From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Stephen Warren <swarren@wwwdotorg.org>,
Thierry Reding <thierry.reding@gmail.com>,
Alexandre Courbot <gnurou@gmail.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Kyungmin Park <kyungmin.park@samsung.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Kukjin Kim <kgene.kim@samsung.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ARM: tegra: cpuidle: implement cpuidle_state.enter_freeze()
Date: Sat, 16 May 2015 00:30:41 +0100 [thread overview]
Message-ID: <20150515233041.GN2067@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAAObsKBLHqf1+KUE89Orr7ZwzY3-WEW1CHokSOxSD9pEOmTkhg@mail.gmail.com>
On Fri, May 15, 2015 at 11:03:35AM +0200, Tomeu Vizoso wrote:
> I have been looking and asking around, and seems like we should
> actually leave FIQs enabled when the tick is frozen and only disable
> them within enter_freeze.
>
> My understanding is that FIQ handlers are extremely limited in what
> they can do, with the main use being NMI-like functionality. There are
> a handful of other FIQ handlers in mainline, but they don't call into
> any other kernel code and limit themselves to doing some basic I/O.
>
> The only reason why they should be disabled in enter_freeze is that
> the context of the CPU that is going to a lower power state could
> become corrupted if a FIQ gets fired during a save or restore
> operation.
Right, that makes total sense.
(And yes, FIQ handlers are very limited in what they're allowed to do,
since they can't take any locks without the potential for deadlock.)
--
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.
prev parent reply other threads:[~2015-05-15 23:31 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-08 10:54 Tomeu Vizoso
2015-04-08 11:55 ` Lorenzo Pieralisi
2015-04-09 9:18 ` Tomeu Vizoso
2015-04-09 21:19 ` Rafael J. Wysocki
2015-04-10 10:08 ` Lorenzo Pieralisi
2015-04-16 14:37 ` Tomeu Vizoso
2015-04-17 14:08 ` Lorenzo Pieralisi
2015-04-17 15:02 ` Tomeu Vizoso
2015-04-28 15:07 ` Tomeu Vizoso
2015-05-15 9:03 ` Tomeu Vizoso
2015-05-15 23:30 ` Russell King - ARM Linux [this message]
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