linux-kernel - Re: [PATCH] backlight: lcd: add driver for raster-type lcd's with gpio controlled panel reset

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Message-ID: <CAJuYYwR6tySTcD9RdNcuGhqCRT2mSLep2sMf1MOJViXEbFEwxw@mail.gmail.com>
Date:	Wed, 11 Jan 2012 16:28:53 +0530
From:	Thomas Abraham <thomas.abraham@...aro.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kgene.kim@...sung.com, lars@...afoo.de, kwangwoo.lee@...il.com,
	patches@...aro.org, jg1.han@...sung.com, rob.herring@...xeda.com,
	grant.likely@...retlab.ca, cbou@...l.ru, kyungmin.park@...sung.com,
	linux-samsung-soc@...r.kernel.org, rpurdie@...ys.net,
	ben-linux@...ff.org, broonie@...nsource.wolfsonmicro.com,
	augulis.darius@...il.com
Subject: Re: [PATCH] backlight: lcd: add driver for raster-type lcd's with
 gpio controlled panel reset

Hi Russell,

On 7 January 2012 23:53, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Thu, Jan 05, 2012 at 09:12:26PM +0530, Thomas Abraham wrote:
>> Add a lcd panel driver for simple raster-type lcd's which uses a gpio
>> controlled panel reset. The driver controls the nRESET line of the panel
>> using a gpio connected from the host system. The Vcc supply to the panel
>> is (optionally) controlled using a voltage regulator. This driver excludes
>> support for lcd panels that use a serial command interface or direct
>> memory mapped IO interface.
>
> I'm trying to work out what kind of LCD panel this is for.  I assume
> not the panels which would be connected to a SoC, which have a parallel
> interface to a frame buffer device (LCD controller)?
>
> If this is for these kinds of LCD panels, how are you handling the
> timing required for active panels - some of which must not be powered
> up without the LCD controller first being setup and enabled, and must
> be powered down before the LCD controller is disabled.
>
> I've seen this requirement with panels connected to ARM Ltd's development
> boards, and also some SoCs.

This patch is for passive panels that use a nRESET line controlled by
a SoC GPIO and the panel do not use serial command interface (i2c or
spi) or memory-mapped-io for panel control. Panels that just need a
nRESET to be controlled can be handled by this driver.

Thanks,
Thomas.
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