From 84b3a7c9c6befe5ab4d49070fe7bcab2da22637e Mon Sep 17 00:00:00 2001 From: Douglas Anderson Date: Tue, 15 May 2018 15:07:17 -0700 Subject: regulator: core: Allow for regulators that can't be read at bootup Regulators attached via RPMh on Qualcomm sdm845 apparently are write-only. Specifically you can send a request for a certain voltage but you can't read back to see what voltage you've requested. What this means is that at bootup we have absolutely no idea what voltage we could be at. As discussed in the patches to try to support the RPMh regulators [1], the fact that regulators are write-only means that its driver's get_voltage_sel() should return an error code if it's called before any calls to set_voltage_sel(). This causes problems in machine_constraints_voltage() when trying to apply the constraints. A proposed fix was to come up with an error code that could be returned by get_voltage_sel() which would cause the regulator framework to simply try setting the voltage with the current constraints. In this patch I propose the error code -ENOTRECOVERABLE. In errno.h this error is described as "State not recoverable". Though the error code was originally intended "for robust mutexes", the description of the error code seems to apply here because we can't read the state of the regulator. Also note that the only existing user of this error code in the regulator framework is tps65090-regulator.c which returns this error code from the enable() call (not get_voltage() or get_voltage_sel()), so there should be no existing regulators that might accidentally get the new behavior. (Side note is that tps65090 seems to interpret this error code to mean an error that you can't recover from rather than some data that can't be recovered). [1] https://patchwork.kernel.org/patch/10340897/ Signed-off-by: Douglas Anderson Signed-off-by: Mark Brown --- include/linux/regulator/driver.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'include/linux/regulator') diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h index 4fc96cb8e5d7..14e512ad6d4f 100644 --- a/include/linux/regulator/driver.h +++ b/include/linux/regulator/driver.h @@ -81,9 +81,12 @@ struct regulator_linear_range { * @set_voltage_sel: Set the voltage for the regulator using the specified * selector. * @map_voltage: Convert a voltage into a selector - * @get_voltage: Return the currently configured voltage for the regulator. + * @get_voltage: Return the currently configured voltage for the regulator; + * return -ENOTRECOVERABLE if regulator can't be read at + * bootup and hasn't been set yet. * @get_voltage_sel: Return the currently configured voltage selector for the - * regulator. + * regulator; return -ENOTRECOVERABLE if regulator can't + * be read at bootup and hasn't been set yet. * @list_voltage: Return one of the supported voltages, in microvolts; zero * if the selector indicates a voltage that is unusable on this system; * or negative errno. Selectors range from zero to one less than -- cgit v1.2.3-59-g8ed1b