Date:   Mon, 10 Aug 2020 20:12:07 +0530
From:   Umesh A <umeshlinux123@...il.com>
To:     david.e.box@...ux.intel.com
Cc:     lee.jones@...aro.org, dvhart@...radead.org, andy@...radead.org,
        bhelgaas@...gle.com, alexander.h.duyck@...ux.intel.com,
        linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH V5 0/3] Intel Platform Monitoring Technology

MCTP and PLDM are the latest in Platform management Technology. Sw
application and drivers can be implemented on the PCIe platform.
Previously I spent some time on this.

On Mon, Aug 10, 2020 at 7:49 PM David E. Box
<david.e.box@...ux.intel.com> wrote:
>
> Friendly ping.
>
> On Wed, 2020-07-29 at 14:37 -0700, David E. Box wrote:
> > Intel Platform Monitoring Technology (PMT) is an architecture for
> > enumerating and accessing hardware monitoring capabilities on a
> > device.
> > With customers increasingly asking for hardware telemetry, engineers
> > not
> > only have to figure out how to measure and collect data, but also how
> > to
> > deliver it and make it discoverable. The latter may be through some
> > device
> > specific method requiring device specific tools to collect the data.
> > This
> > in turn requires customers to manage a suite of different tools in
> > order to
> > collect the differing assortment of monitoring data on their
> > systems.  Even
> > when such information can be provided in kernel drivers, they may
> > require
> > constant maintenance to update register mappings as they change with
> > firmware updates and new versions of hardware. PMT provides a
> > solution for
> > discovering and reading telemetry from a device through a hardware
> > agnostic
> > framework that allows for updates to systems without requiring
> > patches to
> > the kernel or software tools.
> >
> > PMT defines several capabilities to support collecting monitoring
> > data from
> > hardware. All are discoverable as separate instances of the PCIE
> > Designated
> > Vendor extended capability (DVSEC) with the Intel vendor code. The
> > DVSEC ID
> > field uniquely identifies the capability. Each DVSEC also provides a
> > BAR
> > offset to a header that defines capability-specific attributes,
> > including
> > GUID, feature type, offset and length, as well as configuration
> > settings
> > where applicable. The GUID uniquely identifies the register space of
> > any
> > monitor data exposed by the capability. The GUID is associated with
> > an XML
> > file from the vendor that describes the mapping of the register space
> > along
> > with properties of the monitor data. This allows vendors to perform
> > firmware updates that can change the mapping (e.g. add new metrics)
> > without
> > requiring any changes to drivers or software tools. The new mapping
> > is
> > confirmed by an updated GUID, read from the hardware, which software
> > uses
> > with a new XML.
> >
> > The current capabilities defined by PMT are Telemetry, Watcher, and
> > Crashlog.  The Telemetry capability provides access to a continuous
> > block
> > of read only data. The Watcher capability provides access to hardware
> > sampling and tracing features. Crashlog provides access to device
> > crash
> > dumps.  While there is some relationship between capabilities
> > (Watcher can
> > be configured to sample from the Telemetry data set) each exists as
> > stand
> > alone features with no dependency on any other. The design therefore
> > splits
> > them into individual, capability specific drivers. MFD is used to
> > create
> > platform devices for each capability so that they may be managed by
> > their
> > own driver. The PMT architecture is (for the most part) agnostic to
> > the
> > type of device it can collect from. Devices nodes are consequently
> > generic
> > in naming, e.g. /dev/telem<n> and /dev/smplr<n>. Each capability
> > driver
> > creates a class to manage the list of devices supporting
> > it.  Software can
> > determine which devices support a PMT feature by searching through
> > each
> > device node entry in the sysfs class folder. It can additionally
> > determine
> > if a particular device supports a PMT feature by checking for a PMT
> > class
> > folder in the device folder.
> >
