From: Nicolas Pitre <nicolas.pitre@linaro.org>
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Mark Rutland <Mark.Rutland@arm.com>,
Catalin Marinas <Catalin.Marinas@arm.com>,
Tomasz Figa <t.figa@samsung.com>,
Lina Iyer <lina.iyer@linaro.org>,
Chander Kashyap <k.chander@samsung.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"grant.likely@linaro.org" <grant.likely@linaro.org>,
Charles Garcia-Tobin <Charles.Garcia-Tobin@arm.com>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Kevin Hilman <khilman@linaro.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
Sebastian Capella <sebcape@gmail.com>,
Mark Brown <broonie@kernel.org>, Antti Miettinen <ananaza@iki.fi>,
Paul Walmsley <paul@pwsan.com>,
Geoff Levand <geoff@infradead.org>,
Peter De Schrijver <pdeschrijver@nvidia.com>,
Stephen Boyd <sboyd@codeaurora.org>,
Amit
Subject: Re: [PATCH v7 3/8] drivers: cpuidle: implement DT based idle states infrastructure
Date: Wed, 13 Aug 2014 13:29:49 -0400 (EDT) [thread overview]
Message-ID: <alpine.LFD.2.11.1408131319210.1133@knanqh.ubzr> (raw)
In-Reply-To: <20140813170440.GA30822@e102568-lin.cambridge.arm.com>
On Wed, 13 Aug 2014, Lorenzo Pieralisi wrote:
> On Wed, Aug 13, 2014 at 05:31:11PM +0100, Nicolas Pitre wrote:
> > On Wed, 13 Aug 2014, Lorenzo Pieralisi wrote:
> >
> > > On most common ARM systems, the low-power states a CPU can be put into are
> > > not discoverable in HW and require device tree bindings to describe
> > > power down suspend operations and idle states parameters.
> > >
> > > In order to enable DT based idle states and configure idle drivers, this
> > > patch implements the bulk infrastructure required to parse the device tree
> > > idle states bindings and initialize the corresponding CPUidle driver states
> > > data.
> > >
> > > The parsing API accepts a start index that defines the first idle state
> > > that should be initialized by the parsing code in order to give new and
> > > legacy driver flexibility over which states should be parsed using the
> > > new DT mechanism.
> > >
> > > The idle states list is obtained from the first cpu in the driver
> > > cpumask, which implicitly means the parsing code expects idle states
> > > (and related list of phandles) to be the same for all CPUs in the
> > > CPUidle driver mask. The kernel does not check this assumption, it must
> > > be enforced by the bootloader to ensure correct system behaviour.
> >
> > Can we make the kernel a little less reliant on bootloader to ensure
> > correct system behaviour please? If assumptions are assumed by the
> > kernel, it should at least print a warning and simply ignore the
> > information when such assumption are not respected.
>
> I think the check adds complexity (it means stashing the idle states
> phandles for the first cpu, loop through the cpus in the mask and compare
> the phandles to the ones stashed for the first cpu for all cpus in the
> driver mask) for not much.
>
> I was told that it is not up to the kernel to validate the DT, but if
> you want I can implement the check even though I really think it is
> overkill.
DT validation is not the same as resiliance against messed-up DT
content. If the kernel is going to boot regardless then this is fine.
If the kernel is going to crash, or work suboptimally without returning
a clue because some implicit assumptions are not respected then this is
bad.
And people _will_ mess up their DT from time to time.
So if you tell me a messed-up DT won't bear much consequences then I'm
fine with that.
Nicolas
WARNING: multiple messages have this Message-ID (diff)
From: nicolas.pitre@linaro.org (Nicolas Pitre)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v7 3/8] drivers: cpuidle: implement DT based idle states infrastructure
Date: Wed, 13 Aug 2014 13:29:49 -0400 (EDT) [thread overview]
Message-ID: <alpine.LFD.2.11.1408131319210.1133@knanqh.ubzr> (raw)
In-Reply-To: <20140813170440.GA30822@e102568-lin.cambridge.arm.com>
On Wed, 13 Aug 2014, Lorenzo Pieralisi wrote:
> On Wed, Aug 13, 2014 at 05:31:11PM +0100, Nicolas Pitre wrote:
> > On Wed, 13 Aug 2014, Lorenzo Pieralisi wrote:
> >
> > > On most common ARM systems, the low-power states a CPU can be put into are
> > > not discoverable in HW and require device tree bindings to describe
> > > power down suspend operations and idle states parameters.
> > >
> > > In order to enable DT based idle states and configure idle drivers, this
> > > patch implements the bulk infrastructure required to parse the device tree
> > > idle states bindings and initialize the corresponding CPUidle driver states
> > > data.
> > >
> > > The parsing API accepts a start index that defines the first idle state
> > > that should be initialized by the parsing code in order to give new and
> > > legacy driver flexibility over which states should be parsed using the
> > > new DT mechanism.
> > >
> > > The idle states list is obtained from the first cpu in the driver
> > > cpumask, which implicitly means the parsing code expects idle states
> > > (and related list of phandles) to be the same for all CPUs in the
> > > CPUidle driver mask. The kernel does not check this assumption, it must
> > > be enforced by the bootloader to ensure correct system behaviour.
> >
> > Can we make the kernel a little less reliant on bootloader to ensure
> > correct system behaviour please? If assumptions are assumed by the
> > kernel, it should at least print a warning and simply ignore the
> > information when such assumption are not respected.
>
> I think the check adds complexity (it means stashing the idle states
> phandles for the first cpu, loop through the cpus in the mask and compare
> the phandles to the ones stashed for the first cpu for all cpus in the
> driver mask) for not much.
>
> I was told that it is not up to the kernel to validate the DT, but if
> you want I can implement the check even though I really think it is
> overkill.
