Re: [PATCH] clk: composite: Also consider .determine_rate for rate + mux composites

[Robin Murphy <robin.murphy@arm.com>]

On 2021-11-01 21:59, Robin Murphy wrote:
> On 2021-11-01 20:58, Martin Blumenstingl wrote:
>> Hi Guillaume,
>>
>> On Mon, Nov 1, 2021 at 9:19 PM Guillaume Tucker
>> <guillaume.tucker@collabora.com> wrote:
>>>
>>> Hi Martin,
>>>
>>> Please see the bisection report below about a boot failure on
>>> rk3328-rock64.
>>>
>>> Reports aren't automatically sent to the public while we're
>>> trialing new bisection features on kernelci.org but this one
>>> looks valid.
>>>
>>> Some more details can be found here:
>>>
>>>    https://linux.kernelci.org/test/case/id/617f11f5c157b666fb3358e6/
>>>
>>> Here's what appears to be the cause of the problem:
>>>
>>> [    0.033465] CPU: CPUs started in inconsistent modes
>>> [    0.033557] Unexpected kernel BRK exception at EL1
>>> [    0.034432] Internal error: BRK handler: f2000800 [#1] PREEMPT SMP
> 
> What's weird is that that's really just the same WARN that's also 
> present in 'successful' logs, except for some reason it's behaving as if 
> the break handler hasn't been registered, despite that having happened 
> long before we got to smp_init(). At this point we're also still some 
> way off getting as far as initcalls, so I'm not sure that the clock 
> driver would be in the picture at all yet.
> 
> Is the bisection repeatable, or is this just random flakiness misleading 
> things? I'd also note that you need pretty horrifically broken firmware 
> to hit that warning in the first place, which might cast a bit of doubt 
> over the trustworthiness of that board altogether.

Ah, on closer inspection it might be entirely repeatable for a given 
kernel build, but with the behaviour being very sensitive to code/data 
segment layout changes...

...
23:44:24.457917  Filename '1007060/tftp-deploy-dvdnydcw/kernel/Image'.
23:44:24.460178  Load address: 0x2000000
...
23:44:27.180962  Bytes transferred = 33681920 (201f200 hex)
...
23:44:27.288135  Filename 
'1007060/tftp-deploy-dvdnydcw/ramdisk/ramdisk.cpio.gz.uboot'.
23:44:27.288465  Load address: 0x4000000
...

Yeah, that'll be a problem ;)

Cheers,
Robin.

>>> There doesn't appear to be any other platform in KernelCI showing
>>> the same issue.
>> That's a strange error for the changes from my patch.
>> At first glance I don't see any relation to clk-composite code:
>> - the call trace doesn't have any references to CCF or rockchip clock 
>> drivers
>> - clk-rk3328.c uses drivers/clk/rockchip/clk-cpu.c to register the CPU
>> clock which does not use clk-composite
>>
>> Chen-Yu has tested this patch (plus [0]) on RK3399 and didn't observe
>> any problems.
>> So maybe this is a RK3328 specific issue?
>> Anyways, I am interested in fixing this issue because reverting is
>> becoming more and more complex (since I think we're at eight commits
>> which would need to be reverted in total).
>>
>>> Please let us know if you need help debugging the issue or if you
>>> have a fix to try.
>> Could you please try [0] which is the second patch in the series which
>> finally made it upstream.
>> This second patch is not in 5.15 because I believed that it's only
>> something to make the code in clk-composite.c more future-proof. It's
>> not a condition that I am aware of.
>>
>> I don't have any Rockchip boards myself.
>> So I am thankful for any help I can get.
>>
>>
>> Best regards,
>> Martin
>>
>>
>> [0] 
>> https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git/commit/?h=clk-next&id=6594988fd625ff0d9a8f90f1788e16185358a3e6 
>>
>>
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>>
> 
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