Re: [PATCHv13][ 2/4] video: imxfb: Also add pwmr for the device tree.

[Alexander Shiyan]

> On Thu, Dec 05, 2013 at 04:43:37PM +0100, Denis Carikli wrote:
> > pwmr has to be set to get the imxfb backlight work,
> > though pwmr was only configurable trough the platform data.
> > 
> > Cc: Rob Herring <rob.herring at calxeda.com>
> > Cc: Pawel Moll <pawel.moll at arm.com>
> > Cc: Mark Rutland <mark.rutland at arm.com>
> > Cc: Stephen Warren <swarren at wwwdotorg.org>
> > Cc: Ian Campbell <ijc+devicetree at hellion.org.uk>
> > Cc: devicetree at vger.kernel.org
> > Cc: Jean-Christophe Plagniol-Villard <plagnioj at jcrosoft.com>
> > Cc: Tomi Valkeinen <tomi.valkeinen at ti.com>
> > Cc: linux-fbdev at vger.kernel.org
> > Cc: Sascha Hauer <kernel at pengutronix.de>
> > Cc: linux-arm-kernel at lists.infradead.org
> > Cc: Eric Bénard <eric at eukrea.com>
> > Signed-off-by: Denis Carikli <denis at eukrea.com>
> > Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj at jcrosoft.com>
> > Acked-by: Grant Likely <grant.likely at linaro.org>
> > ---
> >  .../devicetree/bindings/video/fsl,imx-fb.txt       |    3 +++
> >  drivers/video/imxfb.c                              |    2 ++
> >  2 files changed, 5 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/video/fsl,imx-fb.txt b/Documentation/devicetree/bindings/video/fsl,imx-fb.txt
> > index 46da08d..ac457ae 100644
> > --- a/Documentation/devicetree/bindings/video/fsl,imx-fb.txt
> > +++ b/Documentation/devicetree/bindings/video/fsl,imx-fb.txt
> > @@ -17,6 +17,9 @@ Required nodes:
> >  Optional properties:
> >  - fsl,dmacr: DMA Control Register value. This is optional. By default, the
> >  	register is not modified as recommended by the datasheet.
> > +- fsl,pwmr:  LCDC PWM Contrast Control Register value. That property is
> > +	optional, but defining it is necessary to get the backlight working. If that
> > +	property is ommited, the register is zeroed.
> 
> Why isn't this implemented as a backlight driver? Static devicetree
> provided values is very limiting.

Let's understand the terminology.
This register should be renamed according to the datasheet, i.e. LPCCR.
As I pointed out earlier, it is NOT control the backlight, this is a contrast control.
Yes, it works as PWM, but nothing do with the backlight subsystem.
Yes, we can make a driver for this PWM, but how are we going to control it?
I misunderstood something?

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