i.MX 7 boot freeze with 4.13-rc3

From: Stefan Agner
Date: Tue Aug 01 2017 - 22:40:29 EST


Linux 4.13-rc3 seems to freeze on a Colibri iMX7:

8021q: 802.1Q VLAN Support v1.8
Key type dns_resolver registered
Registering SWP/SWPB emulation handler
vdd1p0d: supplied by DCDC3
asoc-simple-card sound: sgtl5000 <-> 308a0000.sai mapping ok

I started a bisect run and I had a hard time to get properly through
imx-dt-4.13. On the imx-dt branch the i.MX 7 GPC changes seem to cause
the UART to only output garbage:

io scheduler mq-deadline registered
io scheduler kyber registered
imx7-pgc imx7-pgc-domain.1: Failed to get domain's regulator

It turned out at the merge point 2cb6115deba0 (Merge tag 'imx-dt-4.13'
of...) the behavior changed to the freeze seen in 4.13-rc3.

Reverting 0f90b43ac71b (ARM: dts: imx7s: Add node for GPC) helped in
both cases, and when using v4.13-rc3 (I also had to revert a816d5750edf
and 34adfaa3d404 which depend on this GPC change).

I assume that the merge adds driver changes which changes the behavior
of the GPC driver, hence freeze vs. garbage?

At the moment it is unclear to me why the GPC change leads to freezes on
our platform. On which platform have this changes been tested? Any other
i.MX 7 platforms seeing freezes?