Hi! > Introduction of the Platform Environment Control Interface (PECI) bus > device driver. PECI is a one-wire bus interface that provides a > communication channel between Intel processor and chipset components to > external monitoring or control devices. PECI is designed to support the > following sideband functions: > > * Processor and DRAM thermal management > - Processor fan speed control is managed by comparing Digital Thermal > Sensor (DTS) thermal readings acquired via PECI against the > processor-specific fan speed control reference point, or TCONTROL. > Both TCONTROL and DTS thermal readings are accessible via the processor > PECI client. These variables are referenced to a common temperature, > the TCC activation point, and are both defined as negative offsets from > that reference. > - PECI based access to the processor package configuration space provides > a means for Baseboard Management Controllers (BMC) or other platform > management devices to actively manage the processor and memory power > and thermal features. > > * Platform Manageability > - Platform manageability functions including thermal, power, and error > monitoring. Note that platform 'power' management includes monitoring > and control for both the processor and DRAM subsystem to assist with > data center power limiting. > - PECI allows read access to certain error registers in the processor MSR > space and status monitoring registers in the PCI configuration space > within the processor and downstream devices. > - PECI permits writes to certain registers in the processor PCI > configuration space. > > * Processor Interface Tuning and Diagnostics > - Processor interface tuning and diagnostics capabilities > (Intel(c) Interconnect BIST). The processors Intel(c) Interconnect > Built In Self Test (Intel(c) IBIST) allows for infield diagnostic > capabilities in the Intel UPI and memory controller interfaces. PECI > provides a port to execute these diagnostics via its PCI Configuration > read and write capabilities. > > * Failure Analysis > - Output the state of the processor after a failure for analysis via > Crashdump. > > PECI uses a single wire for self-clocking and data transfer. The bus > requires no additional control lines. The physical layer is a self-clocked > one-wire bus that begins each bit with a driven, rising edge from an idle > level near zero volts. The duration of the signal driven high depends on > whether the bit value is a logic '0' or logic '1'. PECI also includes > variable data transfer rate established with every message. In this way, > it is highly flexible even though underlying logic is simple. > > The interface design was optimized for interfacing to Intel processor and > chipset components in both single processor and multiple processor > environments. The single wire interface provides low board routing > overhead for the multiple load connections in the congested routing area > near the processor and chipset components. Bus speed, error checking, and > low protocol overhead provides adequate link bandwidth and reliability to > transfer critical device operating conditions and configuration > information. > > This implementation provides the basic framework to add PECI extensions > to the Linux bus and device models. A hardware specific 'Adapter' driver > can be attached to the PECI bus to provide sideband functions described > above. It is also possible to access all devices on an adapter from > userspace through the /dev interface. A device specific 'Client' driver > also can be attached to the PECI bus so each processor client's features > can be supported by the 'Client' driver through an adapter connection in > the bus. This patch set includes Aspeed 24xx/25xx PECI driver and a generic > PECI hwmon driver as the first implementation for both adapter and client > drivers on the PECI bus framework. Ok, how does this interact with ACPI/SMM BIOS/Secure mode code? Does Linux _need_ to control the fan? Or is SMM BIOS capable of doing all the work itself and Linux has just read-only access for monitoring purposes? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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