DT validation is not the same as resiliance against messed-up DT
content. If the kernel is going to boot regardless then this is fine.
If the kernel is going to crash, or work suboptimally without returning
a clue because some implicit assumptions are not respected then this is
bad.
And people _will_ mess up their DT from time to time.
So if you tell me a messed-up DT won't bear much consequences then I'm
fine with that.
Nicolas
next prev parent reply other threads:[~2014-08-13 17:29 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-13 15:51 [PATCH v7 0/8] ARM generic idle states Lorenzo Pieralisi
2014-08-13 15:51 ` Lorenzo Pieralisi
2014-08-13 15:52 ` [PATCH v7 1/8] arm64: kernel: refactor the CPU suspend API for retention states Lorenzo Pieralisi
2014-08-13 15:52 ` Lorenzo Pieralisi
2014-08-18 7:47 ` Hanjun Guo
2014-08-18 7:47 ` Hanjun Guo
2014-08-18 14:20 ` Catalin Marinas
2014-08-18 14:20 ` Catalin Marinas
2014-08-13 15:52 ` [PATCH v7 2/8] Documentation: arm: define DT idle states bindings Lorenzo Pieralisi
2014-08-13 15:52 ` Lorenzo Pieralisi
[not found] ` <1407945127-27554-3-git-send-email-lorenzo.pieralisi-5wv7dgnIgG8@public.gmane.org>
2014-08-13 19:25 ` Lina Iyer
2014-08-13 19:25 ` Lina Iyer
2014-08-13 22:11 ` Lorenzo Pieralisi
2014-08-13 22:11 ` Lorenzo Pieralisi
2014-08-15 17:20 ` Lina Iyer
2014-08-15 17:20 ` Lina Iyer
2014-08-15 17:51 ` Lorenzo Pieralisi
2014-08-15 17:51 ` Lorenzo Pieralisi
2014-08-18 14:20 ` Catalin Marinas
2014-08-18 14:20 ` Catalin Marinas
2014-08-13 15:52 ` [PATCH v7 3/8] drivers: cpuidle: implement DT based idle states infrastructure Lorenzo Pieralisi
2014-08-13 15:52 ` Lorenzo Pieralisi
2014-08-13 16:31 ` Nicolas Pitre
2014-08-13 16:31 ` Nicolas Pitre
2014-08-13 17:04 ` Lorenzo Pieralisi
2014-08-13 17:04 ` Lorenzo Pieralisi
2014-08-13 17:29 ` Nicolas Pitre [this message]
2014-08-13 17:29 ` Nicolas Pitre
2014-08-14 11:29 ` Lorenzo Pieralisi
2014-08-14 11:29 ` Lorenzo Pieralisi
2014-08-14 15:47 ` Nicolas Pitre
2014-08-14 15:47 ` Nicolas Pitre
2014-08-14 16:02 ` Lorenzo Pieralisi
2014-08-14 16:02 ` Lorenzo Pieralisi
2014-08-18 14:21 ` Catalin Marinas
2014-08-18 14:21 ` Catalin Marinas
2014-08-13 15:52 ` [PATCH v7 4/8] arm64: kernel: introduce cpu_init_idle CPU operation Lorenzo Pieralisi
2014-08-13 15:52 ` Lorenzo Pieralisi
2014-08-18 14:21 ` Catalin Marinas
2014-08-18 14:21 ` Catalin Marinas
[not found] ` <1407945127-27554-1-git-send-email-lorenzo.pieralisi-5wv7dgnIgG8@public.gmane.org>
2014-08-13 15:52 ` [PATCH v7 5/8] arm64: add PSCI CPU_SUSPEND based cpu_suspend support Lorenzo Pieralisi
2014-08-13 15:52 ` Lorenzo Pieralisi
2014-08-18 14:21 ` Catalin Marinas
2014-08-18 14:21 ` Catalin Marinas
2014-08-13 15:52 ` [PATCH v7 6/8] drivers: cpuidle: CPU idle ARM64 driver Lorenzo Pieralisi
2014-08-13 15:52 ` Lorenzo Pieralisi
2014-08-18 14:21 ` Catalin Marinas
2014-08-18 14:21 ` Catalin Marinas
2014-08-18 22:30 ` Lorenzo Pieralisi
2014-08-18 22:30 ` Lorenzo Pieralisi
2014-08-18 14:21 ` Catalin Marinas
2014-08-18 14:21 ` Catalin Marinas
2014-08-18 22:25 ` Lorenzo Pieralisi
2014-08-18 22:25 ` Lorenzo Pieralisi
2014-08-13 15:52 ` [PATCH v7 7/8] drivers: cpuidle: initialize big.LITTLE driver through DT Lorenzo Pieralisi
2014-08-13 15:52 ` Lorenzo Pieralisi
2014-08-18 14:21 ` Catalin Marinas
2014-08-18 14:21 ` Catalin Marinas
2014-08-13 15:52 ` [PATCH v7 8/8] drivers: cpuidle: initialize Exynos " Lorenzo Pieralisi
2014-08-13 15:52 ` Lorenzo Pieralisi
2014-08-15 21:12 ` Lina Iyer
2014-08-15 21:12 ` Lina Iyer
2014-08-15 21:40 ` Lorenzo Pieralisi
2014-08-15 21:40 ` Lorenzo Pieralisi
2014-08-15 21:45 ` Lina Iyer
2014-08-15 21:45 ` Lina Iyer
2014-08-15 21:52 ` Lorenzo Pieralisi
2014-08-15 21:52 ` Lorenzo Pieralisi
2014-08-18 14:22 ` Catalin Marinas
2014-08-18 14:22 ` Catalin Marinas
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