Re: [PATCH 5/9] ARM: dts: exynos: move exynos-bus nodes out of soc in Exynos4412

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 24/03/2023 18:07, Marek Szyprowski wrote:
> On 06.02.2023 17:12, Krzysztof Kozlowski wrote:
>> On 03/02/2023 23:50, Marek Szyprowski wrote:
>>> On 03.02.2023 22:12, Krzysztof Kozlowski wrote:
>>>> On 03/02/2023 21:34, Krzysztof Kozlowski wrote:
>>>>> On 03/02/2023 12:51, Marek Szyprowski wrote:
>>>>>> On 03.02.2023 12:46, Krzysztof Kozlowski wrote:
>>>>>>> On 03/02/2023 12:45, Marek Szyprowski wrote:
>>>>>>>> On 29.01.2023 11:42, Krzysztof Kozlowski wrote:
>>>>>>>>> On 25/01/2023 10:45, Krzysztof Kozlowski wrote:
>>>>>>>>>> The soc node is supposed to have only device nodes with MMIO addresses,
>>>>>>>>>> as reported by dtc W=1:
>>>>>>>>>>
>>>>>>>>>>       exynos4412.dtsi:407.20-413.5:
>>>>>>>>>>         Warning (simple_bus_reg): /soc/bus-acp: missing or empty reg/ranges property
>>>>>>>>>>
>>>>>>>>>> and dtbs_check:
>>>>>>>>>>
>>>>>>>>>>       exynos4412-i9300.dtb: soc: bus-acp:
>>>>>>>>>>         {'compatible': ['samsung,exynos-bus'], 'clocks': [[7, 456]], 'clock-names': ['bus'], 'operating-points-v2': [[132]], 'status': ['okay'], 'devfreq': [[117]]} should not be valid under {'type': 'object'}
>>>>>>>>>>
>>>>>>>>>> Move the bus nodes and their OPP tables out of SoC to fix this.
>>>>>>>>>> Re-order them alphabetically while moving and put some of the OPP tables
>>>>>>>>>> in device nodes (if they are not shared).
>>>>>>>>>>
>>>>>>>>> Applied.
>>>>>>>> I don't have a good news. It looks that this change is responsible for
>>>>>>>> breaking boards that were rock-stable so far, like Odroid U3. I didn't
>>>>>>>> manage to analyze what exactly causes the issue, but it looks that the
>>>>>>>> exynos-bus devfreq driver somehow depends on the order of the nodes:
>>>>>>>>
>>>>>>>> (before)
>>>>>>>>
>>>>>>>> # dmesg | grep exynos-bus
>>>>>>>> [    6.415266] exynos-bus: new bus device registered: soc:bus-dmc
>>>>>>>> (100000 KHz ~ 400000 KHz)
>>>>>>>> [    6.422717] exynos-bus: new bus device registered: soc:bus-acp
>>>>>>>> (100000 KHz ~ 267000 KHz)
>>>>>>>> [    6.454323] exynos-bus: new bus device registered: soc:bus-c2c
>>>>>>>> (100000 KHz ~ 400000 KHz)
>>>>>>>> [    6.489944] exynos-bus: new bus device registered: soc:bus-leftbus
>>>>>>>> (100000 KHz ~ 200000 KHz)
>>>>>>>> [    6.493990] exynos-bus: new bus device registered: soc:bus-rightbus
>>>>>>>> (100000 KHz ~ 200000 KHz)
>>>>>>>> [    6.494612] exynos-bus: new bus device registered: soc:bus-display
>>>>>>>> (160000 KHz ~ 200000 KHz)
>>>>>>>> [    6.494932] exynos-bus: new bus device registered: soc:bus-fsys
>>>>>>>> (100000 KHz ~ 134000 KHz)
>>>>>>>> [    6.495246] exynos-bus: new bus device registered: soc:bus-peri (
>>>>>>>> 50000 KHz ~ 100000 KHz)
>>>>>>>> [    6.495577] exynos-bus: new bus device registered: soc:bus-mfc
>>>>>>>> (100000 KHz ~ 200000 KHz)
>>>>>>>>
>>>>>>>> (after)
>>>>>>>>
>>>>>>>> # dmesg | grep exynos-bus
>>>>>>>>
>>>>>>>> [    6.082032] exynos-bus: new bus device registered: bus-dmc (100000
>>>>>>>> KHz ~ 400000 KHz)
