• Geert Uytterhoeven's avatar
    base: soc: Allow early registration of a single SoC device · 6e12db37
    Geert Uytterhoeven authored
    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: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
    Acked-by: default avatarArnd Bergmann <arnd@arndb.de>
    6e12db37
soc.c 6.17 KB