Re: [PATCH v3 1/1] i2c: add ACPI support for I2C mux ports

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

+Cc: Ismo Puustinen

On Mon, 2015-10-19 at 15:29 -0700, Dustin Byford wrote:
> Although I2C mux devices are easily enumerated using ACPI (_HID/_CID
> or
> device property compatible string match) enumerating I2C client
> devices
> connected through a I2C mux device requires a little extra work.
> 
> This change implements a method for describing an I2C device
> hierarchy that
> includes mux devices by using an ACPI Device() for each mux channel
> along
> with an _ADR to set the channel number for the device.  See
> Documentation/acpi/i2c-muxes.txt for a simple example.

Ismo, can you test this patch on top of what you have to see if it goes
smoothly (no break of Galileo Gen2 support) ?

> 
> Signed-off-by: Dustin Byford <dustin@cumulusnetworks.com>
> ---
>  Documentation/acpi/i2c-muxes.txt | 58
> ++++++++++++++++++++++++++++++++++++++++
>  drivers/i2c/i2c-core.c           | 15 +++++++++--
>  drivers/i2c/i2c-mux.c            |  8 ++++++
>  include/linux/acpi.h             |  6 +++++
>  4 files changed, 85 insertions(+), 2 deletions(-)
>  create mode 100644 Documentation/acpi/i2c-muxes.txt
> 
> diff --git a/Documentation/acpi/i2c-muxes.txt
> b/Documentation/acpi/i2c-muxes.txt
> new file mode 100644
> index 0000000..9fcc4f0
> --- /dev/null
> +++ b/Documentation/acpi/i2c-muxes.txt
> @@ -0,0 +1,58 @@
> +ACPI I2C Muxes
> +--------------
> +
> +Describing an I2C device hierarchy that includes I2C muxes requires
> an ACPI
> +Device () scope per mux channel.
> +
> +Consider this topology:
> +
> ++------+   +------+
> +| SMB1 |-->| MUX0 |--CH00--> i2c client A (0x50)
> +|      |   | 0x70 |--CH01--> i2c client B (0x50)
> ++------+   +------+
> +
> +which corresponds to the following ASL:
> +
> +Device (SMB1)
> +{
> +    Name (_HID, ...)
> +    Device (MUX0)
> +    {
> +        Name (_HID, ...)
> +        Name (_CRS, ResourceTemplate () {
> +            I2cSerialBus (0x70, ControllerInitiated, I2C_SPEED,
> +                          AddressingMode7Bit, "^SMB1", 0x00,
> +                          ResourceConsumer,,)
> +        }
> +
> +        Device (CH00)
> +        {
> +            Name (_ADR, 0)
> +
> +            Device (CLIA)
> +            {
> +                Name (_HID, ...)
> +                Name (_CRS, ResourceTemplate () {
> +                    I2cSerialBus (0x50, ControllerInitiated,
> I2C_SPEED,
> +                                  AddressingMode7Bit, "^CH00", 0x00,
> +                                  ResourceConsumer,,)
> +                }
> +            }
> +        }
> +
> +        Device (CH01)
> +        {
> +            Name (_ADR, 1)
> +
> +            Device (CLIB)
> +            {
> +                Name (_HID, ...)
> +                Name (_CRS, ResourceTemplate () {
> +                    I2cSerialBus (0x50, ControllerInitiated,
> I2C_SPEED,
> +                                  AddressingMode7Bit, "^CH01", 0x00,
> +                                  ResourceConsumer,,)
> +                }
> +            }
> +        }
> +    }
> +}
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 579b99d..af0811c 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -156,7 +156,7 @@ static acpi_status
> acpi_i2c_add_device(acpi_handle handle, u32 level,
>  	info.fwnode = acpi_fwnode_handle(adev);
>  
>  	memset(&lookup, 0, sizeof(lookup));
> -	lookup.adapter_handle = ACPI_HANDLE(adapter->dev.parent);
> +	lookup.adapter_handle = ACPI_HANDLE(&adapter->dev);
>  	lookup.device_handle = handle;
>  	lookup.info = &info;
>  
> @@ -212,7 +212,7 @@ static void acpi_i2c_register_devices(struct
> i2c_adapter *adap)
>  {
>  	acpi_status status;
>  
> -	if (!adap->dev.parent || !has_acpi_companion(adap-
> >dev.parent))
> +	if (!has_acpi_companion(&adap->dev))
>  		return;
>  
>  	status = acpi_walk_namespace(ACPI_TYPE_DEVICE,
> ACPI_ROOT_OBJECT,
> @@ -1667,6 +1667,17 @@ int i2c_add_adapter(struct i2c_adapter
> *adapter)
>  	struct device *dev = &adapter->dev;
>  	int id;
>  
> +	/*
> +	 * By default, associate I2C adapters with their parent
> device's ACPI
> +	 * node.
> +	 */
> +	if (!has_acpi_companion(dev)) {
> +		struct acpi_device *adev = ACPI_COMPANION(dev-
> >parent);
> +
> +		if (adev)
> +			ACPI_COMPANION_SET(dev, adev);
> +	}
> +
>  	if (dev->of_node) {
>  		id = of_alias_get_id(dev->of_node, "i2c");
>  		if (id >= 0) {
> diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
> index 2ba7c0f..00fc5b1 100644
> --- a/drivers/i2c/i2c-mux.c
> +++ b/drivers/i2c/i2c-mux.c
> @@ -25,6 +25,7 @@
>  #include <linux/i2c.h>
>  #include <linux/i2c-mux.h>
>  #include <linux/of.h>
> +#include <linux/acpi.h>
>  
>  /* multiplexer per channel data */
>  struct i2c_mux_priv {
> @@ -173,6 +174,13 @@ struct i2c_adapter *i2c_add_mux_adapter(struct
> i2c_adapter *parent,
>  		}
>  	}
>  
> +	/*
> +	 * Associate the mux channel with an ACPI node.
> +	 */
> +	if (has_acpi_companion(mux_dev))
> +		acpi_preset_companion(&priv->adap.dev,
> ACPI_COMPANION(mux_dev),
> +				      chan_id);
> +
>  	if (force_nr) {
>  		priv->adap.nr = force_nr;
>  		ret = i2c_add_numbered_adapter(&priv->adap);
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 51a96a8..66564f8 100644



> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -505,6 +505,12 @@ static inline bool has_acpi_companion(struct
> device *dev)
>  	return false;
>  }
>  
> +static inline void acpi_preset_companion(struct device *dev,
> +					 struct acpi_device *parent,
> u64 addr)
> +{
> +	return;
> +}
> +
>  static inline const char *acpi_dev_name(struct acpi_device *adev)
>  {
>  	return NULL;

For me seems this one can go separately. Rafael, what do you think?

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy