linux-kernel - Re: [PATCH] regulator: core: do not ignore repeated requests on stepped regulators

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Message-ID: <6190301.lOV4Wx5bFT@fw-rgant>
Date: Wed, 21 May 2025 13:50:22 +0200
From: Romain Gantois <romain.gantois@...tlin.com>
To: Mark Brown <broonie@...nel.org>
Cc: Liam Girdwood <lgirdwood@...il.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, linux-kernel@...r.kernel.org
Subject:
 Re: [PATCH] regulator: core: do not ignore repeated requests on stepped
 regulators

On Wednesday, 21 May 2025 12:07:05 CEST Mark Brown wrote:
> On Wed, May 21, 2025 at 10:47:24AM +0200, Romain Gantois wrote:
> > Currently, the regulator_set_voltage() function will assume a noop if a
> > consumer requests the same voltage range twice in a row.
> > 
> > This can lead to unexpected behavior if the target regulator has a maximum
> > voltage step constraint. With such constraints, the regulator core may
> > clamp the requested voltage to a lesser value, to ensure that the voltage
> > delta stays under the specified limit.
> 
> No, if there's an issue here we should handle it the first time we set
> the voltage by doing multiple steps in one set_voltage() call.  Having
> individual client drivers all having to repeatedly call set_voltage() is
> obviously not a good API.

Understood, would it make sense to handle this directly in 
regulator_set_voltage_unlocked()?  For example by checking for a max_uV_step 
condition and repeating calls to regulator_do_balance_voltage() until the 
resulting voltage stabilizes?

Thanks,

-- 
Romain Gantois, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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