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base: soc: Allow early registration of a single SoC device
Commit 1da1b362 ("base: soc: Early register bus when needed") added support for early registration of SoC devices from a core_initcall(). However, some drivers need to check the SoC revision from an early_initcall(), which is even earlier. A specific example is the Renesas R-Car SYSC driver, which manages PM Domains and thus needs to be initialized from an early_initcall. Preproduction versions of the R-Car H3 SoC have an additional power area, which no longer exists on H3 ES2.0, so the R-Car SYSC driver needs to check the exact SoC revision before instantiating a PM Domain for that power area. While registering the SoC bus and device, and using soc_device_match(), from an early_initcall() do work, the "soc" directory and the "soc0" file end up wrongly in the sysfs root, as the "bus" resp. "devices" directories haven't been created yet. To fix this, allow to register a single SoC device early on. As long as the SoC bus isn't registered, soc_device_match() just matches against this early device. When the SoC bus is registered later, the early device is registered for real. Note that soc_device_register() returns NULL (no error, but also not a valid pointer) when registering an early device. Hence platform devices cannot be instantiated as children of the "soc0" node representing an early SoC device. This should not be an issue, as that practice has been deprecated for new platforms. Signed-off-by:Geert Uytterhoeven <geert+renesas@glider.be> Acked-by: