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

[Krzysztof Kozlowski]

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.

Best regards,
Krzysztof