Re: next/master bisection: baseline.dmesg.emerg on meson-gxbb-p200

[Marc Zyngier]

On 2020-11-19 10:26, Neil Armstrong wrote:
> On 19/11/2020 11:20, Marc Zyngier wrote:
> > On 2020-11-19 08:50, Guillaume Tucker wrote:
> > > Please see the automated bisection report below about some kernel
> > > errors on meson-gxbb-p200.
> > >
> > > Reports aren't automatically sent to the public while we're
> > > trialing new bisection features on kernelci.org, however this one
> > > looks valid.
> > >
> > > The bisection started with next-20201118 but the errors are still
> > > present in next-20201119.  Details for this regression:
> > >
> > >   https://kernelci.org/test/case/id/5fb6196bfd0127fd68d8d902/
> > >
> > > The first error is:
> > >
> > >   [   14.757489] Internal error: synchronous external abort: 96000210
> > > [#1] PREEMPT SMP
> >
> > Looks like yet another clock ordering setup. I guess different Amlogic
> > platforms have slightly different ordering requirements.
> >
> > Neil, do you have any idea of which platform requires which ordering?
> > The variability in DT and platforms is pretty difficult to follow (and
> > I don't think I have such board around).
>
> The requirements should be the same, here the init was done before 
> calling
> dw_hdmi_probe to be sure the clocks and internals resets were 
> deasserted.
> But since you boot from u-boot already enabling these, it's already 
> active.

The crashing platform also boots with u-boot. What is the difference?
No HDMI support?

> The solution would be to revert and do some check in 
> meson_dw_hdmi_init() to
> check if already enabled and do nothing.

It looks more subtle than that, as it also depends on which DT is 
provided
(an early meson_dw_hdmi_init() works with the kernel DT, and breaks with 
the
u-boot DT). So whatever difference is between the two DTs causes havoc.
u-boot obviously only uses its own DT, so we are looking at a kernel bug 
here.

Not having this patch also breaks module reinsertion (HDMI clocks are 
disabled
on unbind), so *something* has to be done late.

So here are my questions:
- What breaks in my config when I boot using u-boot's DT?
- How to detect early that the registers are clocked or not?

Thanks,

        M.
--
Jazz is not dead. It just smells funny...