Powering up "discoverable bus-attached" devices on DT-based platforms
summary
Linux DT platforms fail to power devices that must be live for bus enumeration, forcing marking regulators "always-on" and draining battery; example is the WCN6855 combo chip that needs a strict regulator/GPIO order so PCI cannot discover it. Existing fixes: MMC pwrseq, upstreamed USB onboard-hub (merged in 6.0) which creates a platform node to power hubs, and a proposed power sequencing subsystem to expose provider/consumer ops; alternative is PCI slot/hotplug-style platform drivers that power a slot before bus scan.
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chapters (7)
- 0:00Introduction and speaker background
- 3:53Discoverable vs non-discoverable buses
- 7:04Wi-Fi and Bluetooth use case on X1S
- 15:42Discovery process differences
- 21:51Power sequencing subsystem proposal
- 27:53USB onboard Hub solution
- 42:57Conclusion and future steps
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