linux-kernel - Re: v4.17 regression: PowerMac G3 won't boot, was Re: [PATCH v5 1/3] of: cache phandle nodes to reduce cost of of_find_node_by

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Message-ID: <3d806f12-dd6f-63d7-92e0-0a79904dc4c9@gmail.com>
Date:   Sun, 9 Sep 2018 16:52:24 -0700
From:   Frank Rowand <frowand.list@...il.com>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Finn Thain <fthain@...egraphics.com.au>
Cc:     Stan Johnson <userm57@...oo.com>, Rob Herring <robh+dt@...nel.org>,
        Chintan Pandya <cpandya@...eaurora.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org,
        Frank Rowand <frowand.list@...il.com>
Subject: Re: v4.17 regression: PowerMac G3 won't boot, was Re: [PATCH v5 1/3]
 of: cache phandle nodes to reduce cost of of_find_node_by_phandle()

On 09/09/18 10:04, Benjamin Herrenschmidt wrote:
> On Fri, 2018-08-31 at 14:58 +1000, Benjamin Herrenschmidt wrote:
>>
>>> A long shot, but something to consider, is that I failed to cover the
>>> cases of dynamic devicetree updates (removing nodes that contain a
>>> phandle) in ways other than overlays.  Michael Ellerman has reported
>>> such a problem for powerpc/mobility with of_detach_node().  A patch to
>>> fix that is one of the tasks I need to complete.
>>
>> The only thing I can think of is booting via the BootX bootloader on
>> those ancient macs results in a DT with no phandles. I didn't see an
>> obvious reason why that would cause that patch to break though.
> 
> Guys, we still don't have a fix for this one on its way upstream...
> 
> My test patch just creates phandle properties for all nodes, that was
> not intended as a fix, more a way to check if the problem was related
> to the lack of phandles.
> 
> I don't actually know why the new code causes things to fail when
> phandles are absent. This needs to be looked at.
> 
> I'm travelling at the moment and generally caught up with other things,
> I haven't had a chance to dig, so just a heads up. I don't intend to
> submit my patch since it's just a band aid. We need to figure out what
> the actual problem is.
> 
> Cheers,
> Ben.

Thanks for chasing after this, and the current heads up.

I agree that we need to understand what is going on and do a real
fix.

-Frank