From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Wed, 12 Dec 2012 00:51:54 +0000 Subject: Errata on multiplatform kernels In-Reply-To: <50C7D2AE.7050301@jonmasters.org> References: <1355203223.16750.2.camel@gitbox> <20121211180138.GB4989@atomide.com> <50C7D2AE.7050301@jonmasters.org> Message-ID: <20121212005154.GY14363@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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.)