Re: [PATCH V6 0/8] drm/exynos: few patches to enhance bridge chip support

From: Thierry Reding <thierry.reding@gmail.com>
To: "Andreas Färber" <afaerber@suse.de>
Cc: devicetree@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
	seanpaul@google.com, daniel.vetter@ffwll.ch, joshi@samsung.com,
	dri-devel@lists.freedesktop.org,
	Doug Anderson <dianders@chromium.org>,
	Javier Martinez Canillas <javier.martinez@collabora.co.uk>,
	Ajay kumar <ajaynumb@gmail.com>,
	prashanth.g@samsung.com, Ajay Kumar <ajaykumar.rs@samsung.com>
Subject: Re: [PATCH V6 0/8] drm/exynos: few patches to enhance bridge chip support
Date: Tue, 29 Jul 2014 13:47:39 +0200	[thread overview]
Message-ID: <20140729114736.GB26346@ulmo.nvidia.com> (raw)
In-Reply-To: <53D78891.4080703@suse.de>

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On Tue, Jul 29, 2014 at 01:42:09PM +0200, Andreas Färber wrote:
> Am 29.07.2014 13:36, schrieb Thierry Reding:
> > On Tue, Jul 29, 2014 at 01:21:48PM +0200, Andreas Färber wrote:
> >> Hi Ajay,
> >>
> >> Am 28.07.2014 08:13, schrieb Ajay kumar:
> >>> On 7/27/14, Andreas Färber <afaerber@suse.de> wrote:
> >>>> Am 25.07.2014 21:22, schrieb Ajay Kumar:
> >>>>> This series is based on exynos-drm-next branch of Inki Dae's tree at:
> >>>>> git://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos.git
> >>>>>
> >>>>> I have tested this after adding few DT changes for exynos5250-snow,
> >>>>> exynos5420-peach-pit and exynos5800-peach-pi boards.
> >>>>
> >>>> I'm trying to test this with a modified exynos5250-spring DT
> [...]
> >> Unfortunately the most I got on Spring with attached DT was a blank
> >> screen with a white horizontal line in the middle.
> >>
> >> Do I need to specify a specific panel model for Spring?
> [...]
> >> From 9172a26a8f0d0f0d170bd27e1c150ad204d8086a Mon Sep 17 00:00:00 2001
> >> From: =?UTF-8?q?Andreas=20F=C3=A4rber?= <afaerber@suse.de>
> >> Date: Sun, 27 Jul 2014 21:58:06 +0200
> >> Subject: [PATCH] ARM: dts: exynos5250: Add eDP/LVDS bridge to Spring
> >> MIME-Version: 1.0
> >> Content-Type: text/plain; charset=UTF-8
> >> Content-Transfer-Encoding: 8bit
> >>
> >> Signed-off-by: Ajay Kumar <ajaykumar.rs@samsung.com>
> >> [AF: Redone for v6]
> >> Signed-off-by: Andreas F??rber <afaerber@suse.de>
> >> ---
> >>  arch/arm/boot/dts/exynos5250-spring.dts | 32 +++++++++++++++++++++++++++++++-
> >>  1 file changed, 31 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/arch/arm/boot/dts/exynos5250-spring.dts b/arch/arm/boot/dts/exynos5250-spring.dts
> >> index 687dfab86bc8..517b1ff2bfdf 100644
> >> --- a/arch/arm/boot/dts/exynos5250-spring.dts
> >> +++ b/arch/arm/boot/dts/exynos5250-spring.dts
> >> @@ -64,10 +64,14 @@
> >>  		vdd_pll-supply = <&s5m_ldo8_reg>;
> >>  	};
> >>  
> >> +	panel: panel {
> >> +		compatible = "simple-panel";
> >> +	};
> > 
> > You can't do this. "simple-panel" isn't a valid panel model. It should
> > probably be removed from the platform_of_match table in the driver.
> 
> Okay, that means the Snow DT is wrong, too:
> https://patchwork.kernel.org/patch/4625441/
> 
> And the others specify it as fallback:
> https://patchwork.kernel.org/patch/4625461/
> https://patchwork.kernel.org/patch/4625451/

A quick grep shows that many (all?) devices that use DRM panels provide
simple-panel as fallback. That's probably fine as long as they also do
provide the specific model. But given that simple-panel does not have a
mode or physical size, I don't think even that makes sense.

Any of the DTS files in the tree I have that list simple-panel as a
fallback are Tegra, so I'll go write a patch that removes the fallback.
I can't think of a reason why it would ever be needed or meaningful.

Thierry

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