be(chan_id, mux->data.reg);
> + if (!mux->data.no_read)
> + ioread16be(mux->data.reg);
> + }
> + break;
> + case 1:
> + iowrite8(chan_id, mux->data.reg);
> + if (!mux->data.no_read)
> + ioread8(mux->data.reg);
> + break;
> + default:
> + pr_err("Invalid register size\n");
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int i2c_mux_reg_select(struct i2c_adapter *adap, void *data,
> + unsigned int chan)
> +{
> + struct regmux *mux = data;
> +
> + return i2c_mux_reg_set(mux, chan);
> +}
> +
> +static int i2c_mux_reg_deselect(struct i2c_adapter *adap, void *data,
> + unsigned int chan)
> +{
> + struct regmux *mux = data;
> +
> + if (mux->data.idle_in_use)
> + return i2c_mux_reg_set(mux, mux->data.idle);
> +
> + return 0;
> +}
> +
> +#ifdef CONFIG_OF
> +static int i2c_mux_reg_probe_dt(struct regmux *mux,
> + struct platform_device *pdev)
> +{
> + struct device_node *np = pdev->dev.of_node;
> + struct device_node *adapter_np, *child;
> + struct i2c_adapter *adapter;
> + struct resource res;
> + unsigned *values;
> + int i = 0;
> +
> + if (!np)
> + return -ENODEV;
> +
> + adapter_np = of_parse_phandle(np, "i2c-parent", 0);
> + if (!adapter_np) {
> + dev_err(&pdev->dev, "Cannot parse i2c-parent\n");
> + return -ENODEV;
> + }
> + adapter = of_find_i2c_adapter_by_node(adapter_np);
> + if (!adapter) {
> + dev_err(&pdev->dev, "Cannot find parent bus\n");
> + return -EPROBE_DEFER;
> + }
> + mux->parent = adapter;
> + mux->data.parent = i2c_adapter_id(adapter);
> + put_device(&adapter->dev);
> +
> + mux->data.n_values = of_get_child_count(np);
> + if (of_find_property(np, "little-endian", NULL)) {
> + mux->data.little_endian = true;
> + } else {
> +#ifdef __LITTLE_ENDIAN__
> + mux->data.little_endian = true;
> +#elif defined(__BIG_ENDIAN__)
> + mux->data.little_endian = false;
> +#else
> +#error Endianness not defined?
> +#endif
> + }
> + if (of_find_property(np, "no-read", NULL))
> + mux->data.no_read = true;
> + else
> + mux->data.no_read = false;
> +
> + values = devm_kzalloc(&pdev->dev,
> + sizeof(*mux->data.values) * mux->data.n_values,
> + GFP_KERNEL);
> + if (!values) {
> + dev_err(&pdev->dev, "Cannot allocate values array");
> + return -ENOMEM;
> + }
> +
> + for_each_child_of_node(np, child) {
> + of_property_read_u32(child, "reg", values + i);
> + i++;
> + }
> + mux->data.values = values;
> +
> + if (!of_property_read_u32(np, "idle-state", &mux->data.idle))
> + mux->data.idle_in_use = true;
> +
> + /* map address from "reg" if exists */
> + if (of_address_to_resource(np, 0, &res)) {
> + mux->data.reg_size = resource_size(&res);
> + if (mux->data.reg_size > 4) {
> + dev_err(&pdev->dev, "Invalid address size\n");
> + return -EINVAL;
> + }
> + mux->data.reg = devm_ioremap_resource(&pdev->dev, &res);
> + if (IS_ERR(mux->data.reg))
> + return PTR_ERR(mux->data.reg);
> + }
> +
> + return 0;
> +}
> +#else
> +static int i2c_mux_reg_probe_dt(struct gpiomux *mux,
> + struct platform_device *pdev)
> +{
> + return 0;
> +}
> +#endif
> +
> +static int i2c_mux_reg_probe(struct platform_device *pdev)
> +{
> + struct regmux *mux;
> + struct i2c_adapter *parent;
> + struct resource *res;
> + int (*deselect)(struct i2c_adapter *, void *, u32);
> + unsigned int initial_state, class;
> + int i, ret, nr;
> +
> + mux = devm_kzalloc(&pdev->dev, sizeof(*mux), GFP_KERNEL);
> + if (!mux)
> + return -ENOMEM;
> +
> + platform_set_drvdata(pdev, mux);
> +
> + if (dev_get_platdata(&pdev->dev)) {
> + memcpy(&mux->data, dev_get_platdata(&pdev->dev),
> + sizeof(mux->data));
> +
> + parent = i2c_get_adapter(mux->data.parent);
> + if (!parent) {
> + dev_err(&pdev->dev, "Parent adapter (%d) not found\n",
> + mux->data.parent);
> + return -EPROBE_DEFER;
> + }
> + mux->parent = parent;
> + } else {
> + ret = i2c_mux_reg_probe_dt(mux, pdev);
> + if (ret < 0) {
> + dev_err(&pdev->dev, "Error parsing device tree");
> + return ret;
> + }
> + }
> +
> + if (!mux->data.reg) {
> + dev_info(&pdev->dev,
> + "Register not set, using platform resource\n");
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + mux->data.reg_size = resource_size(res);
