New l3-noc error with CPUFREQ_DT built-in with v4.0-rc1

[Tony Lindgren]

* Tony Lindgren <tony at atomide.com> [150223 18:43]:
> * Felipe Balbi <balbi at ti.com> [150223 18:28]:
> > Hi,
> > 
> > On Mon, Feb 23, 2015 at 05:59:04PM -0800, Tony Lindgren wrote:
> > > * Tony Lindgren <tony at atomide.com> [150223 16:09]:
> > > > Hi Nishanth,
> > > > 
> > > > Olof told me about a new L3 error happening on omap5-uevm with
> > > > v4.0-rc1:
> > > > 
> > > > WARNING: CPU: 0 PID: 0 at drivers/bus/omap_l3_noc.c:147 l3_interrupt_handler+0x214/0x340()
> > > > 4000000.ocp:L3 Custom Error: MASTER MPU TARGET L4PER2 (Idle): Data Access in Supervisor mode during Functional access
> > > > ...
> > > > 
> > > > I tried bisecting this with no luck, but narrowed it down to
> > > > having CONFIG_CPUFREQ_DT=y causing it, while =m wont' trigger
> > > > it. This got changed by commit 40d1746d2eee ("ARM:
> > > > omap2plus_defconfig: use CONFIG_CPUFREQ_DT").
> > > > 
> > > > Any ideas?
> > > 
> > > Hmm so setting CONFIG_CPUFREQ_DT=m in arch/arm/configs/omap2plus_defconfig
> > > produces the same output with make omap2plus_defconfig as with =y.. So
> > > CPUFREQ_DT can't be the real cause of the problem.
> > > 
> > > It's now looking like the l3-noc warning does not get triggered on
> > > every boot.
> > > 
> > > It also seems the zImage triggering the error does not trigger the
> > > error on every boot. To trigger the error, it seems the device needs to
> > > be powered down for at least 10 or so seconds between the boots.
> > > So far no luck reproducing the error on v3.19.
> > > 
> > > The easy way to reproduce is to power down omap5 for at least 10 seconds,
> > > make omap2lus_defconfig on v4.0-rc1 and boot it.
> > > 
> > > And so far it looks like next-20150204 works and next-20150209
> > > failed at once so far. But of course I would not trust anything
> > > at this point :)
> > 
> > got a log of the failure ? Is it pointing to a device or one of the L4s?
> 
> Well mostly the MASTER MPU TARGET L4PER2, the following stack dump is
> really the stack dump of the l3_interrupt_handler.
>  
> > Might be worth to boot with just the bare minimum (UART & timers) and
> > disable everything else. You might need to build busybox and append that
> > to the kernel so you don't need to rely on MMC/USB/etc for rootfs.
> > 
> > After that, you could start enabling modules one by one (as modules, not
> > built-in) and loading them one by one to see which one causes the
> > failure. Big PITA, I know, but I can't think of any other way to go
> > about this.
> 
> It seems the best way to deal with this is to make the l3_handle_target
> actually show the address where the error happened to limit it down
> to a single device..

Looks like the address is 0 for "Custom Error". Anyways, reverting
a fix for similar issue found on omap3 so far seems to help, that's
3d009c8c61f9 ("gpio: omap: Fix bad device access with setup_irq()").

That got merged very late for v3.19, so it certainly explains why
it was not noticed until now.

Regards,

Tony