linux-kernel - Re: [GICv3 ITS]S2IDLE framework does not invoke syscore

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Message-ID: <Z+3kwsesiXyC0hbO@perf>
Date: Thu, 3 Apr 2025 10:30:42 +0900
From: Youngmin Nam <youngmin.nam@...sung.com>
To: Sudeep Holla <sudeep.holla@....com>
Cc: Marc Zyngier <maz@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Saravana Kannan <saravanak@...gle.com>, Sudeep Holla <sudeep.holla@....com>,
	Ulf Hansson <ulf.hansson@...aro.org>, Vincent Guittot
	<vincent.guittot@...aro.org>, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, kernel-team@...roid.com,
	hajun.sung@...sung.com, d7271.choe@...sung.com, joonki.min@...sung.com,
	Youngmin Nam <youngmin.nam@...sung.com>, ne.yoo@...sung.com
Subject: Re: [GICv3 ITS]S2IDLE framework does not invoke syscore_ops in
 GICv3 ITS driver

On Wed, Apr 02, 2025 at 12:56:53PM +0100, Sudeep Holla wrote:
> (Failed to find the original email, so reply on this instead)
> 
> On Thu, Mar 27, 2025 at 12:22:19PM +0900, Youngmin Nam wrote:
> > 
> > The problem is that syscore_ops is not invoked during the S2IDLE scenario,
> > so we cannot rely on it in that context.
> > We would like to use these suspend/resume functions during S2IDLE as well.
> 
> I have one orthogonal question. The s2idle will just use the deepest
> cpuidle state registered. So if s2idle needs this save/restore of GICv3
> ITS, how does that work when all the CPUs enter that idle state.
> 
> With respect to the PSCI CPU_SUSPEND call, it doesn't change. So I am
> bit confused as how it can work fine in normal cpuidle paths but no in
> s2idle path. What am I missing ? I do psci_enter_domain_idle_state handles
> s2idle little different but nothing to change this GICv3 ITS save/restore
> requirement between cpuidle and s2idle.
> 
> -- 
> Regards,
> Sudeep
> 
Hi Sudeep,

Thanks for asking.
As a SoC vendor, we are using the Android kernel, which includes a vendor hook like the one below.

In this function,
a vendor-specific handler attached to trace_android_vh_cpuidle_psci_enter is called.

54 static __cpuidle int __psci_enter_domain_idle_state(struct cpuidle_device *dev,
55                                                     struct cpuidle_driver *drv, int idx,
56                                                     bool s2idle)
57 {
58         struct psci_cpuidle_data *data = this_cpu_ptr(&psci_cpuidle_data);
59         u32 *states = data->psci_states;
60         struct device *pd_dev = data->dev;
61         u32 state;
62         int ret;
63
64         ret = cpu_pm_enter();
65         if (ret)
66                 return -1;
67
68         /* Do runtime PM to manage a hierarchical CPU toplogy. */
69         trace_android_vh_cpuidle_psci_enter(dev, s2idle);

Within the vendor-specific handler, if the current mode is S2IDLE and the CPU logical number is 0,
the GIC ITS suspend function is executed.

Thanks.
Youngmin