Mule is an MCU that emulates a set of I2C devices which are reachable
through an I2C-mux.
The emulated devices share a single I2C address with the mux itself
where the requested register is what determines which logic is executed
(mux logic or device logic):
1- The devices on the mux can be selected (mux function) by writing the
appropriate device number to an I2C config register (0xff) that is not
used by any device logic.
2- Any access to a register other than the config register will be
handled by the previously selected device.
Signed-off-by: Farouk Bouabid <farouk.bouabid@xxxxxxxxx>
---
drivers/i2c/muxes/Kconfig | 18 +++++
drivers/i2c/muxes/Makefile | 1 +
drivers/i2c/muxes/i2c-mux-mule.c | 157 +++++++++++++++++++++++++++++++++++++++
3 files changed, 176 insertions(+)
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index db1b9057612a..70876259796d 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -119,4 +119,22 @@ 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 "Mule I2C device multiplexer"
+ depends on OF
+ help
+ Mule is an MCU that emulates a set of I2C devices which are reachable
+ through an I2C-mux.
+
+ The emulated devices share a single I2C address with the mux itself
+ where the requested register is what determines which logic is executed
+ (mux logic or device logic).
+
+ If you say yes to this option, support will be included for a
+ Mule I2C device multiplexer. This driver provides access to
+ I2C devices connected on the Mule I2C 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 6d9d865e8518..4b24f49515a7 100644
--- 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
index 000000000000..db27fa560995
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-mule.c
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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/property.h>
+#include <linux/regmap.h>
+
+#define MUX_CONFIG_REG 0xff
+#define MUX_DEFAULT_DEV 0x0
+
+struct mule_i2c_reg_mux {
+ struct regmap *regmap;
+};
+
+static const struct regmap_config mule_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+};
+
+static inline int __mux_select(struct regmap *regmap, u32 dev)
+{
+ return regmap_write(regmap, MUX_CONFIG_REG, dev);
+}
+
+static int mux_select(struct i2c_mux_core *muxc, u32 dev)
+{
+ struct mule_i2c_reg_mux *mux = muxc->priv;
+
+ return __mux_select(mux->regmap, dev);
+}
+
+static int mux_deselect(struct i2c_mux_core *muxc, u32 dev)
+{
+ return mux_select(muxc, MUX_DEFAULT_DEV);
+}
+
+static void mux_remove(void *data)
+{
+ struct i2c_mux_core *muxc = data;
+
+ i2c_mux_del_adapters(muxc);
+
+ mux_deselect(muxc, MUX_DEFAULT_DEV);
+}
+
+static int mule_i2c_mux_probe(struct i2c_client *client)
+{
+ struct i2c_adapter *adap = client->adapter;
+ struct mule_i2c_reg_mux *priv;
+ 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(client->dev.of_node);
+ dev_dbg(&client->dev, "%u devices on the mux\n", ndev);
+
+ muxc = i2c_mux_alloc(adap, &client->dev,
+ ndev, sizeof(*priv),
+ I2C_MUX_LOCKED,
+ mux_select, mux_deselect);
+ if (!muxc)
+ return -ENOMEM;
+
+ muxc->share_addr_with_children = 1;
+ priv = i2c_mux_priv(muxc);
+
+ priv->regmap = devm_regmap_init_i2c(client, &mule_regmap_config);
+ if (IS_ERR(priv->regmap))
+ return dev_err_probe(&client->dev, PTR_ERR(priv->regmap),
+ "Failed to allocate i2c register map\n");
+
+ i2c_set_clientdata(client, muxc);
+
+ /*
+ * Mux 0 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 = mux_select(muxc, 0);
+ if (ret)
+ return ret;
+
+ ret = regmap_read(priv->regmap, MUX_CONFIG_REG, &readback);
+ if (ret)
+ return ret;
+
+ old_fw = (readback != 0);
+
+ ret = devm_add_action_or_reset(&client->dev, mux_remove, muxc);
+ if (ret)
+ return ret;
+
+ /* Create device adapters */
+ for_each_child_of_node(client->dev.of_node, dev) {
+ u32 reg;
+
+ ret = of_property_read_u32(dev, "reg", ®);
+ if (ret) {
+ dev_err(&client->dev, "No reg property found for %s: %d\n",
+ of_node_full_name(dev), ret);
+ return ret;
+ }
+
+ if (old_fw && reg != 0) {
+ dev_warn(&client->dev,
+ "Mux %d not supported, please update Mule FW\n", reg);
+ continue;
+ }
+
+ ret = mux_select(muxc, reg);
+ if (ret) {
+ dev_warn(&client->dev,
+ "Mux %d not supported, please update Mule FW\n", reg);
+ continue;
+ }
+
+ ret = i2c_mux_add_adapter(muxc, 0, reg, 0);
