From mboxrd@z Thu Jan 1 00:00:00 1970 From: robherring2@gmail.com (Rob Herring) Date: Tue, 11 Dec 2012 21:01:02 -0600 Subject: Errata on multiplatform kernels In-Reply-To: <20121212005154.GY14363@n2100.arm.linux.org.uk> References: <1355203223.16750.2.camel@gitbox> <20121211180138.GB4989@atomide.com> <50C7D2AE.7050301@jonmasters.org> <20121212005154.GY14363@n2100.arm.linux.org.uk> Message-ID: <50C7F36E.3090308@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 12/11/2012 06:51 PM, Russell King - ARM Linux wrote: > On Tue, Dec 11, 2012 at 07:41:18PM -0500, Jon Masters wrote: >> On 12/11/2012 01:01 PM, Tony Lindgren wrote: >>> * Olof Johansson [121210 21:38]: >>>> Hi, >>>> >>>> On Mon, Dec 10, 2012 at 9:20 PM, Tony Prisk wrote: >>>>> How are errata handled on multiplatform kernels? >>>>> >>>>> There don't appear to be any errata selected by default in any of the >>>>> current multiplatform options, but presumably it will happen eventually. >>>>> >>>>> Does that mean the errata will be applied to all machines that boot with >>>>> the errata selected, even if not required? >>>> >>>> Yes. To date I believe most errata we have are just performance hits >>>> on platforms that don't need it. >>>> >>>> Other architectures have in some cases added runtime patching (out) of >>>> workarounds that aren't needed on the current platform for the ones >>>> that have significant performance impact. I'm guessing we'll end up >>>> with something similar eventually but until then we'll try to just go >>>> with the superset of needed errata. >>> >>> We can't enable any of the errata if there's a chance that it will behave >>> in a different way for secure mode devices compared to non-secure devices. >>> >>> The discussion is in the thread "[PATCH] ARM: Fix errata 751472 handling >>> on Cortex-A9 r1p*". >>> >>> The conclusion was that we cannot enable any errata for multiplatform, >>> and must assume the errata is handled by the bootloader. Multiplatform >>> image is already broken for at least omap4 as 751472 is selected. >> >> On some platforms with a PL310 we have errata 588369 and 727915 >> (especially enabled on OMAP4 targets) which will cause an external abort >> when enabled and then booted on highbank systems. This has taken the >> last couple of days on and off to track down. So I guess we need to >> basically disable these in our (Fedora) multiplatform kernel and then >> assume that e.g. PandaBoard will implement some U-Boot fix if it needs >> to have one? Not sure exactly what that fix is going to look like :) > > Neither 588369 nor 727915 are something a boot loader can do - they have > to be done in the kernel. If they're causing highbank systems to fail > that needs to be debugged. > > My guess is that highbank is another non-secure system, and the L2x0 > code is trying to use pl310_set_debug() which will fail on non-secure > systems as the 'set_debug' hook is not being overriden. > > If there was a way to tell that we're running on a non-secure system, > we could automatically point set_debug() to a nop function, but it > would be far more preferable for highbank to provide the hook. (That > could be itself a no-op if it doesn't require the work-around.) Actually, we should check the pl310 revision and set .set_debug to NULL on r3p1 and later. This will fix highbank and any other platform that doesn't need the work-around. I'd assume platforms that are non-secure and need this work-around will override .set_debug. I'll work on a patch. Rob > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >