linux-kernel - Re: [PATCH 3/3] i2c: add ACPI support for i2c-piix4

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <56310e2c-eedc-a71a-3247-d418ec10052d@opengear.com>
Date:   Tue, 30 Jan 2018 11:43:46 +1000
From:   Andrew Cooks <andrew.cooks@...ngear.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Jean Delvare <jdelvare@...e.com>, Wolfram Sang <wsa@...-dreams.de>,
        "open list:I2C/SMBUS CONTROLLER DRIVERS FOR PC" 
        <linux-i2c@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] i2c: add ACPI support for i2c-piix4

Hi Andy

On 29/01/18 23:30, Andy Shevchenko wrote:
> On Mon, Jan 29, 2018 at 5:54 AM, Andrew Cooks <andrew.cooks@...ngear.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.