linux-kernel - Re: [PATCH v6 1/4] Runtime Interpreted Power Sequences

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Message-ID: <1464760.6eqxJ2IzZ2@percival>
Date:	Thu, 13 Sep 2012 15:08:23 +0900
From:	Alex Courbot <acourbot@...dia.com>
To:	Tomi Valkeinen <tomi.valkeinen@...com>
CC:	Stephen Warren <swarren@...dia.com>,
	Thierry Reding <thierry.reding@...onic-design.de>,
	Simon Glass <sjg@...omium.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Anton Vorontsov <cbou@...l.ru>,
	David Woodhouse <dwmw2@...radead.org>,
	Arnd Bergmann <arnd@...db.de>,
	Leela Krishna Amudala <l.krishna@...sung.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v6 1/4] Runtime Interpreted Power Sequences

On Thursday 13 September 2012 13:45:39 Tomi Valkeinen wrote:
> * PGP Signed by an unknown key
> 
> On Wed, 2012-09-12 at 18:57 +0900, Alexandre Courbot wrote:
> 
> > Some device drivers (panel backlights especially) need to follow precise
> > sequences for powering on and off, involving gpios, regulators, PWMs
> > with a precise powering order and delays to respect between each steps.
> > These sequences are board-specific, and do not belong to a particular
> > driver - therefore they have been performed by board-specific hook
> > functions to far.
> 
> 
> The sequences are not board-specific, they are device (backlight, etc.)
> specific. The sequences have been handled in board-specific hook
> functions so far because there hasn't been proper drivers for the
> devices.
> 
> If I were to take the same panel (and backlight) you have and install it
> on my board, I would need the same power sequence.

You could also have power sequences that control a set of GPIOs for an 
external interface (and would then be more board-specific), but you are right 
that for most of the case power seqs apply to devices and this statement is 
misleading. I will fix that in the commit message and wherever this might 
appear.

Alex.

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