linux-kernel - Re: [PATCH 1/4] ARM: tegra: rely on bootloader pinmux programming on nyan-big

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Date:	Tue, 6 Jan 2015 19:37:04 -0800
From:	Andrew Bresticker <abrestic@...omium.org>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] ARM: tegra: rely on bootloader pinmux programming on nyan-big

On Tue, Jan 6, 2015 at 9:09 AM, Stephen Warren <swarren@...dotorg.org> wrote:
> On 01/06/2015 03:37 AM, Tomeu Vizoso wrote:
>>
>> Following 6dbaff2b, the kernel expects that the bootloader has correctly
>> programmed the Tegra pinmux.
>>
>> DTs for the Jetson and the Venice2 had been updated already but this one
>> was left behind.
>
>
> So this setup is true for NVIDIA-controlled development/reference boards
> where we've ensured that the bootloader sets up 100% of the pinmux.
>
> However, I know that Coreboot on this board doesn't set up everything in the
> pinmux, and since it's in r/o flash never will. As such, I'm not sure this
> change is safe for this board. That is, unless you want to force upstream
> kernels to be booted via a chain-loaded path: Coreboot (r/o) -> U-Boot (r/w
> with full pinmux setup) -> kernel.

That's correct.  We did have a patch floating around to configure all
the pinmux settings in coreboot, but that never made it in.  While we
could issue a R/W firmware update to apply the pinmux settings
(unlikely to happen), it would still result in pinmux settings being
applied in two separate locations - which, IIRC, was exactly what
Stephen was trying to avoid by moving pinmux out of the device-trees.
So I'd agree that pulling the pinmux settings out of the nyan*
device-trees is not a good idea.
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