linux-kernel - Re: [PATCH V8 0/5] Intel Platform Monitoring Technology

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Date:   Wed, 28 Oct 2020 18:50:16 -0700
From:   "David E. Box" <david.e.box@...ux.intel.com>
To:     Hans de Goede <hdegoede@...hat.com>, lee.jones@...aro.org,
        dvhart@...radead.org, andy@...radead.org, bhelgaas@...gle.com,
        alexey.budankov@...ux.intel.com
Cc:     linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH V8 0/5] Intel Platform Monitoring Technology

On Tue, 2020-10-27 at 12:28 +0100, Hans de Goede wrote:
> Hi,
> 
> On 10/3/20 3:31 AM, 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. 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.
> 
> The entire series looks good to me, so you may add my:
> 
> Reviewed-by: Hans de Goede <hdegoede@...hat.com>

Thanks. I did send out a V9 after rebasing and noticing that I
accidentally dropped a change in the MFD driver between V7 and V8. This
was added back. I also took the opportunity to get rid of a nuisance
dev_warn.

David