linux-kernel - Re: [PATCH v2 00/13] regulator: pwm: various improvements

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Date:	Thu, 09 Jun 2016 20:04:20 +0200
From:	Heiko Stübner <heiko@...ech.de>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Thierry Reding <thierry.reding@...il.com>,
	linux-pwm@...r.kernel.org, Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	linux-rockchip@...ts.infradead.org,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Milo Kim <milo.kim@...com>,
	Doug Anderson <dianders@...gle.com>,
	Caesar Wang <wxt@...k-chips.com>,
	Stephen Barber <smbarber@...omium.org>,
	Brian Norris <briannorris@...omium.org>,
	Ajit Pal Singh <ajitpal.singh@...com>,
	Srinivas Kandagatla <srinivas.kandagatla@...il.com>,
	Maxime Coquelin <maxime.coquelin@...com>,
	Patrice Chotard <patrice.chotard@...com>, kernel@...inux.com,
	Laxman Dewangan <ldewangan@...dia.com>
Subject: Re: [PATCH v2 00/13] regulator: pwm: various improvements

Hi Boris,

Am Mittwoch, 8. Juni 2016, 18:34:35 schrieb Boris Brezillon:
> This patch series series aims at adding two important features to the
> pwm-regulator driver.
> 
> The first one is the support for 'smooth handover' between the
> bootloader and the kernel. This is mainly solving problems we have when
> the PWM is controlling a critical regulator (like the one powering the
> DDR chip). Currently, when the PWM regulator acquire the PWM device it
> assumes it was off and it's safe to change the configuration before
> enabling it, which can generate glitches on the PWM signal which in turn
> generated glitches on the output voltage.
> To solve that we've introduced support for hardware readout to the
> PWM framework, so that the PWM regulator driver can adjust the PWM
> a probe time and avoid glitches.
> Atomic update is also helping in this regard.

[...]

> The second feature we add to the driver is the capability of using
> a sub duty_cycle range in continuous mode. By default the regulator
> is assuming that min_uV is achieved with a 0% dutycyle and max_uV
> with a 100% dutycycle, but this is not necessarily true.
> Moreover, in some cases (when the PWM device does not support
> polarity inversion), we might have min_uV at 100% and max_uV at 0%.
> Hence the addition of new properties to the existing DT bindings.
> The feature is added in patch 12 and 13.

I've tested this series on a rk3288-veyron chromebook and both the backlight-
pwm as well as the pwm-regulator still work as expected, so for everything 
except the STI parts:

Tested-by: Heiko Stuebner <heiko@...ech.de>