Re: [PATCH V4 0/3] Intel Platform Monitoring Technology

From: Andy Shevchenko
Date: Mon Jul 27 2020 - 06:24:01 EST

On Fri, Jul 17, 2020 at 10:05 PM 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.

I assume this goes thru MFD tree.

> 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@xxxxxxxxx>
> - 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 ++
> drivers/mfd/Kconfig | 10 +
> drivers/mfd/Makefile | 1 +
> drivers/mfd/intel_pmt.c | 215 +++++++++
> 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, 742 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
> --
> 2.20.1

With Best Regards,
Andy Shevchenko