linux-kernel - Re: [PATCH 4/5] regulator: pwm: Add support for voltage linear equal steps

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Date:	Mon, 14 Mar 2016 16:28:43 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Laxman Dewangan <ldewangan@...dia.com>
Cc:	robh+dt@...nel.org, pawel.moll@....com, lgirdwood@...il.com,
	lee.jones@...aro.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] regulator: pwm: Add support for voltage linear equal
 steps

On Sun, Mar 13, 2016 at 06:36:06PM +0530, Laxman Dewangan wrote:
> On Saturday 12 March 2016 11:39 AM, Mark Brown wrote:

> >I can't see any reason why this would ever be preferable to just using
> >the flat linear range (you certainly haven't articulated one, you're
> >just stating it).  This seems like you are bodging around a limited
> >consumer driver, you should fix the consumer to cope with regulators
> >with lots of voltages - PWM regulators aren't the only ones with high
> >resolution steps.

> The requirement is to have perfect linear steps interms of the period/pulse
> time of PWM without loosing any voltage.
> Continuous mode is pretty much near to what you said but here we are loosing
> the perfect step as this divides the periods to 100 parts and then set
> voltage.

Could you be more specific about what the issue is?  We've hopefully got
errors of less than 1% in the values here...

> If new mode is not accpetable then need to enhance the existing continuous
> mode like before scaling for 100% of period, first look if we get the
> perfect pulse time of of PWM period and if it is there then use this direct
> instead of converting required voltage to 100% scale and then back
> calculating duty time.

That seems a lot better, what you're proposing is changing the ABI to
fudge things for a client specific requirement where both the client
requirement and the change you're proposing are specific to the current
Linux implementation.  That doesn't sound like a DT thing.

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