> > This patch set provides support for the PMT framework, along with
> > support
> > for Telemetry on Tiger Lake.
> >
> > Changes from V4:
> >       - Replace MFD with PMT in driver title
> >       - Fix commit tags in chronological order
> >       - Fix includes in alphabetical order
> >       - Use 'raw' string instead of defines for device names
> >       - Add an error message when returning an error code for
> >         unrecognized capability id
> >       - Use dev_err instead of dev_warn for messages when returning
> >         an error
> >       - Change while loop to call pci_find_next_ext_capability once
> >       - Add missing continue in while loop
> >       - Keep PCI platform defines using PCI_DEVICE_DATA magic tied to
> >         the pci_device_id table
> >       - Comment and kernel message cleanup
> >
> > Changes from V3:
> >       - Write out full acronym for DVSEC in PCI patch commit message
> > and
> >         add 'Designated' to comments
> >       - remove unused variable caught by kernel test robot <
> > lkp@...el.com>
> >       - Add required Co-developed-by signoffs, noted by Andy
> >       - Allow access using new CAP_PERFMON capability as suggested by
> >         Alexey Bundankov
> >       - Fix spacing in Kconfig, noted by Randy
> >       - Other style changes and fixups suggested by Andy
> >
> > Changes from V2:
> >       - In order to handle certain HW bugs from the telemetry
> > capability
> >         driver, create a single platform device per capability
> > instead of
> >         a device per entry. Add the entry data as device resources
> > and
> >         let the capability driver manage them as a set allowing for
> >         cleaner HW bug resolution.
> >       - Handle discovery table offset bug in intel_pmt.c
> >       - Handle overlapping regions in intel_pmt_telemetry.c
> >       - Add description of sysfs class to testing ABI.
> >       - Don't check size and count until confirming support for the
> > PMT
> >         capability to avoid bailing out when we need to skip it.
> >       - Remove unneeded header file. Move code to the intel_pmt.c,
> > the
> >         only place where it's needed.
> >       - Remove now unused platform data.
> >       - Add missing header files types.h, bits.h.
> >       - Rename file name and build options from telem to telemetry.
> >       - Code cleanup suggested by Andy S.
> >       - x86 mailing list added.
> >
> > Changes from V1:
> >       - In the telemetry driver, set the device in device_create() to
> >         the parent PCI device (the monitoring device) for clear
> >         association in sysfs. Was set before to the platform device
> >         created by the PCI parent.
> >       - Move telem struct into driver and delete unneeded header
> > file.
> >       - Start telem device numbering from 0 instead of 1. 1 was used
> >         due to anticipated changes, no longer needed.
> >       - Use helper macros suggested by Andy S.
> >       - Rename class to pmt_telemetry, spelling out full name
> >       - Move monitor device name defines to common header
> >       - Coding style, spelling, and Makefile/MAINTAINERS ordering
> > fixes
> >
> > David E. Box (3):
> >   PCI: Add defines for Designated Vendor-Specific Extended Capability
> >   mfd: Intel Platform Monitoring Technology support
> >   platform/x86: Intel PMT Telemetry capability driver
> >
> >  .../ABI/testing/sysfs-class-pmt_telemetry     |  46 ++
> >  MAINTAINERS                                   |   6 +
> >  drivers/mfd/Kconfig                           |  10 +
> >  drivers/mfd/Makefile                          |   1 +
> >  drivers/mfd/intel_pmt.c                       | 220 +++++++++
> >  drivers/platform/x86/Kconfig                  |  10 +
> >  drivers/platform/x86/Makefile                 |   1 +
> >  drivers/platform/x86/intel_pmt_telemetry.c    | 448
> > ++++++++++++++++++
> >  include/uapi/linux/pci_regs.h                 |   5 +
> >  9 files changed, 747 insertions(+)
> >  create mode 100644 Documentation/ABI/testing/sysfs-class-
> > pmt_telemetry
> >  create mode 100644 drivers/mfd/intel_pmt.c
> >  create mode 100644 drivers/platform/x86/intel_pmt_telemetry.c
> >
>

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