linux-kernel - Re: drm/radeon/kms: fix up LVDS handling on macs (v2)

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Message-ID: <1263526556.724.402.camel@pasglop>
Date:	Fri, 15 Jan 2010 14:35:56 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Michel Dänzer <michel@...nzer.net>
Cc:	Alex Deucher <alexdeucher@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dave Airlie <airlied@...hat.com>
Subject: Re: drm/radeon/kms: fix up LVDS handling on macs (v2)

On Thu, 2010-01-14 at 11:09 +0100, Michel Dänzer wrote:
> I have looked at radeonfb for a patch I posted a while ago to expose a
> backlight class device with KMS, and I can only see what you describe
> above affecting the LVDS_GEN_CNTL backlight level, not BLON or
> BL_MOD_EN. Am I missing something?

No, you aren't, it's radeonfb who is :-) I never quite got that part
right. I was somewhat hoping several times that Hui and then Alex would
manage to dig some info from ATI about what the right method is to drive
those panels I think :-)

But my observation on those HW was definitely that when inverted,
disabling the modulation was also turning the panel to full bright on,
rather than turning it off.

> Without my patch, KMS doesn't change the backlight level at all, so
> assuming the firmware manages to enable the backlight, it should stay
> like that.

Your patch might make things better than they are today, I'm not arguing
there :-) I'm just saying that now might be a good time to try to sort
out exactly what should be done in there :-)

Cheers,
Ben.

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