linux-kernel - Re: [PATCH] pmdomain: arm: scmi_pm

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Message-ID: <Z4TreQ5bA9qiMTgC@bogus>
Date: Mon, 13 Jan 2025 10:31:21 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: "Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc: <cristian.marussi@....com>, <ulf.hansson@...aro.org>,
	Sudeep Holla <sudeep.holla@....com>, <arm-scmi@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-pm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <ranjani.vaidyanathan@....com>,
	Peng Fan <peng.fan@....com>
Subject: Re: [PATCH] pmdomain: arm: scmi_pm_domain: Initialize state as off

On Fri, Jan 10, 2025 at 02:13:46PM +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@....com>
> 
> Per ARM SCMI Spec DEN0056E, page 16, "The platform may disable a resource
> if no agent has requested to use that resource."
>

True, but ...

> Linux Kernel should not rely on a state that it has not requested, so
> make state as off during initialization.
>

IIUC, this was done to avoid any transitions if the bootloader like U-Boot
has turned on the resource and OS can just rely on that stay. Anyways if
the resource is not used by any driver/device in the kernel, won't it be
turned off anyways ? What am I missing ?

I need to dig details, but I remember doing what this patch does and
reverting to what we have based on the feedback IIRC.

--
Regards,
Sudeep