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

[Quan Nguyen]

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@xxxxxxxxxxxxxxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxxxxxxxxxxxxxx
> > +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/

> > +
> > +		See [1] below for the format details.
> > +
> > +		The detail of each sysfs entries is as below:
> > +		+-------------+---------------------------------------------------------+
> > +		|   Error     |                   Sysfs entry                           |
> > +		+-------------+---------------------------------------------------------+
> > +		| Core's CE   | /sys/bus/platform/devices/smpro-errmon.*/errors_core_ce |
> > +		| Core's UE   | /sys/bus/platform/devices/smpro-errmon.*/errors_core_ue |
> > +		| Memory's CE | /sys/bus/platform/devices/smpro-errmon.*/errors_mem_ce  |
> > +		| Memory's UE | /sys/bus/platform/devices/smpro-errmon.*/errors_mem_ue  |
> > +		| PCIe's CE   | /sys/bus/platform/devices/smpro-errmon.*/errors_pcie_ce |
> > +		| PCIe's UE   | /sys/bus/platform/devices/smpro-errmon.*/errors_pcie_ue |
> > +		| Other's CE  | /sys/bus/platform/devices/smpro-errmon.*/errors_other_ce|
> > +		| Other's UE  | /sys/bus/platform/devices/smpro-errmon.*/errors_other_ue|
> > +		+-------------+---------------------------------------------------------+
> > +		UE: Uncorrect-able Error
> > +		CE: Correct-able Error
> > +
> > +		[1] Section 3.3 Ampere (Vendor-Specific) Error Record Formats,
> > +		    Altra Family RAS Supplement.
> > +
> > +
> > +What:           /sys/bus/platform/devices/smpro-errmon.*/errors_[smpro|pmpro]
> > +KernelVersion:	5.14
> > +Contact:	quan@xxxxxxxxxxxxxxxxxxxxxx
> > +Description:
> > +		(RO) Contains the internal firmware error record printed as hex format
> > +		as below:
> > +
> > +		A BB C DD EEEE FFFFFFFF
>
> Again this isn't a good sysfs entry.  You should never have to parse a
> sysfs file except for a single value.
>
> thanks,
>
> greg k-h

This error is also unable to separate further as well.

Thanks Greg for the review.
- Quan