From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooks <andrew.cooks@opengear.com>
Subject: Re: [PATCH 3/3] i2c: add ACPI support for i2c-piix4
Date: Tue, 30 Jan 2018 11:43:46 +1000
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To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jean Delvare <jdelvare@suse.com>, Wolfram Sang <wsa@the-dreams.de>, "open list:I2C/SMBUS CONTROLLER DRIVERS FOR PC" <linux-i2c@vger.kernel.org>, open list <linux-kernel@vger.kernel.org>

Hi Andy

On 29/01/18 23:30, Andy Shevchenko wrote:
> On Mon, Jan 29, 2018 at 5:54 AM, Andrew Cooks <andrew.cooks@opengear.com> wrote:
>> This enables the i2c-piix4 SMBus controller driver to enumerate I2C
>> slave devices using ACPI. It builds on the related I2C mux device work
>> in commit 8eb5c87a92c0 ("i2c: add ACPI support for I2C mux ports")
>>
>> In the i2c-piix4 driver the adapters are enumerated as:
>>  Main SMBus adapter Port 0, Port 2, ..., aux port (i.e., ASF adapter)
>>
>> However, in the AMD BKDG documentation[1], the implied order of ports is:
>>  Main SMBus adapter Port 0, ASF adapter, Port 2, Port 3, ...
>>
>> This ordering difference is unfortunate, and we assume that ACPI
>> developers will use the Linux ordering.
>>
>> [1] 52740 BIOS and Kernel Developer's Guide (BKDG) for AMD Family 16h
>> Models 30h-3Fh Processors
> 
>> +       if (has_acpi_companion(&dev->dev)) {
>> +               acpi_preset_companion(&adap->dev,
>> +                                     ACPI_COMPANION(&dev->dev),
>> +                                     piix4_adapter_count++);
>> +       }
> 
> Wouldn't be enough just following:
> 
>      ACPI_COMPANION_SET(&adap->dev, ACPI_COMPANION(&dev->dev));

In the ACPI DSDT, I've modeled the topology as follows:

Device(SBUS) {
        Name(_ADR, 0x00140000)
        Name(_HID, "SMB0001") // SMBus CMI spec uses (invalid hid) "SMBUS01"

        Device(CH00) {
                Name(_ADR, 0) // main SMBus adapter, Port 0
                Name (_STR, Unicode ("Main SMBus adapter, Port 0"))
        }

        Device(CH01) {
                Name(_ADR, 1) // main SMBus Port 2 (Port 1 label is undefined)
                Name (_STR, Unicode ("Main SMBus adapter, Port 2"))
        }

        Device (CH02) {
                Name(_ADR, 2) // ASF adapter (what Linux calls 'aux port')
                Name (_STR, Unicode ("AUX / ASF SMBus adapter"))
        }
}

That is why each piix4 adapter matches a CH0? device that is descendant from the SBUS device in ACPI.

It is similar to the topology shown in commit 8eb5c87a ("i2c: add ACPI support for I2C mux ports")

> 
> ?
> 
> Or if this increment is needed:
> 
> struct acpi_device *adev = ACPI_COMPANION(&dev->dev);
> 
> if (adev) {
>     ACPI_COMPANION_SET(&adap->dev, adev);
>     piix4_adapter_count++);
> }
> 

Thanks!

a.