linux-kernel - Re: [PATCH] of: Add Google Juniper to excluded default cells list

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Message-ID: <CAGXv+5HKCQUNuaeJLdR2O8-VBjpu8ydOcoP0AKP3-__RmrCxRw@mail.gmail.com>
Date: Tue, 26 Nov 2024 11:53:16 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Saravana Kannan <saravanak@...gle.com>, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Sasha Levin <sashal@...nel.org>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Matthias Brugger <matthias.bgg@...il.com>, Conor Dooley <conor@...nel.org>
Subject: Re: [PATCH] of: Add Google Juniper to excluded default cells list

On Mon, Nov 25, 2024 at 11:46 PM Rob Herring <robh@...nel.org> wrote:
>
> On Mon, Nov 25, 2024 at 5:32 AM Krzysztof Kozlowski
> <krzysztof.kozlowski@...aro.org> wrote:
> >
> > Google Juniper platforms have a very old bootloader which populates
> > /firmware node without proper address/size-cells leading to warnings:
> >
> >   Missing '#address-cells' in /firmware
> >   WARNING: CPU: 0 PID: 1 at drivers/of/base.c:106 of_bus_n_addr_cells+0x90/0xf0
> >   Modules linked in:
> >   CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.12.0 #1 933ab9971ff4d5dc58cb378a96f64c7f72e3454d
> >   Hardware name: Google juniper sku16 board (DT)
> >   ...
> >   Missing '#size-cells' in /firmware
> >   WARNING: CPU: 0 PID: 1 at drivers/of/base.c:133 of_bus_n_size_cells+0x90/0xf0
> >   Modules linked in:
> >   CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Tainted: G        W          6.12.0 #1 933ab9971ff4d5dc58cb378a96f64c7f72e3454d
> >   Tainted: [W]=WARN
> >   Hardware name: Google juniper sku16 board (DT)
> >
> > The platform won't receive updated bootloader/firmware so add it to
> > excluded platform list to silence the warning.

Unfortunately this isn't the only platform affected. AFAIK basically any
ARM-based Chromebook out there has the same issue.

> I'm interested to know what needs these in /firmware. /firmware is
> supposed to be for things without an MMIO interface. An alternative
> solution is to add the properties. That doesn't require
> CONFIG_OF_DYNAMIC and is often the approach powerpc uses.

The regs point to a memory region that contains bits left by coreboot,
the coreboot table and the CBMEM region. The latter encompasses the
former, and also includes things such as the coreboot boot log.
These are covered by the binding firmware/coreboot.txt and supported
by drivers under drivers/firmware/google/.

> I'm also wondering if ranges is also missing?

It has an empty "ranges" property. I dug through our repository, and it
looks like the code was added [1] back in the ARMv7 days for the Nyan
(Tegra K1) series of Chromebooks. The code was never updated to use
64-bit addresses.


ChenYu

[1] https://crrev.com/c/203693