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

[Felipe Balbi]

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?

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.

-- 
balbi
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