linux-kernel - Re: [PATCH 2/2] firmware: arm_scmi: power_control: Set SCMI_SYSPOWER

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Message-ID: <20250624-agile-moth-of-blizzard-c7babf@sudeepholla>
Date: Tue, 24 Jun 2025 11:21:52 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Peng Fan <peng.fan@....com>
Cc: "Peng Fan (OSS)" <peng.fan@....nxp.com>, Dhruva Gole <d-gole@...com>,
	Cristian Marussi <cristian.marussi@....com>,
	"arm-scmi@...r.kernel.org" <arm-scmi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sudeep Holla <sudeep.holla@....com>,
	Ranjani Vaidyanathan <ranjani.vaidyanathan@....com>,
	Chuck Cannon <chuck.cannon@....com>
Subject: Re: [PATCH 2/2] firmware: arm_scmi: power_control: Set
 SCMI_SYSPOWER_IDLE in pm resume

On Tue, Jun 24, 2025 at 01:23:10AM +0000, Peng Fan wrote:
> > 
> > Just to summarise my understanding here at very high level, the issue
> > exists as the second notification by an agent to the Linux to suspend
> > the system wakes up the system from suspend state. Since the
> > interrupts are enabled before the thaw_processes() (which eventually
> > continues the execution of scmi_suspend_work_func() to set the state
> > to SCMI_SYSPOWER_IDLE, the scmi_userspace_notifier() is executed
> > much before and ends up ignoring the request as the state is still not
> > set to SCMI_SYSPOWER_IDLE. There is a race which your patch is
> > addressing.
> 
> Thanks for writing this down, It is very correct and clear.
> 

While I am not against adding bus PM ops as it can be useful elsewhere,
just wonder if this usecase is a good use of it. Does setting the state
before the pm_suspend() call suffice. I still need to think through the
possible race with that solution, but just asking you to check if that
helps.

-- 
Regards,
Sudeep