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

From: Marc Zyngier <maz@kernel.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
	Paolo Bonzini <pbonzini@redhat.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Oliver Upton <oliver.upton@linux.dev>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Lorenzo Pieralisi <lpieralisi@kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Mostafa Saleh <smostafa@google.com>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	kvmarm@lists.linux.dev, linux-pm@vger.kernel.org
Subject: Re: [RFC PATCH v3 5/5] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate
Date: Fri, 22 Mar 2024 16:02:12 +0000	[thread overview]
Message-ID: <86jzluz24b.wl-maz@kernel.org> (raw)
In-Reply-To: <20240319130957.1050637-6-dwmw2@infradead.org>

On Tue, 19 Mar 2024 12:59:06 +0000,
David Woodhouse <dwmw2@infradead.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.