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Explore the challenges and potential solutions for powering up "discoverable bus-attached" devices on Device Tree (DT) based platforms in this comprehensive conference talk. Delve into the long-standing issue of devices requiring power-up configurations before bus enumeration, and understand why many DT-based platforms resort to marking resources as "always-on" as a temporary fix. Examine the limitations of devicetree in describing devices connected to buses like PCI, USB, and MMC, and learn about existing solutions such as MMC's pwrseq and the recent approach for USB onboard hubs. Investigate complex scenarios involving multi-functional devices like Qualcomm QCA Wifi and Bluetooth chips, and consider the challenges in resource management and driver probing. Discuss potential solutions, including the concept of a "power sequencer" and its placement within the Linux kernel subsystems. Analyze historical proposals, current implementations, and a possible proof-of-concept to address these issues. Gain insights into improving device discovery, power management, and overall system efficiency on DT-based platforms.
