[PATCH 1/2] ARM: tegra: add Acer Chromebook 13 device tree

Olof Johansson olof at lixom.net
Wed Aug 13 10:37:15 PDT 2014

On Wed, Aug 13, 2014 at 10:31 AM, Stephen Warren <swarren at wwwdotorg.org> wrote:
> On 08/13/2014 11:23 AM, Olof Johansson wrote:
>> On Wed, Aug 13, 2014 at 10:10 AM, Stephen Warren <swarren at wwwdotorg.org>
>> wrote:
>>> On 08/12/2014 07:56 PM, Dylan Reid wrote:
>>>> The Acer Chromebook 13, codenamed "Big", contains an NVIDIA tegra124
>>>> processor and is similar to the Venice2 reference platform.
>>>> The keyboard, USB 2, audio, HDMI, sdcard and emmc have been tested
>>>> and work on the 1366x768 models.  I haven't tried on the HD systems
>>>> yet.
>>>> WiFi does not yet work, it needs at least some PMIC changes to enable
>>>> the 32k clock.
>>>> The elan trackpad is not yet functional but hopefully will be soon as
>>>> there are patches under review.
>>>> There is also an issue on reboot because the TPM isn't reset.  It will
>>>> cause the stock firmware to enter recovery mode.  This can be worked
>>>> around by an EC-reset, press refresh and power at the same time.
>>>> diff --git a/arch/arm/boot/dts/tegra124-big.dts
>>>> b/arch/arm/boot/dts/tegra124-big.dts
>>> I think we need to include the SKU name in the filename and compatible
>>> value
>>> below, or at least plan out that for other SKUs, we'll add the SKU name
>>> on.
>>>> +/ {
>>>> +       model = "Google Big";
>>>> +       compatible = "google,nyan-big", "nvidia,tegra124";
>>> I think it'd be more user-friendly if the filename and compatible value
>>> more
>>> obviously tied to the end-user-visible product name.
>> We didn't prefix the reference platform on the very first one we
>> shipped (snow), but for the peach platforms we used peach-pit and
>> peach-pi. Those had different SoCs inside (albeit very similar ones),
>> so there was a reason for separate DTS files.
>> Here, we should probably prefix with nyan (so tegra124-nyan-big.dts).
>> Users have shown themselves to be quite happy to use the internal
>> names, they also tend to be less confusing (since we can't rely on the
>> vendor to rename the product when the internals change, so we would
>> need a separate namespace anyway).
> I can see that the vendor might change the internals without changing the
> product name. That kind of thing happens too frequently across all kinds of
> products. So, there are certainly disadvantages using consumer marketing
> names here.
> Presumably though the name "big" would no longer apply to any modified HW?
> Hence, I can't understand the need to say "nyan-big" rather than just "big".
> Is "nyan-" really needed to fully qualify the name? Also, the board isn't a
> Nyan, albeit the design may have been strongly derived from the reference
> board named Nyan.

it's more about partitioning the namespace and showing similarities
(nyan-big and nyan-foo might be able to share a common dtsi for most
of the platform, for example).

See https://chromium.googlesource.com/chromiumos/third_party/kernel-next/+/chromeos-3.10/arch/arm/boot/dts/
for how it's done in the product tree (some of those bindings are of
course divergent from upstream, so it's more about the file structure
in this case).

It's a model that's working pretty well for us w.r.t
sharing/inheriting/expanding dts contents. If you have a better idea
we'd be willing to consider it, of course.


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