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Power Management [clear filter]
Monday, September 23
 

2:00pm

SAN19-101 Thermal Governors: How to pick the right one
With higher Gigahertz and multiple cores packed in a SoC the need for thermal management for ARM based SoCs gets more and more critical. Thermal governors that define the policy for thermal management play a pivotal role in ensuring thermal safety of the device. Choosing the right one ensures the device performs optimally with in the thermal budget.

In this presentation Keerthy Jagadeesh, Co-maintainer TI BANDGAP AND THERMAL DRIVER explores the behavior of existing governors like step_wise, fair_share, bang_bang governors on A15 based DRA7 SoCs as an example. Governors perform differently based on the Number of Cores the SoC packs, the process node and the use cases. The results on DRA7 family of SoCs will be used to provide guide lines while choosing a particular thermal governor for a given SoC based on the above mentioned parameters.

Speakers
avatar for Keerthy Jagadeesh

Keerthy Jagadeesh

Software Engineer, Texas Instruments
Keerthy Jagadeesh is part of Linux core product development team of the Texas Intruments and has been an active linux contibutor for the past 8+ years. He has worked mainly on thermal management for TI SoCs, PMIC driver development, Implementing low power modes for AM437x SoCs. Currently... Read More →



Monday September 23, 2019 2:00pm - 2:25pm
Sunset IV (Session 2)

4:00pm

SAN19-117 An Overview of the opensource Arm System Control Processor (SCP) Firmware Architecture
The Arm SCP-Firmware provides a reference firmware implementation for the System Control Processor (SCP) and Manageability Control Processor (MCP) components found in several Arm Compute Sub-Systems. It provides Power Management and System Control functionality that is compliant with the Arm System Control and Management Interface (SCMI). The SCP-Firmware is based on a modular design which caters to multiple deployment models. The SCP Firmware lends itself to easy deployment, whether RTOS or bare metal. It is based on a core Framework which provides common services to all modules. The Modules plug into the framework and implement functionalities which can be chosen on a per-platform basis. This provides complete flexibility for any platform or implementation to provide their own modules and ‘special implementations’ as required. Additionally, the SCP Firmware abstracts Execution Context requirements enabling it to be deployed in a wide variety on systems and architectures and even run on host environments.

In my presentation, I will talk about how the SCP firmware positions itself in Power management paradigms based on the division of responsibilities between the OS kernel and the firmware. We will briefly go through the Framework and Module design and how they provide flexibility to a platform to enable fast deployment. We will also talk about the way the various firmware components communicate with each other using events and notifications, which can be well abstracted from the underlying execution context. The advantages that the SCP firmware provides due to its lightweight and flexible scheduling model which can scale from single-threaded to multi-threaded will be discussed. Finally, we will discuss the guidelines for developing code based on the opensource SCP-Firmware and the benefits of doing so.

Speakers
avatar for Souvik Chakravarty

Souvik Chakravarty

Staff Software Engineer, ARM Limited
Souvik is a Staff Software Engineer in the Architecture and Technology Group at Arm, where his primary areas of focus are System and Power Management software standards and specifications.



Monday September 23, 2019 4:00pm - 4:50pm
Pacific Room (Keynote)
 
Tuesday, September 24
 

11:00am

SAN19-207 SCMI server in secure world
The System Control and Management Interface (SCMI) is a set of operating system-independent software interfaces that are used in system resources management that has been originally specified to standardize the interface between Application Processors and the power coprocessor. Nevertheless, systems don't always have a dedicated coprocessor for system resources management but still need to safely manage them.The secure world is a good candidate as it uses some of these critical resources. Instead of defining a new custom interface, it has been decided to enable a SCMI server in secure world that will handle system request from all agents of the system being the non secure world of AP or other processors of the system.
This talk will present the SCMI server implementation in secure world, the constraints that have driven the implementation choices, the open items and next features. During the talk, we will have a special focus on the OP-TEE arm32 implementation.

