Re: [PATCH v3 3/7] i2c: muxes: add support for mule i2c multiplexer

[Farouk Bouabid <farouk.bouabid@cherry.de>]

Hi all,

On 11.06.24 13:43, Farouk Bouabid wrote:
> 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@cherry.de>
> ---
>   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", &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);


The class parameter was recently removed from this function but I forgot 
to remove it. Sorry for the noise, I will send a v4 for this fix.


Cheers,

Farouk


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