linux-kernel - Re: [RESEND PATCH v4 4/4] powerpc/papr_scm: Document papr

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Date:   Tue, 7 Sep 2021 18:03:48 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Kajol Jain <kjain@...ux.ibm.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux NVDIMM <nvdimm@...ts.linux.dev>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Weiny, Ira" <ira.weiny@...el.com>,
        Vishal L Verma <vishal.l.verma@...el.com>,
        maddy@...ux.ibm.com, Santosh Sivaraj <santosh@...six.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Vaibhav Jain <vaibhav@...ux.ibm.com>,
        atrajeev@...ux.vnet.ibm.com, Thomas Gleixner <tglx@...utronix.de>,
        rnsastry@...ux.ibm.com
Subject: Re: [RESEND PATCH v4 4/4] powerpc/papr_scm: Document papr_scm sysfs
 event format entries

On Thu, Sep 2, 2021 at 10:11 PM Kajol Jain <kjain@...ux.ibm.com> wrote:
>
> Details is added for the event, cpumask and format attributes
> in the ABI documentation.
>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Reviewed-by: Madhavan Srinivasan <maddy@...ux.ibm.com>
> Tested-by: Nageswara R Sastry <rnsastry@...ux.ibm.com>
> Signed-off-by: Kajol Jain <kjain@...ux.ibm.com>
> ---
>  Documentation/ABI/testing/sysfs-bus-papr-pmem | 31 +++++++++++++++++++
>  1 file changed, 31 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-papr-pmem b/Documentation/ABI/testing/sysfs-bus-papr-pmem
> index 95254cec92bf..4d86252448f8 100644
> --- a/Documentation/ABI/testing/sysfs-bus-papr-pmem
> +++ b/Documentation/ABI/testing/sysfs-bus-papr-pmem
> @@ -61,3 +61,34 @@ Description:
>                 * "CchRHCnt" : Cache Read Hit Count
>                 * "CchWHCnt" : Cache Write Hit Count
>                 * "FastWCnt" : Fast Write Count
> +
> +What:          /sys/devices/nmemX/format
> +Date:          June 2021
> +Contact:       linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>, nvdimm@...ts.linux.dev,
> +Description:   (RO) Attribute group to describe the magic bits
> +                that go into perf_event_attr.config for a particular pmu.
> +                (See ABI/testing/sysfs-bus-event_source-devices-format).
> +
> +                Each attribute under this group defines a bit range of the
> +                perf_event_attr.config. Supported attribute is listed
> +                below::
> +
> +                   event  = "config:0-4"  - event ID
> +
> +               For example::
> +                   noopstat = "event=0x1"
> +
> +What:          /sys/devices/nmemX/events

That's not a valid sysfs path. Did you mean /sys/bus/nd/devices/nmemX?

> +Date:          June 2021
> +Contact:       linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>, nvdimm@...ts.linux.dev,
> +Description:    (RO) Attribute group to describe performance monitoring
> +                events specific to papr-scm. Each attribute in this group describes
> +                a single performance monitoring event supported by this nvdimm pmu.
> +                The name of the file is the name of the event.
> +                (See ABI/testing/sysfs-bus-event_source-devices-events).

Given these events are in the generic namespace the ABI documentation
should be generic as well. So I think move these entries to
Documentation/ABI/testing/sysfs-bus-nvdimm directly.

You can still mention papr-scm, but I would expect something like:

What:           /sys/bus/nd/devices/nmemX/events
Date:           September 2021
KernelVersion:  5.16
Contact:        Kajol Jain <kjain@...ux.ibm.com>
Description:
                (RO) Attribute group to describe performance monitoring events
                for the nvdimm memory device. Each attribute in this group
                describes a single performance monitoring event supported by
                this nvdimm pmu.  The name of the file is the name of the event.
                (See ABI/testing/sysfs-bus-event_source-devices-events). A
                listing of the events supported by a given nvdimm provider type
                can be found in Documentation/driver-api/nvdimm/$provider, for
                example: Documentation/driver-api/nvdimm/papr-scm.



> +
> +What:          /sys/devices/nmemX/cpumask
> +Date:          June 2021
> +Contact:       linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>, nvdimm@...ts.linux.dev,
> +Description:   (RO) This sysfs file exposes the cpumask which is designated to make
> +                HCALLs to retrieve nvdimm pmu event counter data.

Seems this one would be provider generic, so no need to refer to PPC
specific concepts like HCALLs.