From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc.Zyngier@arm.com (Marc Zyngier) Date: Tue, 05 Apr 2011 08:30:24 +0100 Subject: [GIT PULL] omap changes for v2.6.39 merge window In-Reply-To: References: <201104031726.37420.arnd@arndb.de> <20110403160324.GA8050@n2100.arm.linux.org.uk> <201104040259.26601.arnd@arndb.de> <1301915022.15819.28.camel@e102109-lin.cambridge.arm.com> <20110404112104.GB19854@n2100.arm.linux.org.uk> <1301923457.417.34.camel@e102391-lin.cambridge.arm.com> <20110404133104.GA23266@n2100.arm.linux.org.uk> <1301925445.417.54.camel@e102391-lin.cambridge.arm.com> Message-ID: <1301988624.417.71.camel@e102391-lin.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, 2011-04-04 at 22:08 +0200, Linus Walleij wrote: > 2011/4/4 Marc Zyngier : > > On Mon, 2011-04-04 at 14:31 +0100, Russell King - ARM Linux wrote: > >> > >> If ARM are going to architect a set of timers into the hardware, let's > >> make sure that all such hardware has them so we can dig ourselves out > >> of this crappy mess that we find ourselves in today. > > > > As far as I know, A15 always has a set of generic timers. > > > > It may be that they are not available (frequency not programmed into the > > CNTFREQ register), or that someone decided to use a better alternative > > (for some particular interpretation of "better"). > > I guess this thing is inside that A15 core? > > First, what happens the day any vendors start making SoCs on this is > they turn the A15 core off whenever it is not used, loosing all state > including this timer, I believe. The main counter is located in an ALWAYS_ON power domain, and should keep going whatever happens in the system. [...] > Second, have you taken into account the effect of changing the > frequency of the A15 core, which is something every vendor also > does, as you know Colin Cross already has a patch pending > for that on the TWD localtimer which has not yet reached > the kernel. (Or is A15 fixed frequency? Forgive my ignorance...) Fixed frequency, with a minimal roll-over time of 40 years. M. -- Reality is an implementation detail.