From: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxx>
---
.../devicetree/bindings/i2c/i2c-demux-pinctrl.txt | 44 ++++
drivers/i2c/muxes/Kconfig | 9 +
drivers/i2c/muxes/Makefile | 2 +
drivers/i2c/muxes/i2c-demux-pinctrl.c | 266 +++++++++++++++++++++
4 files changed, 321 insertions(+)
create mode 100644 Documentation/devicetree/bindings/i2c/i2c-demux-pinctrl.txt
create mode 100644 drivers/i2c/muxes/i2c-demux-pinctrl.c
diff --git a/Documentation/devicetree/bindings/i2c/i2c-demux-pinctrl.txt b/Documentation/devicetree/bindings/i2c/i2c-demux-pinctrl.txt
new file mode 100644
index 00000000000000..2211f6acbf8c0c
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/i2c-demux-pinctrl.txt
@@ -0,0 +1,44 @@
+Pinctrl-based I2C Bus DeMux
+
+This binding describes an I2C bus demultiplexer that uses pin multiplexing to
+route the I2C signals, and represents the pin multiplexing configuration using
+the pinctrl device tree bindings. This may be used to select one I2C IP core at
+runtime which may have a better feature set for a given task than another I2C
+IP core on the SoC.
+
+ +------------------------------+
+ | SoC |
+ | | +-----+ +-----+
+ | +------------+ | | dev | | dev |
+ | |I2C IP Core1|--\ | +-----+ +-----+
+ | +------------+ \------+ | | |
+ | |Pinmux|--|------+--------+
+ | +------------+ +------+ |
+ | |I2C IP Core2|--/ |
+ | +------------+ |
+ | |
+ +------------------------------+
+
+Required properties:
+- compatible: "i2c-demux-pinctrl"
+- i2c-parent: List of phandles of I2C cores to be selected
+- i2c-bus-name: the name of this bus
+
+Also I2C mux properties and child nodes. See mux.txt in this directory.
+
+Also required:
+
+- pinctrl properties for the parent I2C controllers need a pinctrl state
+ with the same name as i2c-bus-name, not "default"!
+
+- the i2c masters must have their status "disabled". This driver will
+ enable them at runtime when needed.
+
+//FIXME: add example
+
+Changing I2C controllers:
+
+The created mux-device will have a file "cur_master" in its sysfs-entry. Write
+0 there for the first master listed in the "i2c-parent" property, 1 for the
+second etc. Reading the file will give you a list with the active master
+marked.
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index f6d313e528de34..b99cc15d683a50 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -60,4 +60,13 @@ config I2C_MUX_PINCTRL
This driver can also be built as a module. If so, the module will be
called pinctrl-i2cmux.
+config I2C_DEMUX_PINCTRL
+ tristate "pinctrl-based I2C demultiplexer"
+ depends on PINCTRL
+ select OF_DYNAMIC
+ help
+ If you say yes to this option, support will be included for an I2C
+ demultiplexer that uses the pinctrl subsystem. This is useful if you
+ want to change the I2C master at run-time depending on features.
+
endmenu
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 465778b5d5dc86..4d14cb88d83438 100644
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -3,6 +3,8 @@
obj-$(CONFIG_I2C_ARB_GPIO_CHALLENGE) += i2c-arb-gpio-challenge.o
+obj-$(CONFIG_I2C_DEMUX_PINCTRL) += i2c-demux-pinctrl.o
+
obj-$(CONFIG_I2C_MUX_GPIO) += i2c-mux-gpio.o
obj-$(CONFIG_I2C_MUX_PCA9541) += i2c-mux-pca9541.o
obj-$(CONFIG_I2C_MUX_PCA954x) += i2c-mux-pca954x.o
diff --git a/drivers/i2c/muxes/i2c-demux-pinctrl.c b/drivers/i2c/muxes/i2c-demux-pinctrl.c
new file mode 100644
index 00000000000000..5444c65de76c55
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-demux-pinctrl.c
@@ -0,0 +1,266 @@
+/*
+ * Pinctrl based I2C DeMultiplexer V2 PROTOTYPE!
+ *
+ * Copyright (C) 2015 by Wolfram Sang, Sang Engineering <wsa@xxxxxxxxxxxxxxxxxxxx>
+ * Copyright (C) 2015 by Renesas Electronics Corporation
+ *
+ * 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; version 2 of the License.
