Devices which may take a while to initialize during probe and which have no strong reason to probe synchronously can request asynchronous probing as default probe strategy. This can speed-up start times on some platforms. The BU27008 gets probe delayed for at least two reasons. It enables the supply regulator, (which is likely to have ramp-up delay if it was disabled) and additionally it delays while the sensor itself is initializing. Changing to asynchronous probing may cause problems. Some of which are discussed in: https://lore.kernel.org/all/06db017f-e985-4434-8d1d-02ca2100cca0@xxxxxxxxxxxxx/ Enabling async probing for the ROHM BU27008 should be fairly safe to try though as there is no in-tree users for it yet. If the async probing appears to be an issue we can switch easily back to synchronous (or better yet, fix the actual problem). Enable asynchronous probing for BU27008. Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx> --- I am unsure if this change is 100% safe - but I don't immediately see the harm. Please let me know if some of you have more experience on problems when using asynchronous probing with IIO devices. --- drivers/iio/light/rohm-bu27008.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/iio/light/rohm-bu27008.c b/drivers/iio/light/rohm-bu27008.c index c04d845062ba..628d17036bb4 100644 --- a/drivers/iio/light/rohm-bu27008.c +++ b/drivers/iio/light/rohm-bu27008.c @@ -982,6 +982,7 @@ static struct i2c_driver bu27008_i2c_driver = { .driver = { .name = "bu27008", .of_match_table = bu27008_of_match, + .probe_type = PROBE_PREFER_ASYNCHRONOUS, }, .probe_new = bu27008_probe, }; -- 2.40.0 -- Matti Vaittinen, Linux device drivers ROHM Semiconductors, Finland SWDC Kiviharjunlenkki 1E 90220 OULU FINLAND ~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~ Simon says - in Latin please. ~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~ Thanks to Simon Glass for the translation =]
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