linux-kernel - Re: [PATCH v5 3/5] docs: staging: gpio-rpmsg: gpio over rpmsg bus

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Message-ID: <638dac3d-ddcb-4d53-b06d-e0bd3d9077c3@lunn.ch>
Date: Mon, 10 Nov 2025 16:59:27 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Shenwei Wang <shenwei.wang@....com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Jonathan Corbet <corbet@....net>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, Peng Fan <peng.fan@....com>,
	"linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH v5 3/5] docs: staging: gpio-rpmsg: gpio over rpmsg bus

> The remote firmware does not need to know whether Linux is asleep. The GPIO is not used 
> to wake Linux directly; instead, it serves as a wake-up source for the remote firmware if configured 
> accordingly. Once the remote firmware is awake, it sends a notification message to Linux. This 
> notification is the actual event that wakes Linux.
> 
> This works because there is always a physical interface connecting Linux and the remote firmware. 
> On i.MX platforms, this interface is the MU block. When the remoteproc driver is running, the MU 
> block is automatically configured as a wake-up source for Linux by default. As a result, the notification 
> message can wake the Linux system if it is asleep.

You need to add a lot more documentation to the specification to make
this clear. As you said, the firmware and Linux have different
sleep/wake life cycles. How does the firmware know it is safe to go to
sleep, if it has no idea Linux is running or suspended?

	Andrew