linux-kernel - Re: [PATCH] regulator: core: Allow for regulators that can't be read at bootup

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Message-ID: <4547e1cb-a39c-decd-9384-4e2c6d28f64d@codeaurora.org>
Date:   Wed, 16 May 2018 15:47:22 -0700
From:   David Collins <collinsd@...eaurora.org>
To:     Douglas Anderson <dianders@...omium.org>, broonie@...nel.org
Cc:     mka@...omium.org, Liam Girdwood <lgirdwood@...il.com>,
        linux-kernel@...r.kernel.org,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH] regulator: core: Allow for regulators that can't be read
 at bootup

On 05/15/2018 03:07 PM, Douglas Anderson wrote:
> 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.

This problem specifically arises in the latest RPMh regulator patch [1] if
regulator-min-microvolt and regulator-max-microvolt are specified for a
VRM managed RPMh regulator device but the qcom,regulator-initial-microvolt
property is not provided.  Therefore, listing
qcom,regulator-initial-microvolt is a way to avoid regulator registration
issues.


> In this patch I propose the error code -ENOTRECOVERABLE.  In errno.h
> this error is described as "State not recoverable".

I'm fine with this constant.  Hopefully Mark is as well.


> If this patch is accepted then we'll need to update the latest RPMh
> regulator patch to return it.  The current patch returns -EINVAL which
> means that the regulator always fails.

I'll make this modification if needed.

Take care,
David

[1] https://lkml.org/lkml/2018/5/11/703

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