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

From: Ajay kumar <ajaynumb@gmail.com>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: "Doug Anderson" <dianders@chromium.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-samsung-soc@vger.kernel.org"
	<linux-samsung-soc@vger.kernel.org>,
	"Sean Paul" <seanpaul@google.com>,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"sunil joshi" <joshi@samsung.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"Ajay Kumar" <ajaykumar.rs@samsung.com>,
	"Javier Martinez Canillas" <javier.martinez@collabora.co.uk>,
	"Prashanth G" <prashanth.g@samsung.com>,
	"Andreas Färber" <afaerber@suse.de>
Subject: Re: [PATCH V6 0/8] drm/exynos: few patches to enhance bridge chip support
Date: Wed, 30 Jul 2014 11:54:00 +0530	[thread overview]
Message-ID: <CAEC9eQOpmUsZKEJ_uK7Y73kn9Q5Rk8=n3jV9orBYwn2R4M0efA@mail.gmail.com> (raw)
In-Reply-To: <20140729114736.GB26346@ulmo.nvidia.com>

Hi Thierry,

On Tue, Jul 29, 2014 at 5:17 PM, Thierry Reding
<thierry.reding@gmail.com> wrote:
> 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.
On snow, the bridge chip provides the display mode instead of the panel.
That is why display was working for me.

> 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.
Ok. I will resend DT patches removing "simple-panel" fallback.

Regards,
Ajay
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