> + if (mux->data.reg_size > 4) {
> + dev_err(&pdev->dev, "Invalid resource size\n");
> + return -EINVAL;
> + }
> + mux->data.reg = devm_ioremap_resource(&pdev->dev, res);
> + if (IS_ERR(mux->data.reg))
> + return PTR_ERR(mux->data.reg);
> + }
> +
> + mux->adap = devm_kzalloc(&pdev->dev,
> + sizeof(*mux->adap) * mux->data.n_values,
> + GFP_KERNEL);
> + if (!mux->adap) {
> + dev_err(&pdev->dev, "Cannot allocate i2c_adapter structure");
> + return -ENOMEM;
> + }
> +
> + if (mux->data.idle_in_use) {
> + initial_state = mux->data.idle;
> + deselect = i2c_mux_reg_deselect;
> + } else {
> + initial_state = mux->data.values[0];
> + deselect = NULL;
> + }
> +
> + for (i = 0; i < mux->data.n_values; i++) {
> + nr = mux->data.base_nr ? (mux->data.base_nr + i) : 0;
> + class = mux->data.classes ? mux->data.classes[i] : 0;
> +
> + mux->adap[i] = i2c_add_mux_adapter(mux->parent, &pdev->dev, mux,
> + nr, mux->data.values[i],
> + class, i2c_mux_reg_select,
> + deselect);
> + if (!mux->adap[i]) {
> + ret = -ENODEV;
> + dev_err(&pdev->dev, "Failed to add adapter %d\n", i);
> + goto add_adapter_failed;
> + }
> + }
> +
> + dev_dbg(&pdev->dev, "%d port mux on %s adapter\n",
> + mux->data.n_values, mux->parent->name);
> +
> + return 0;
> +
> +add_adapter_failed:
> + for (; i > 0; i--)
> + i2c_del_mux_adapter(mux->adap[i - 1]);
> +
> + return ret;
> +}
> +
> +static int i2c_mux_reg_remove(struct platform_device *pdev)
> +{
> + struct regmux *mux = platform_get_drvdata(pdev);
> + int i;
> +
> + for (i = 0; i < mux->data.n_values; i++)
> + i2c_del_mux_adapter(mux->adap[i]);
> +
> + i2c_put_adapter(mux->parent);
> +
> + dev_dbg(&pdev->dev, "Removed\n");
> +
> + return 0;
> +}
> +
> +static const struct of_device_id i2c_mux_reg_of_match[] = {
> + { .compatible = "i2c-mux-reg", },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, i2c_mux_reg_of_match);
> +
> +static struct platform_driver i2c_mux_reg_driver = {
> + .probe = i2c_mux_reg_probe,
> + .remove = i2c_mux_reg_remove,
> + .driver = {
> + .owner = THIS_MODULE,
> + .name = "i2c-mux-reg",
> + },
> +};
> +
> +module_platform_driver(i2c_mux_reg_driver);
> +
> +MODULE_DESCRIPTION("Register-based I2C multiplexer driver");
> +MODULE_AUTHOR("York Sun <yorksun@xxxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:i2c-mux-reg");
> diff --git a/include/linux/platform_data/i2c-mux-reg.h b/include/linux/platform_data/i2c-mux-reg.h
> new file mode 100644
> index 0000000..cf0cc1e
> --- /dev/null
> +++ b/include/linux/platform_data/i2c-mux-reg.h
> @@ -0,0 +1,44 @@
> +/*
> + * I2C multiplexer using a single register
> + *
> + * Copyright 2015 Freescale Semiconductor
> + * York Sun <yorksun@xxxxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License as published by the
> + * Free Software Foundation; either version 2 of the License, or (at your
> + * option) any later version.
> + */
> +
> +#ifndef __LINUX_PLATFORM_DATA_I2C_MUX_REG_H
> +#define __LINUX_PLATFORM_DATA_I2C_MUX_REG_H
> +
> +/**
> + * struct i2c_mux_reg_platform_data - Platform-dependent data for i2c-mux-reg
> + * @parent: Parent I2C bus adapter number
> + * @base_nr: Base I2C bus number to number adapters from or zero for dynamic
> + * @values: Array of value for each channel
> + * @n_values: Number of multiplexer channels
> + * @little_endian: Indicating if the register is in little endian
> + * @no_read: Reading the register is not allowed by hardware
> + * @classes: Optional I2C auto-detection classes
> + * @idle: Value to write to mux when idle
> + * @idle_in_use: indicate if idle value is in use
> + * @reg: Virtual address of the register to switch channel
> + * @reg_size: register size in bytes
> + */
> +struct i2c_mux_reg_platform_data {
> + int parent;
> + int base_nr;
> + const unsigned int *values;
> + int n_values;
> + bool little_endian;
> + bool no_read;
> + const unsigned int *classes;
> + u32 idle;
> + bool idle_in_use;
> + void __iomem *reg;
> + resource_size_t reg_size;
> +};
> +
> +#endif /* __LINUX_PLATFORM_DATA_I2C_MUX_REG_H */
--
Best regards,
Alexander Sverdlin.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/