+ *
+ * See the bindings doc for DTS setup.
+ */
+
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/pinctrl/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+struct i2c_demux_pinctrl_chan {
+ struct device_node *parent_np;
+ struct i2c_adapter *parent_adap;
+ struct of_changeset chgset;
+};
+
+struct i2c_demux_pinctrl_priv {
+ int cur_chan;
+ int num_chan;
+ struct device *dev;
+ const char *bus_name;
+ struct i2c_adapter cur_adap;
+ struct i2c_algorithm algo;
+ struct i2c_demux_pinctrl_chan chan[];
+};
+
+static struct property status_okay = { .name = "status", .length = 3, .value = "ok" };
+
+static int i2c_demux_master_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
+{
+ struct i2c_demux_pinctrl_priv *priv = adap->algo_data;
+ struct i2c_adapter *parent = priv->chan[priv->cur_chan].parent_adap;
+
+ return __i2c_transfer(parent, msgs, num);
+}
+
+static u32 i2c_demux_functionality(struct i2c_adapter *adap)
+{
+ struct i2c_demux_pinctrl_priv *priv = adap->algo_data;
+ struct i2c_adapter *parent = priv->chan[priv->cur_chan].parent_adap;
+
+ return parent->algo->functionality(parent);
+}
+
+static int i2c_demux_activate_master(struct i2c_demux_pinctrl_priv *priv, u32 new_chan)
+{
+ struct i2c_adapter *adap;
+ struct pinctrl *p;
+ int ret;
+
+ mutex_lock(&of_mutex);
+ ret = of_changeset_apply(&priv->chan[new_chan].chgset);
+ mutex_unlock(&of_mutex);
+ if (ret)
+ return ret;
+
+ adap = of_find_i2c_adapter_by_node(priv->chan[new_chan].parent_np);
+ if (!adap)
+ return -EPROBE_DEFER;
+
+ p = devm_pinctrl_get_select(adap->dev.parent, priv->bus_name);
+ if (IS_ERR(p)) {
+ put_device(&adap->dev);
+ return PTR_ERR(p);
+ }
+
+ priv->chan[new_chan].parent_adap = adap;
+ priv->cur_chan = new_chan;
+
+ /* Now fill out current adapter structure. cur_chan must be up to date */
+ priv->algo.master_xfer = i2c_demux_master_xfer;
+ priv->algo.functionality = i2c_demux_functionality;
+
+ snprintf(priv->cur_adap.name, sizeof(priv->cur_adap.name),
+ "i2c-demux (master i2c-%d)", i2c_adapter_id(adap));
+ priv->cur_adap.owner = THIS_MODULE;
+ priv->cur_adap.algo = &priv->algo;
+ priv->cur_adap.algo_data = priv;
+ priv->cur_adap.dev.parent = priv->dev;
+ priv->cur_adap.class = adap->class;
+ priv->cur_adap.retries = adap->retries;
+ priv->cur_adap.timeout = adap->timeout;
+ priv->cur_adap.quirks = adap->quirks;
+ priv->cur_adap.dev.of_node = priv->dev->of_node;
+ ret = i2c_add_adapter(&priv->cur_adap);
+ if (ret < 0) {
+ dev_err(priv->dev, "failed to add demux-adapter (%d)\n", ret);
+ priv->cur_chan = -EINVAL;
+ return ret;
+ }
+
+ return 0;
+}
+
+static int i2c_demux_deactivate_master(struct i2c_demux_pinctrl_priv *priv)
+{
+ int ret;
+
+ i2c_del_adapter(&priv->cur_adap);
+ put_device(&priv->chan[priv->cur_chan].parent_adap->dev);
+
+ mutex_lock(&of_mutex);
+ ret = of_changeset_revert(&priv->chan[priv->cur_chan].chgset);
+ mutex_unlock(&of_mutex);
+
+ return ret;
+}
+
+static int i2c_demux_change_master(struct i2c_demux_pinctrl_priv *priv, u32 new_chan)
+{
+ int ret;
+
+ if (new_chan == priv->cur_chan)
+ return 0;
+
+ ret = i2c_demux_deactivate_master(priv);
+ if (ret)
+ return ret;
+
+ return i2c_demux_activate_master(priv, new_chan);
+}
+
