linux-kernel - Re: [RFC PATCH v3 5/5] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

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Date: Fri, 22 Mar 2024 16:02:12 +0000
From: Marc Zyngier <maz@...nel.org>
To: David Woodhouse <dwmw2@...radead.org>
Cc: linux-arm-kernel@...ts.infradead.org,
	kvm@...r.kernel.org,
	Paolo Bonzini <pbonzini@...hat.com>,
	Jonathan Corbet <corbet@....net>,
	Oliver Upton <oliver.upton@...ux.dev>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>,
	David Woodhouse <dwmw@...zon.co.uk>,
	Mostafa Saleh <smostafa@...gle.com>,
	Jean-Philippe Brucker <jean-philippe@...aro.org>,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev,
	linux-pm@...r.kernel.org
Subject: Re: [RFC PATCH v3 5/5] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate

On Tue, 19 Mar 2024 12:59:06 +0000,
David Woodhouse <dwmw2@...radead.org> wrote:

[...]

> +static void __init psci_init_system_off2(void)
> +{
> +	int ret;
> +
> +	ret = psci_features(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2));
> +
> +	if (ret != PSCI_RET_NOT_SUPPORTED)
> +		psci_system_off2_supported = true;

It'd be worth considering the (slightly broken) case where SYSTEM_OFF2
is supported, but HIBERNATE_OFF is not set in the response, as the
spec doesn't say that this bit is mandatory (it seems legal to
implement SYSTEM_OFF2 without any hibernate type, making it similar to
SYSTEM_OFF).

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.