• Douglas Anderson's avatar
    regulator: Set PROBE_PREFER_ASYNCHRONOUS for drivers that existed in 4.14 · 259b93b2
    Douglas Anderson authored
    Probing of regulators can be a slow operation and can contribute to
    slower boot times. This is especially true if a regulator is turned on
    at probe time (with regulator-boot-on or regulator-always-on) and the
    regulator requires delays (off-on-time, ramp time, etc).
    
    While the overall kernel is not ready to switch to async probe by
    default, as per the discussion on the mailing lists [1] it is believed
    that the regulator subsystem is in good shape and we can move
    regulator drivers over wholesale. There is no way to just magically
    opt in all regulators (regulators are just normal drivers like
    platform_driver), so we set PROBE_PREFER_ASYNCHRONOUS for all
    regulators found in 'drivers/regulator' individually.
    
    Given the number of drivers touched and the impossibility to test this
    ahead of time, it wouldn't be shocking at all if this caused a
    regression for someone. If there is a regression caused by this patch,
    it's likely to be one of the cases talked about in [1]. As a "quick
    fix", drivers involved in the regression could be fixed by changing
    them to PROBE_FORCE_SYNCHRONOUS. That being said, the correct fix
    would be to directly fix the problem that caused the issue with async
    probe.
    
    The approach here follows a similar approach that was used for the mmc
    subsystem several years ago [2]. In fact, I ran nearly the same python
    script to auto-generate the changes. The only thing I changed was to
    search for "i2c_driver", "spmi_driver", and "spi_driver" in addition
    to "platform_driver".
    
    [1] https://lore.kernel.org/r/06db017f-e985-4434-8d1d-02ca2100cca0@sirena.org.uk
    [2] https://lore.kernel.org/r/20200903232441.2694866-1-dianders@chromium.org/Signed-off-by: default avatarDouglas Anderson <dianders@chromium.org>
    Link: https://lore.kernel.org/r/20230316125351.1.I2a4677392a38db5758dee0788b2cea5872562a82@changeidSigned-off-by: default avatarMark Brown <broonie@kernel.org>
    259b93b2
max77802-regulator.c 17.7 KB