>>>>>>>> [    6.122726] exynos-bus: new bus device registered: bus-leftbus
>>>>>>>> (100000 KHz ~ 200000 KHz)
>>>>>>>> [    6.146705] exynos-bus: new bus device registered: bus-mfc (100000
>>>>>>>> KHz ~ 200000 KHz)
>>>>>>>> [    6.181632] exynos-bus: new bus device registered: bus-peri ( 50000
>>>>>>>> KHz ~ 100000 KHz)
>>>>>>>> [    6.204770] exynos-bus: new bus device registered: bus-rightbus
>>>>>>>> (100000 KHz ~ 200000 KHz)
>>>>>>>> [    6.211087] exynos-bus: new bus device registered: bus-acp (100000
>>>>>>>> KHz ~ 267000 KHz)
>>>>>>>> [    6.216936] exynos-bus: new bus device registered: bus-c2c (100000
>>>>>>>> KHz ~ 400000 KHz)
>>>>>>>> [    6.225748] exynos-bus: new bus device registered: bus-display
>>>>>>>> (160000 KHz ~ 200000 KHz)
>>>>>>>> [    6.242978] exynos-bus: new bus device registered: bus-fsys (100000
>>>>>>>> KHz ~ 134000 KHz)
>>>>>>>>
>>>>>>>> This is definitely a driver bug, but so far it worked fine, so this is a
>>>>>>>> regression that need to be addressed somehow...
>>>>>>> Thanks for checking, but what is exactly the bug? The devices registered
>>>>>>> - just with different name.
>>>>>> The bug is that the board fails to boot from time to time, freezing
>>>>>> after registering PPMU counters...
>>>>> My U3 with and without this patch, reports several warnings:
>>>>> iommu_group_do_set_platform_dma()
>>>>> exynos_iommu_domain_free()
>>>>> clk_core_enable()
>>>>>
>>>>> and finally:
>>>>> rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
>>>>>
>>>>> and keeps stalling.
>>>>>
>>>>> At least on next-20230203. Except all these (which anyway make board
>>>>> unbootable) look fine around PMU and exynos-bus.
>>>> I also booted few times my next/dt branch (with this patch) and no
>>>> problems. How reproducible is the issue you experience?
>>> IOMMU needs a fixup, that has been merged today:
>>>
>>> https://lore.kernel.org/all/20230123093102.12392-1-m.szyprowski@samsung.com/
>>>
>>> I was initially convinced that this freeze is somehow related to this
>>> IOMMU fixup, but it turned out that the devfreq is a source of the problems.
>>>
>>> The freeze happens here about 1 of 10 boots, usually with kernel
>>> compiled from multi_v7_defconfig, while loading the PPMU modules. It
>>> happens on your next/dt branch too.
>> I was able to reproduce it easily with multi_v7. Then I commented out
>> dmc bus which fixed the issue. Then I commented out acp and c2c buses
>> (children/passive) which also fixed the issue. Then I uncommented
>> everything and went back to next/dt - exactly the same as it was failing
>> - and since then I cannot reproduce it. I triple checked, but now my
>> multi_v7 on U3 on next/dt boots perfectly fine. Every time.
> 
> This issue still happens from time to time. I quick workaround to fix it 
> is to add:
> 
> MODULE_SOFTDEP("pre: exynos_ppmu");
> 
> to the exynos-bus driver. Is it acceptable solution?

I initially thought it might be caused by deferred probe, but it happens
even in successful boot. I guess we can go with this workaround because
I really do not have other idea.

Best regards,
Krzysztof