Re: i.MX 7 boot freeze with 4.13-rc3

From: Stefan Agner
Date: Wed Aug 02 2017 - 14:28:24 EST

Hi Andrey,

On 2017-08-02 09:57, Andrey Smirnov wrote:
> On Tue, Aug 1, 2017 at 7:38 PM, Stefan Agner <stefan@xxxxxxxx> wrote:
>> Hi,
>> Linux 4.13-rc3 seems to freeze on a Colibri iMX7:
> Hi Stefan, sorry to hear about that.
>> ...
>> 8021q: 802.1Q VLAN Support v1.8
>> Key type dns_resolver registered
>> Registering SWP/SWPB emulation handler
>> vdd1p0d: supplied by DCDC3
> From looking briefly at the Colibir iMX7's device tree file and given
> the log line above it seems that the board has slightly different
> "vdd1p0d" power supply configuration, so it might be a good starting
> point to investigate.

That was a helpful hint, removing the vdd1p0d supply-in seems to fix the
issue. The supply seems to cause deferred probe which seems to create
the issue.

>> asoc-simple-card sound: sgtl5000 <-> 308a0000.sai mapping ok
>> <freeze>
> Not sure, but this might be a point where GPC driver will get probed
> (drivers/soc/imx/gpcv2.c) and it's possible that some of the code I
> wrote does not handle failure cases well.
>> 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:
> I don't really have a good theory WRT UART, unfortunately.
>> ...
>> io scheduler mq-deadline registered
>> io scheduler kyber registered
>> imx7-pgc imx7-pgc-domain.1: Failed to get domain's regulator
> The line above would be another clue in favor of differences in
> "vdd1p0d" configuration somehow affecting things, because
> "imx7-pgc-domain.1' is a PCIe power domain and it uses "vdd1p0d" as a
> power supply.
> ïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïïï~88ïïïïïïïïïïïïïïïï
>> 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?
> AFAIK it was tested with imx7-sdb as well as imx7d-cl-som.

Ok, since both do not use a supply-in that makes sense.

Further debugging unveiled that imx7_pgc_domain_probe executes
pm_genpd_init twice when the regulator requests deferred probing. The
easiest fix seems to reorder pm_genpd_init vs.
devm_regulator_get_optional. With that I can keep boot with supply-in
specified. I will send out a patch soon.