On 30/03/15 16:39, Sudeep Holla wrote:

On 30/03/15 16:05, Russell King - ARM Linux wrote:

quoted

On Mon, Mar 30, 2015 at 03:48:08PM +0100, Sudeep Holla wrote:

quoted

Though <2 2 1> works fine most of the time, I did try testing continuous
reboot overnight and it failed. I kept increasing the latencies and
found out that even max latency of <8 8 8> could not survive continuous
overnight reboot test and it fails with exact same issue.

So I am not sure if we can consider it as a fix. However if we are OK to
have *mostly reliable*, then we can push that change.

Okay, the issue I have is this.

Versatile Express used to boot reliably in the nightly build tests prior
to DT.  In that mode, we never configured the latency values.

I have never run in legacy mode as I am relatively new to vexpress
platform and started using with DT from first. Just to understand better
I had a look at the commit commit 81cc3f868d30("ARM: vexpress: Remove
non-DT code") and I see the below function in
arch/arm/mach-vexpress/ct-ca9x4.c So I assume we were programming one
cycle for all the latencies just like DT.

I was able to boot v3.18 without DT and I compared the L2C settings with
and w/o DT, they are identical. Also v3.18 with and w/o DT survived
overnight reboot testing.

quoted

Then the legacy code was removed, and I had to switch over to DT booting,
and shortly after I noticed that the platform was now randomly failing
its nightly boot tests.

Maybe we should revert the commit removing the superior legacy code,
because that seems to be the only thing that was reliable?  Maybe it was
premature to remove it until DT had proven itself?

Not sure on that as v3.18 with DT seems to be working fine and passed
overnight reboot testing.

quoted

On the other hand, if the legacy code hadn't been removed, I probably
would never have tested it - but then, from what I hear, this was a
*known* issue prior to the removal of the legacy code.  Given that the
legacy code worked totally fine, it's utterly idiotic to me to have
removed the working legacy code when DT is soo unstable.

Whatever way I look at this, this problem _is_ a _regression_, and we
can't sit around and hope it magically vanishes by some means.

I agree, last time I tested it was fine with v3.18. However I have not
run the continuous overnight reboot test on that. I will first started
looking at that, just to see if it's issue related to DT vs legacy boot.

Since v3.18 is both boot modes and the problem is reproducible on
v3.19-rc1. I am trying to bisect but not sure if that's feasible for
such a problem. I also found out by accident that even on mainline with
more configs enabled, it's hard to hit the issue.

Regards,
Sudeep