linux-kernel - Re: [RFC PATCH v1] regulator: pwm-regulator: Fix continuous get

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Date: Fri, 22 Dec 2023 11:53:44 +0000
From: Mark Brown <broonie@...nel.org>
To: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc: Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
	lgirdwood@...il.com, linux-pwm@...r.kernel.org,
	linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Thierry Reding <thierry.reding@...il.com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Dmitry Rokosov <ddrokosov@...rdevices.ru>
Subject: Re: [RFC PATCH v1] regulator: pwm-regulator: Fix continuous
 get_voltage for disabled PWM

On Thu, Dec 21, 2023 at 11:07:41PM +0100, Uwe Kleine-König wrote:
> On Thu, Dec 21, 2023 at 09:45:49PM +0000, Mark Brown wrote:

> > > -       voltage = pwm_get_relative_duty_cycle(&pstate, duty_unit);
> > > +       if (pstate.enabled)
> > > +               voltage = pwm_get_relative_duty_cycle(&pstate, duty_unit);
> > > +       else if (max_uV_duty < min_uV_duty)
> > > +               voltage = max_uV_duty;
> > > +       else
> > > +               voltage = min_uV_duty;

> > AFAICT this means that enabling the PWM changes the voltage read back
> > which isn't what we expect (other than a change from 0 to target) and is
> > likely to cause issues.  get_voltage() should not change after an
> > enable(), and indeed I'm unclear how this change works?  I'd expect a
> > change in the init_state() function, possibly one that programs the PWM
> > to reflect the actual hardware state but I'm not 100% confident on that
> > without digging into the PWM API more.

> What is your question here? Looking at pwm_regulator_set_voltage() I
> think this lacks a

> 	pstate.enabled = true;

> which might also fix Martin's problem?

That's not really a question, it's a statement - I don't see how the
change works at all and as it stands it introduces a problem with the
behaviour when the regulator is enabled.

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