On Wed, Jul 30, 2014 at 11:54:00AM +0530, Ajay kumar wrote: > Hi Thierry, > > On Tue, Jul 29, 2014 at 5:17 PM, Thierry Reding > <thierry.reding@xxxxxxxxx> 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@xxxxxxx> 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@xxxxxxx> > >> >> 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@xxxxxxxxxxx> > >> >> [AF: Redone for v6] > >> >> Signed-off-by: Andreas F??rber <afaerber@xxxxxxx> > >> >> --- > >> >> 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. Okay, I suppose under some circumstances that might make sense. Although it's still always the panel that dictates the display timings, so the panel node needs to have a panel model specific compatible value with a matching entry in the panel-simple driver so that it can even be used in setups without a bridge. One other thing: how does the bridge know which mode to drive? I suspect that it can drive more than one mode? Can it freely be configured or does it have a predefined set of modes? If the latter, then according to what you said above there needs to be a way to configure the bridge (via DT?) so that it reports the mode matching the panel. I wonder if that should be handled completely in code, so that for example a bridge has a panel attached it can use the panel's .get_modes() and select a matching mode among the set that it supports. Thierry
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