Re: [PATCH 04/12] i3c: master: Support ACPI enumeration

[Frank Li <Frank.li@nxp.com>]

On Wed, Mar 18, 2026 at 10:57:17PM +0530, Akhil R wrote:
> Support ACPI enumeration for I2C and I3C devices on an I3C bus.
> Read _ADR and LVR from the ACPI resources and extract the data

ADR have _, but not _ before LVR, I am not familary with ACPI.

> as per the ACPI specification for an I3C bus. Also read
> mipi-i3c-static-address as per the MIPI DISCO specifications [1]
> to get the static address to be used.
>
> Although the existing subsystem allows host controllers to register
> through the ACPI table, it was not possible to describe I3C or I2C
> devices there.

why?

> This change enables describing the I3C or I2C devices

Don't use "This commit/change/" just Enable ...

Frank
> in the ACPI table, which is required if the device is using a static
> address or if it needs some specific properties to be attached to it.
>
> [1] https://www.mipi.org/specifications/disco
>
> Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
> ---
>  drivers/i3c/master.c | 101 +++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 93 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> index 2c479fecbfdf..15a356a2b3c8 100644
> --- a/drivers/i3c/master.c
> +++ b/drivers/i3c/master.c
> @@ -2404,12 +2404,31 @@ EXPORT_SYMBOL_GPL(i3c_master_add_i3c_dev_locked);
>
>  #define OF_I3C_REG1_IS_I2C_DEV			BIT(31)
>
> +static int i3c_acpi_get_i2c_resource(struct acpi_resource *ares, void *data)
> +{
> +	struct i2c_dev_boardinfo *boardinfo = data;
> +	struct acpi_resource_i2c_serialbus *sb;
> +
> +	if (!i2c_acpi_get_i2c_resource(ares, &sb))
> +		return 1;
> +
> +	boardinfo->base.addr = sb->slave_address;
> +	if (sb->access_mode == ACPI_I2C_10BIT_MODE)
> +		boardinfo->base.flags |= I2C_CLIENT_TEN;
> +
> +	boardinfo->lvr = sb->lvr;
> +
> +	return 0;
> +}
> +
>  static int
>  i3c_master_add_i2c_boardinfo(struct i3c_master_controller *master,
>  			     struct fwnode_handle *fwnode, u32 *reg)
>  {
>  	struct i2c_dev_boardinfo *boardinfo;
>  	struct device *dev = &master->dev;
> +	struct acpi_device *adev;
> +	LIST_HEAD(resources);
>  	int ret;
>
>  	boardinfo = devm_kzalloc(dev, sizeof(*boardinfo), GFP_KERNEL);
> @@ -2420,6 +2439,23 @@ i3c_master_add_i2c_boardinfo(struct i3c_master_controller *master,
>  		ret = of_i2c_get_board_info(dev, to_of_node(fwnode), &boardinfo->base);
>  		if (ret)
>  			return ret;
> +
> +		/* LVR is encoded in reg[2] for Device Tree. */
> +		boardinfo->lvr = reg[2];
> +	} else if (is_acpi_device_node(fwnode)) {
> +		adev = to_acpi_device_node(fwnode);
> +		boardinfo->base.fwnode = acpi_fwnode_handle(adev);
> +
> +		ret = acpi_dev_get_resources(adev, &resources,
> +					     i3c_acpi_get_i2c_resource, boardinfo);
> +
> +		if (ret < 0)
> +			return ret;
> +
> +		acpi_dev_free_resource_list(&resources);
> +
> +		if (!boardinfo->base.addr)
> +			return -ENODEV;
>  	} else {
>  		return -EINVAL;
>  	}
> @@ -2434,9 +2470,6 @@ i3c_master_add_i2c_boardinfo(struct i3c_master_controller *master,
>  		return -EOPNOTSUPP;
>  	}
>
> -	/* LVR is encoded in reg[2]. */
