linux-kernel - Re: [PATCH v2] regulator: pwm: Fix regulator ramp delay for continuous mode

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Date:	Thu, 7 Jul 2016 14:06:23 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Douglas Anderson <dianders@...omium.org>,
	Mark Brown <broonie@...nel.org>
CC:	<boris.brezillon@...e-electrons.com>, <lee.jones@...aro.org>,
	<briannorris@...omium.org>, <linux-rockchip@...ts.infradead.org>,
	"Heiko Stuebner" <heiko@...ech.de>, <thierry.reding@...il.com>,
	<lgirdwood@...il.com>, <linux-kernel@...r.kernel.org>,
	<afrid@...dia.com>
Subject: Re: [PATCH v2] regulator: pwm: Fix regulator ramp delay for continuous
 mode


On Thursday 07 July 2016 12:12 AM, Douglas Anderson wrote:
> The original commit adding support for continuous voltage mode didn't
> handle the regulator ramp delay properly.  It treated the delay as a
> fixed delay in uS despite the property being defined as uV / uS.  Let's
> adjust it.  Luckily there appear to be no users of this ramp delay for
> PWM regulators (as per grepping through device trees in linuxnext).
>
> Note also that the upper bound of usleep_range probably shouldn't be a
> full 1 ms longer than the lower bound since I've seen plenty of hardware
> with a ramp rate of ~5000 uS / uV and for small jumps the total delays
> are in the tens of uS.  1000 is way too much.  We'll try to be dynamic
> and use 10%.
>
> NOTE: This commit doesn't add support for regulator-enable-ramp-delay.
> That could be done in a future patch when someone has a user of that
> featre.
>
> Though this patch is shows as "fixing" a bug, there are no actual known
> users of continuous mode PWM regulator w/ ramp delay in mainline and so
> this likely won't have any effect on anyone unless they are working
> out-of-tree with private patches.  For anyone in this state, it is
> highly encouraged to also pick Boris Brezillon's WIP patches to get
> yourself a reliable and glitch-free regulator.
>
> Fixes: 4773be185a0f ("regulator: pwm-regulator: Add support for continuous-voltage")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>


Looks fine here.
Acked-by: Laxman Dewangan <ldewangan@...dia.com>

BTW, for some PWM regulator, the settling time for voltage change is 
same for any steps.