+static ssize_t cur_master_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct i2c_demux_pinctrl_priv *priv = dev_get_drvdata(dev);
+ int count = 0, i;
+
+ for (i = 0; i < priv->num_chan; i++)
+ count += sprintf(buf + count, "%c %d - %s\n",
+ i == priv->cur_chan ? '*' : ' ', i,
+ priv->chan[i].parent_np->full_name);
+ //FIXME: Check count > PAGE_SIZE
+
+ return count;
+}
+
+static ssize_t cur_master_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct i2c_demux_pinctrl_priv *priv = dev_get_drvdata(dev);
+ unsigned long val;
+ int ret;
+
+ ret = kstrtoul(buf, 0, &val);
+ if (ret < 0)
+ return ret;
+
+ if (val >= priv->num_chan)
+ return -EINVAL;
+
+ ret = i2c_demux_change_master(priv, val);
+
+ return ret < 0 ? ret : count;
+}
+static DEVICE_ATTR_RW(cur_master);
+
+static int i2c_demux_pinctrl_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct i2c_demux_pinctrl_priv *priv;
+ int num_chan, i, j, err;
+
+ num_chan = of_count_phandle_with_args(np, "i2c-parent", NULL);
+ if (num_chan < 2) {
+ dev_err(&pdev->dev, "Need at least two I2C masters to switch\n");
+ return -EINVAL;
+ }
+
+ priv = devm_kzalloc(&pdev->dev, sizeof(*priv)
+ + num_chan * sizeof(struct i2c_demux_pinctrl_chan), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ err = of_property_read_string(np, "i2c-bus-name", &priv->bus_name);
+ if (err)
+ return err;
+
+ for (i = 0; i < num_chan; i++) {
+ struct device_node *adap_np;
+
+ adap_np = of_parse_phandle(np, "i2c-parent", i);
+ if (!adap_np) {
+ dev_err(&pdev->dev, "can't get phandle for parent %d\n", i);
+ err = -ENOENT;
+ goto err_rollback;
+ }
+ priv->chan[i].parent_np = adap_np;
+
+ of_changeset_init(&priv->chan[i].chgset);
+ of_changeset_update_property(&priv->chan[i].chgset, adap_np, &status_okay);
+ }
+
+ priv->num_chan = num_chan;
+ priv->dev = &pdev->dev;
+
+ platform_set_drvdata(pdev, priv);
+
+ /* switch to first parent as active master */
+ i2c_demux_activate_master(priv, 0);
+
+ err = device_create_file(&pdev->dev, &dev_attr_cur_master);
+ if (err)
+ goto err_rollback;
+
+ return 0;
+
+err_rollback:
+ for (j = 0; j < i; j++) {
+ of_node_put(priv->chan[j].parent_np);
+ of_changeset_destroy(&priv->chan[j].chgset);
+ }
+
+ return err;
+}
+
+static int i2c_demux_pinctrl_remove(struct platform_device *pdev)
+{
+ struct i2c_demux_pinctrl_priv *priv = platform_get_drvdata(pdev);
+ int i;
+
+ device_remove_file(&pdev->dev, &dev_attr_cur_master);
+
+ i2c_demux_deactivate_master(priv);
+
+ for (i = 0; i < priv->num_chan; i++) {
+ of_node_put(priv->chan[i].parent_np);
+ of_changeset_destroy(&priv->chan[i].chgset);
+ }
+
+ return 0;
+}
+
+static const struct of_device_id i2c_demux_pinctrl_of_match[] = {
+ { .compatible = "i2c-demux-pinctrl", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, i2c_demux_pinctrl_of_match);
+
+static struct platform_driver i2c_demux_pinctrl_driver = {
+ .driver = {
+ .name = "i2c-demux-pinctrl",
+ .of_match_table = i2c_demux_pinctrl_of_match,
+ },
+ .probe = i2c_demux_pinctrl_probe,
+ .remove = i2c_demux_pinctrl_remove,
+};
+module_platform_driver(i2c_demux_pinctrl_driver);
+
+MODULE_DESCRIPTION("pinctrl-based I2C demux driver");
+MODULE_AUTHOR("Wolfram Sang <wsa@xxxxxxxxxxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:i2c-demux-pinctrl");
--
2.1.4
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