linux-kernel - Re: [PATCH 4/4] ARM: tegra: roth: add display DT node

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Date:	Mon, 21 Jul 2014 09:35:27 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Alexandre Courbot <acourbot@...dia.com>,
	Thierry Reding <thierry.reding@...il.com>
CC:	Terje Bergstrom <tbergstrom@...dia.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] ARM: tegra: roth: add display DT node

On 07/02/2014 09:10 PM, Alexandre Courbot wrote:
> On 07/03/2014 12:55 AM, Stephen Warren wrote:
>> On 07/02/2014 06:19 AM, Alexandre Courbot wrote:
>>> DSI support has been fixed to support continuous clock behavior that the
>>> panel used on SHIELD requires, so finally add its device tree node since
>>> it is functional.
>>
>>> diff --git a/arch/arm/boot/dts/tegra114-roth.dts
>>> b/arch/arm/boot/dts/tegra114-roth.dts
>>
>>> +    host1x@...00000 {
>>> +        dsi@...00000 {
>>
>> That node looks fine, but I wonder why we need to mark a bunch of
>> regulators as always-on? shouldn't the references to vdd-supply and
>> power-supply from this node be enough? If not, perhaps the tree
>> structure of the regulators isn't correct, or the DSI or panel bindings
>> don't allow enough regulators to be referenced?
> 
> regulator-always-on is indeed not needed for vdd_lcd. I actually had a
> patch in my tree removing this line that I forgot to squash. Will post a
> v2 for this patch that fixes this, thanks.
> 
> vdd-2v8-display needs to remain always-on however. Here we may hit a
> limitation of the simple-panel driver, where only one power supply can
> be provided.

Can't we fix the simple-panel driver to allow a list of regulators in
the property?

I suppose that this technique is OK though; we can always simplify the
DT later if the simple-panel binding gets enhanced.
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