Message-ID: <74c03fe9fea12f4b056bf694a0d03d5200244231.camel@linux.intel.com>
Date:   Mon, 10 Aug 2020 07:15:42 -0700
From:   "David E. Box" <david.e.box@...ux.intel.com>
To:     lee.jones@...aro.org, dvhart@...radead.org, andy@...radead.org,
        bhelgaas@...gle.com, alexander.h.duyck@...ux.intel.com
Cc:     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

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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