> -	boardinfo->lvr = reg[2];
> -
>  	list_add_tail(&boardinfo->node, &master->boardinfo.i2c);
>  	fwnode_handle_get(fwnode);
>
> @@ -2491,8 +2524,8 @@ i3c_master_add_i3c_boardinfo(struct i3c_master_controller *master,
>  	return 0;
>  }
>
> -static int i3c_master_add_dev(struct i3c_master_controller *master,
> -			      struct fwnode_handle *fwnode)
> +static int i3c_master_add_of_dev(struct i3c_master_controller *master,
> +				 struct fwnode_handle *fwnode)
>  {
>  	u32 reg[3];
>  	int ret;
> @@ -2516,6 +2549,31 @@ static int i3c_master_add_dev(struct i3c_master_controller *master,
>  	return ret;
>  }
>
> +static int i3c_master_add_acpi_dev(struct i3c_master_controller *master,
> +				   struct fwnode_handle *fwnode)
> +{
> +	struct acpi_device *adev = to_acpi_device_node(fwnode);
> +	acpi_bus_address adr;
> +	u32 reg[3] = { 0 };
> +
> +	/*
> +	 * If the ACPI table entry does not have _ADR method, it's an I2C device
> +	 * If the ACPI table entry has _ADR method, it's an I3C device
> +	 */
> +	if (!acpi_has_method(adev->handle, "_ADR"))
> +		return i3c_master_add_i2c_boardinfo(master, fwnode, reg);
> +
> +	adr = acpi_device_adr(adev);
> +
> +	/* For I3C devices, _ADR will have the 48 bit PID of the device  */
> +	reg[1] = upper_32_bits(adr);
> +	reg[2] = lower_32_bits(adr);
> +
> +	fwnode_property_read_u32(fwnode, "mipi-i3c-static-address", &reg[0]);
> +
> +	return i3c_master_add_i3c_boardinfo(master, fwnode, reg);
> +}
> +
>  static int fwnode_populate_i3c_bus(struct i3c_master_controller *master)
>  {
>  	struct device *dev = &master->dev;
> @@ -2527,7 +2585,13 @@ static int fwnode_populate_i3c_bus(struct i3c_master_controller *master)
>  		return 0;
>
>  	fwnode_for_each_available_child_node_scoped(fwnode, child) {
> -		ret = i3c_master_add_dev(master, child);
> +		if (is_of_node(child))
> +			ret = i3c_master_add_of_dev(master, child);
> +		else if (is_acpi_device_node(child))
> +			ret = i3c_master_add_acpi_dev(master, child);
> +		else
> +			continue;
> +
>  		if (ret)
>  			return ret;
>  	}
> @@ -2593,10 +2657,31 @@ static u8 i3c_master_i2c_get_lvr(struct i2c_client *client)
>  {
>  	/* Fall back to no spike filters and FM bus mode. */
>  	u8 lvr = I3C_LVR_I2C_INDEX(2) | I3C_LVR_I2C_FM_MODE;
> +	struct i2c_dev_boardinfo boardinfo;
> +	struct acpi_device *adev;
> +	LIST_HEAD(resources);
>  	u32 reg[3];
> +	int ret;
> +
> +	if (is_of_node(client->dev.fwnode)) {
> +		if (!fwnode_property_read_u32_array(client->dev.fwnode, "reg",
> +						    reg, ARRAY_SIZE(reg)))
> +			lvr = reg[2];
> +	} else if (is_acpi_device_node(client->dev.fwnode)) {
> +		adev = to_acpi_device_node(client->dev.fwnode);
> +		memset(&boardinfo, 0, sizeof(boardinfo));
> +
> +		ret = acpi_dev_get_resources(adev, &resources,
> +					     i3c_acpi_get_i2c_resource, &boardinfo);
>
> -	if (!fwnode_property_read_u32_array(client->dev.fwnode, "reg", reg, ARRAY_SIZE(reg)))
> -		lvr = reg[2];
> +		if (ret < 0)
> +			return lvr;
> +
> +		if (boardinfo.base.addr)
> +			lvr = boardinfo.lvr;
> +
> +		acpi_dev_free_resource_list(&resources);
> +	}
>
>  	return lvr;
>  }
> --
> 2.50.1
>