Speaker
Description
Currently when booting in Devicetree mode the kernel will fully disable the ACPI subsystem. On WoA Snapdragon laptops where the factory Windows OS actually boots using the ACPI tables this is not necessarily desirable.
The purpose of this session is to present and discuss a proposal for a new DT-ACPI hybrid mode, in which while booting with Devicetree:
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The ACPI tables are still parsed and ACPI fwnodes are made available for device-drivers to use for (extra) information.
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Some devices may even be fully enumerated through ACPI e.g. enumerate I2C clients through ACPI for an I2C controller which itself is described in DT.
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Going futher: use ACPI GPIO-IRQ event handlers + I2C opregion support to let ACPI handle a laptops embedded controller connected over I2C and using the ACPI battery device (backed by the EC) to expose battery state information in a laptop-model agnostic way like how laptop batteries are handled on x86 laptops.
Note on current laptops Linux cannot boot using ACPI due to some information missing from the ACPI tables. People are working on changing this so that for future WoA Snapdragon laptops Linux can boot using ACPI only without requiring Devicetree.
An early RFC patch-series implementing 1. + 2. has been posted upstream.