i2c: muxes: add support for tsd,mule-i2c multiplexer

Theobroma Systems Mule is an MCU that emulates a set of I2C devices,
among which an amc6821 and devices that are reachable through an I2C-mux.
The devices on the mux can be selected by writing the appropriate device
number to an I2C config register (amc6821 reg 0xff).

This driver is expected to be probed as a platform device with amc6821
as its parent i2c device.

Add support for the mule-i2c-mux platform driver. The amc6821 driver
support for the mux will be added in a later commit.

Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Farouk Bouabid <farouk.bouabid@cherry.de>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index db1b9057612a54dc2d5b6e8106316773a21648e1..6d2f66810cdc57ce2b10054afb72bc2c6ff3471f 100644 (file)
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -119,4 +119,20 @@ config I2C_MUX_MLXCPLD
          This driver can also be built as a module.  If so, the module
          will be called i2c-mux-mlxcpld.
 
+config I2C_MUX_MULE
+       tristate "Theobroma Systems Mule I2C device multiplexer"
+       depends on OF && SENSORS_AMC6821
+       help
+         Mule is an MCU that emulates a set of I2C devices, among which
+         devices that are reachable through an I2C-mux. The devices on the mux
+         can be selected by writing the appropriate device number to an I2C
+         configuration register.
+
+         If you say yes to this option, support will be included for a
+         Theobroma Systems Mule I2C multiplexer. This driver provides access to
+         I2C devices connected on this mux.
+
+         This driver can also be built as a module.  If so, the module
+         will be called i2c-mux-mule.
+
 endmenu

diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
index 6d9d865e8518a27ab76ce96c44d7932e2e2ceee8..4b24f49515a798010e472986d1587e3e23c2437c 100644 (file)
--- a/drivers/i2c/muxes/Makefile
+++ b/drivers/i2c/muxes/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_I2C_MUX_GPIO)    += i2c-mux-gpio.o
 obj-$(CONFIG_I2C_MUX_GPMUX)    += i2c-mux-gpmux.o
 obj-$(CONFIG_I2C_MUX_LTC4306)  += i2c-mux-ltc4306.o
 obj-$(CONFIG_I2C_MUX_MLXCPLD)  += i2c-mux-mlxcpld.o
+obj-$(CONFIG_I2C_MUX_MULE)     += i2c-mux-mule.o
 obj-$(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-mule.c b/drivers/i2c/muxes/i2c-mux-mule.c
new file mode 100644 (file)
index 0000000..8e94247
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-mule.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Theobroma Systems Mule I2C device multiplexer
+ *
+ * Copyright (C) 2024 Theobroma Systems Design und Consulting GmbH
+ */
+
+#include <linux/i2c-mux.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+#define MULE_I2C_MUX_CONFIG_REG  0xff
+#define MULE_I2C_MUX_DEFAULT_DEV 0x0
+
+struct mule_i2c_reg_mux {
+       struct regmap *regmap;
+};
+
+static int mule_i2c_mux_select(struct i2c_mux_core *muxc, u32 dev)
+{
+       struct mule_i2c_reg_mux *mux = muxc->priv;
+
+       return regmap_write(mux->regmap, MULE_I2C_MUX_CONFIG_REG, dev);
+}
+
+static int mule_i2c_mux_deselect(struct i2c_mux_core *muxc, u32 dev)
+{
+       return mule_i2c_mux_select(muxc, MULE_I2C_MUX_DEFAULT_DEV);
+}
+
+static void mule_i2c_mux_remove(void *data)
+{
+       struct i2c_mux_core *muxc = data;
+
+       i2c_mux_del_adapters(muxc);
+
+       mule_i2c_mux_deselect(muxc, MULE_I2C_MUX_DEFAULT_DEV);
+}
+
+static int mule_i2c_mux_probe(struct platform_device *pdev)
+{
+       struct device *mux_dev = &pdev->dev;
+       struct mule_i2c_reg_mux *priv;
+       struct i2c_client *client;
+       struct i2c_mux_core *muxc;
+       struct device_node *dev;
+       unsigned int readback;
+       int ndev, ret;
+       bool old_fw;
+
+       /* Count devices on the mux */
+       ndev = of_get_child_count(mux_dev->of_node);
+       dev_dbg(mux_dev, "%d devices on the mux\n", ndev);
+
+       client = to_i2c_client(mux_dev->parent);
+
+       muxc = i2c_mux_alloc(client->adapter, mux_dev, ndev, sizeof(*priv),
+                            I2C_MUX_LOCKED, mule_i2c_mux_select, mule_i2c_mux_deselect);
+       if (!muxc)
+               return -ENOMEM;
+
+       priv = i2c_mux_priv(muxc);
+
+       priv->regmap = dev_get_regmap(mux_dev->parent, NULL);
+       if (IS_ERR(priv->regmap))
+               return dev_err_probe(mux_dev, PTR_ERR(priv->regmap),
+                                    "No parent i2c register map\n");
+
+       platform_set_drvdata(pdev, muxc);
+
+       /*
+        * MULE_I2C_MUX_DEFAULT_DEV is guaranteed to exist on all old and new
+        * mule fw. Mule fw without mux support will accept write ops to the
+        * config register, but readback returns 0xff (register not updated).
+        */
+       ret = mule_i2c_mux_select(muxc, MULE_I2C_MUX_DEFAULT_DEV);
+       if (ret)
+               return dev_err_probe(mux_dev, ret,
+                                    "Failed to write config register\n");
+
+       ret = regmap_read(priv->regmap, MULE_I2C_MUX_CONFIG_REG, &readback);
+       if (ret)
+               return dev_err_probe(mux_dev, ret,
+                                    "Failed to read config register\n");
+
+       old_fw = (readback != MULE_I2C_MUX_DEFAULT_DEV);
+
+       ret = devm_add_action_or_reset(mux_dev, mule_i2c_mux_remove, muxc);
+       if (ret)
+               return dev_err_probe(mux_dev, ret,
+                                    "Failed to register mux remove\n");
+
+       /* Create device adapters */
+       for_each_child_of_node(mux_dev->of_node, dev) {
+               u32 reg;
+
+               ret = of_property_read_u32(dev, "reg", &reg);
+               if (ret)
+                       return dev_err_probe(mux_dev, ret,
+                                            "No reg property found for %s\n",
+                                            of_node_full_name(dev));
+
+               if (old_fw && reg != 0) {
+                       dev_warn(mux_dev,
+                                "Mux is not supported, please update Mule FW\n");
+                       continue;
+               }
+
+               ret = mule_i2c_mux_select(muxc, reg);
+               if (ret) {
+                       dev_warn(mux_dev,
+                                "Device %d not supported, please update Mule FW\n", reg);
+                       continue;
+               }
+
+               ret = i2c_mux_add_adapter(muxc, 0, reg);
+               if (ret)
+                       return ret;
+       }
+
+       mule_i2c_mux_deselect(muxc, MULE_I2C_MUX_DEFAULT_DEV);
+
+       return 0;
+}
+
+static const struct of_device_id mule_i2c_mux_of_match[] = {
+       { .compatible = "tsd,mule-i2c-mux", },
+       {},
+};
+MODULE_DEVICE_TABLE(of, mule_i2c_mux_of_match);
+
+static struct platform_driver mule_i2c_mux_driver = {
+       .driver = {
+               .name   = "mule-i2c-mux",
+               .of_match_table = mule_i2c_mux_of_match,
+       },
+       .probe          = mule_i2c_mux_probe,
+};
+
+module_platform_driver(mule_i2c_mux_driver);
+
+MODULE_AUTHOR("Farouk Bouabid <farouk.bouabid@cherry.de>");
+MODULE_DESCRIPTION("I2C mux driver for Theobroma Systems Mule");
+MODULE_LICENSE("GPL");