Speakers
avatar for Souvik Chakravarty

Souvik Chakravarty

Staff Software Engineer, ARM Limited
Souvik is a Staff Software Engineer in the Architecture and Technology Group at Arm, where his primary areas of focus are System and Power Management software standards and specifications.
avatar for Vincent Guittot

Vincent Guittot

Technical Leader, Linaro
Vincent has worked on developing drivers for various peripherals and coprocessors in mobile phones during 12 years. In 2005, he began to focus on mobile phones that ran Linux then Android and spent the last years of this period to optimize the power consumption of android platforms... Read More →


Tuesday September 24, 2019 11:00am - 11:50am
Sunset V (Session 1)

12:00pm

SAN19-213 A Guide to enabling new Power Management & System Control Models via Arm SCMIv2.0
Continuing from Linaro Connect BKK19, where the Arm SCMI Roadmap was unveiled, we have released SCMI specification version 2.0 in July/August 2019. This version of the specification enables new usage models to cater to Power Management and System Control requirements in Mobile, Embedded and Automotive markets.

Cost sensitive SoC designs may not opt for a stand-alone microcontroller for System Control. For such systems, SCMIv2.0 enables the System Control Firmware to be resident in the secure world. We shall go over the requirements to implement the kernel and firmware code for such systems to comply with SCMI.

SCMIv2.0 introduces the concept of Per-Agent Resource Isolation Domains. Many SoCs today implement multiple PE Clusters where each cluster runs a different OS instance. Such systems require the SoC resources to be partitioned dynamically among the various agents (we may model each such cluster to be a SCMI agent). SCMIv2.0 introduces new commands to achieve this. In our session, we shall talk about how this can be done using the new SCMIv2.0 commands, and the agent-id and transport requirements and semantics for such a model to work. We will also provide an overview how such a model might work for Virtualized Systems. The presentation will cover how newly introduced Power Domain pre-notifications can be used for co-operative Power Management according to user defined policies in such systems.

SCMIv2.0 introduces FastChannels. We will provide an overview of its requirements and how FastChannels can be enabled for latency critical operations. We will also touch upon the Reset Management Protocol which can be used for device resets. Finally we will walk-through the features planned to be introduced in the next version of SCMI.

Speakers
avatar for Souvik Chakravarty

Souvik Chakravarty

Staff Software Engineer, ARM Limited
Souvik is a Staff Software Engineer in the Architecture and Technology Group at Arm, where his primary areas of focus are System and Power Management software standards and specifications.



Tuesday September 24, 2019 12:00pm - 12:50pm
Sunset V (Session 1)

2:00pm

SAN19-220 Deep dive in the scheduler
This training will present the details of some parts of the scheduler like the task placement during wake up path, the cgroup in the scheduler or how CPU compute capacity is used to balance tasks on the system.
The training will continue from where it stopped at HKG19.

Speakers
avatar for Vincent Guittot

Vincent Guittot

Technical Leader, Linaro
Vincent has worked on developing drivers for various peripherals and coprocessors in mobile phones during 12 years. In 2005, he began to focus on mobile phones that ran Linux then Android and spent the last years of this period to optimize the power consumption of android platforms... Read More →


Tuesday September 24, 2019 2:00pm - 2:50pm
Sunset V (Session 1)
 
Thursday, September 26
 

2:00pm

SAN19-421 Training: Device power management for idle
ARM platforms often supports sophisticated power management, to for example allow unused parts on a running system, to be put into low power states, which prevents energy from being drained.

However, it can be a rather complicated task to deploy optimized power management support in a driver in the Linux kernel, especially when it comes to idle management. A couple of frameworks are there to help and these comes with corresponding callback functions, that may be assigned on per device basis. The driver developer needs detailed knowledge about these frameworks, especially when the goal is to reach the best possible energy efficient behavior.

In this session, we look into the concepts for system wide suspend and the corresponding low power states, such as suspend to ram, suspend to idle and suspend to disk.

Additionally, for more fine grained power management per device, some best practices are explained of how to deploy support for runtime PM and PM domains (in particular the generic PM domain) .

Speakers
avatar for Ulf Hansson

Ulf Hansson

Senior Kernel Engineer, Linaro
Ulf has a very long experience of using Linux and has been contributing the Linux kernel development for many years by now. He maintains the MMC subsystem and the generic PM domain in the Linux kernel, but also spends lots of time reviewing various changes related to power management... Read More →



Thursday September 26, 2019 2:00pm - 2:50pm
Sunset V (Session 1)