Modem-Directed AP Boot Flow with DMA and Crypto Idle States
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Solution Overview
Problem
Existing systems and methods fail to leverage power savings during the boot sequence of application processors (APs) and their associated dynamic random-access memory (DRAM) in portable computing devices (PCDs) by keeping them in an active state throughout the process.
Innovation Solution
A modem-directed application processor boot flow is implemented, utilizing a direct memory access (DMA) engine and a crypto engine to read and calculate hash values for metadata and data segments, allowing the AP to transition into an idle state during processing, thereby reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the application processor boots independently before the modem, then the application processor can start its boot flow earlier, but the system cannot utilize modem-ready hardware resources (GPU, NPU, DSP) until the application processor is fully booted
Solution Approach 1:
The modem completes its boot flow and prepares hardware resources (GPU, NPU, DSP) in advance before the application processor needs them. The modem boots independently and initializes hardware resources early, allowing the application processor to directly utilize these pre-prepared resources upon completion of its own boot, thereby eliminating idle time and accelerating overall system startup.
2Reliability
If the application processor waits for the modem to complete booting, then hardware resources can be properly initialized, but the application processor experiences boot delays
Solution Approach 1:
The modem performs hardware resource initialization in advance during its own boot process, rather than waiting for the application processor. This preliminary action ensures that when the application processor completes its boot, the hardware resources are already ready and can be immediately utilized, eliminating the need for the application processor to wait.
Solution Approach 2:
The boot process is segmented into independent phases: the modem completes its boot and hardware initialization first, then the application processor boots and utilizes the pre-initialized resources. This segmentation allows parallel execution of modem boot and application processor boot, with the modem's hardware preparation occurring independently before the application processor needs it.
3Adaptability or versatility
If traditional separate boot flows are used, then each processor can boot independently, but hardware resources remain inaccessible during the application processor's boot phase
Solution Approach 1:
The modem performs preliminary hardware initialization during its independent boot process, preparing GPU, NPU, and DSP resources in advance. This allows the application processor to maintain its independent boot capability while also enabling early availability of hardware resources, thereby improving system startup efficiency without sacrificing autonomy.
Solution Approach 2:
The modem acts as an intermediary that prepares hardware resources before the application processor needs them. The modem's boot process serves as a preparatory stage that enables subsequent efficient utilization of hardware resources by the application processor, bridging the gap between independent booting and resource availability.
Data Source
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AI summary
Various embodiments of methods and systems for a modem-directed application processor boot flow in a portable computing device ("PCD") are disclosed. An exemplary method includes an application processor that transitions into an idle state, such as a WFI state, for durations of time during a boot sequence that coincide with processing by a DMA engine and/or crypto engine. That is, the application processor may "sleep" while the DMA engine and/or crypto engine process workloads in response to instructions they received from the application processor.