linux-kernel - Re: [PATCH v7 9/9] docs: ABI: testing: Document the Ampere Altra Family's SMpro sysfs interfaces

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Date:   Fri, 25 Mar 2022 14:14:37 +0700
From:   Quan Nguyen <quan@...amperecomputing.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Lee Jones <lee.jones@...aro.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Jonathan Corbet <corbet@....net>,
        Derek Kiernan <derek.kiernan@...inx.com>,
        Dragan Cvetic <dragan.cvetic@...inx.com>,
        Arnd Bergmann <arnd@...db.de>,
        Thu Nguyen <thu@...amperecomputing.com>,
        Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "open list:HARDWARE MONITORING" <linux-hwmon@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Open Source Submission <patches@...erecomputing.com>,
        Phong Vo <phong@...amperecomputing.com>,
        "Thang Q . Nguyen" <thang@...amperecomputing.com>
Subject: Re: [PATCH v7 9/9] docs: ABI: testing: Document the Ampere Altra
 Family's SMpro sysfs interfaces



On 21/03/2022 17:03, Greg Kroah-Hartman wrote:
> On Mon, Mar 21, 2022 at 04:46:36PM +0700, Quan Nguyen wrote:
>>
>>
>> On 21/03/2022 15:23, Greg Kroah-Hartman wrote:
>>> On Mon, Mar 21, 2022 at 03:13:55PM +0700, Quan Nguyen wrote:
>>>> Add documentation for the Ampere(R)'s Altra(R) SMpro sysfs interfaces
>>>>
>>>> Signed-off-by: Quan Nguyen <quan@...amperecomputing.com>
>>>> ---
>>>> Changes in v7:
>>>>     + First introduce in v7     [Greg]
>>>>
>>>>    .../sysfs-bus-platform-devices-ampere-smpro   | 133 ++++++++++++++++++
>>>>    1 file changed, 133 insertions(+)
>>>>    create mode 100644 Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro
>>>>
>>>> diff --git a/Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro b/Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro
>>>> new file mode 100644
>>>> index 000000000000..9bfd8d6d0f71
>>>> --- /dev/null
>>>> +++ b/Documentation/ABI/testing/sysfs-bus-platform-devices-ampere-smpro
>>>> @@ -0,0 +1,133 @@
>>>> +What:		/sys/bus/platform/devices/smpro-errmon.*/errors_[core|mem|pcie|other]_[ce|ue]
>>>
>>> Please split this out as one entry per file.
>>>
>>
>> These sysfs share same format of HW errors (the 48-byte Arm vendor specific
>> HW error record) but for separate HW domains: Core, PCIe, Mem... etc
>>
>>>> +KernelVersion:	5.14
>>>
>>> 5.14 is a long time ago.
>>>
>>>> +Contact:	quan@...amperecomputing.com
>>>> +Description:
>>>> +		(RO) Contains the 48-byte Ampere (Vendor-Specific) Error Record, see [1]
>>>> +		printed in hex format as below:
>>>> +
>>>> +		AA BB CCCC DDDDDDDD DDDDDDDDDDDDDDDD DDDDDDDDDDDDDDDD \
>>>> +		   DDDDDDDDDDDDDDDD DDDDDDDDDDDDDDDD DDDDDDDDDDDDDDDD
>>>> +		Where:
>>>> +		  AA       : Error Type
>>>> +		  BB       : Subtype
>>>> +		  CCCC     : Instance
>>>> +		  DDD...DDD: Similar to the Arm RAS standard error record
>>>
>>> No, this is not a valid sysfs file, sorry.  This should just be one
>>> value per file.
>>>
>>
>> This 48-byte value is unable to separate into smaller values because it
>> contain all information necessary to indicate a single HW error as per ARM
>> RAS supplement document [1]. The format is to make it read-able other than a
>> single 48-byte hex value.
>>
>> [1] https://developer.arm.com/documentation/ddi0587/latest/
> 
> Just export the 48 byte hex value and make userspace split it up if it
> wants to do so.  Don't do things in the kernel that can be done in
> userspace.
> 

Thanks Greg for the suggestion,
Will do this in my next version.

Thanks,
- Quan