linux-kernel - Re: [PATCH v2 1/1] hwmon: (pmbus) Add regulator supply into macro

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Date:   Fri, 4 Nov 2022 15:30:30 -0700
From:   Zev Weiss <zev@...ilderbeest.net>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Marcello Sylvester Bauer <sylv@...v.io>,
        Jean Delvare <jdelvare@...e.com>, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org,
        Patrick Rudolph <patrick.rudolph@...ements.com>
Subject: Re: [PATCH v2 1/1] hwmon: (pmbus) Add regulator supply into macro

On Tue, Feb 22, 2022 at 08:51:04AM PST, Guenter Roeck wrote:
>On Mon, Feb 21, 2022 at 12:09:56PM +0100, Marcello Sylvester Bauer wrote:
>> Add regulator supply into PWBUS_REGULATOR macro. This makes it optional
>> to define a vin-supply in DT. Not defining a supply will add a dummy
>> regulator supply instead and only cause the following debug output:
>>
>> ```
>> Looking up vin-supply property in node [...] failed
>> ```
>>
>> Signed-off-by: Marcello Sylvester Bauer <sylv@...v.io>
>
>Applied to hwmon-next. That should give it some time to mature,
>and we can pull or modify it if it causes any problems.
>

Wish I'd caught this sooner, but unfortunately I've just discovered that 
this does in fact cause breakage on my systems -- having regulator-dummy 
set as a supply on my PMBus regulators (instead of having them as their 
own top-level regulators without an upstream supply) leads to 
enable-count underflow errors when disabling them:

     # echo 0 > /sys/bus/platform/devices/efuse01/state
     [  906.094477] regulator-dummy: Underflow of regulator enable count
     [  906.100563] Failed to disable vout: -EINVAL
     [  136.992676] reg-userspace-consumer efuse01: Failed to configure state: -22

A simple revert solves the problem for me, but since I'm honestly a 
little unclear on the intent of the patch itself I'm not sure what a 
revert might break and hence I don't know if that's necessarily the 
right fix.  Marcello (or others), any thoughts?


Thanks,
Zev