linux-kernel - Re: [PATCH v1 2/6] arm: arm64: dts: Enable cros-ec-spi as wake source

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Date: Thu, 14 Dec 2023 16:20:27 -0600
From: Rob Herring <robh@...nel.org>
To: Mark Hasemeyer <markhas@...omium.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Raul Rangel <rrangel@...omium.org>, 
	Alim Akhtar <alim.akhtar@...sung.com>, Andre Przywara <andre.przywara@....com>, 
	Andy Gross <agross@...nel.org>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Baruch Siach <baruch@...s.co.il>, 
	Bjorn Andersson <andersson@...nel.org>, Claudiu Beznea <claudiu.beznea@...rochip.com>, 
	Conor Dooley <conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>, 
	Jesper Nilsson <jesper.nilsson@...s.com>, Jisheng Zhang <jszhang@...nel.org>, 
	Jonathan Hunter <jonathanh@...dia.com>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
	Matthias Brugger <matthias.bgg@...il.com>, Michal Simek <michal.simek@....com>, 
	Paul Barker <paul.barker@...cloud.com>, Sudeep Holla <sudeep.holla@....com>, 
	Thierry Reding <thierry.reding@...il.com>, cros-qcom-dts-watchers@...omium.org, 
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-arm-msm@...r.kernel.org, linux-mediatek@...ts.infradead.org, 
	linux-rockchip@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
	linux-tegra@...r.kernel.org
Subject: Re: [PATCH v1 2/6] arm: arm64: dts: Enable cros-ec-spi as wake source

On Thu, Dec 14, 2023 at 3:04 PM Mark Hasemeyer <markhas@...omium.org> wrote:
>
> > If a device knows it is wakeup capable, why do you need a property too?
>
> I'm referencing:
> https://www.kernel.org/doc/Documentation/devicetree/bindings/power/wakeup-source.txt
> "Nodes that describe devices which has wakeup capability must contain
> an "wakeup-source" boolean property."

That's probably too strongly worded because wakeup capable devices
existed (and still exist) before this binding was created. Powerpc for
example doesn't use it.

> Currently the driver assumes the device is wake capable without
> parsing the device tree, which is an incorrect assumption as wake
> capability should not be enabled on some cros_ec systems.
>
> > I haven't looked closely enough, but it smells like after patch 6, these
> > properties would be required for wakeup? That would be an ABI break.
>
> Agreed. In this case, the driver is a ChromeOS related driver and DTS
> is built from source for each OS update.
> For more context, I will make sure to CC you (and everyone else) and
> include a cover letter in the next series version.

Please explain in the patches with an ABI break why it doesn't matter.

Rob