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

[tony@atomide.com (Tony Lindgren)]

* Felipe Balbi <balbi@ti.com> [150223 18:28]:
> Hi,
> 
> On Mon, Feb 23, 2015 at 05:59:04PM -0800, Tony Lindgren wrote:
> > * Tony Lindgren <tony@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..

Regards,

Tony