Re: Fwd: PCI: Loongson: 8b3517f88ff2 breaks PCIe on some system

[Thorsten Leemhuis]

On 23.07.23 04:03, Bagas Sanjaya wrote:
> 
> I notice a regression report on Bugzilla [1]. Quoting from it:
> 
>> After 8b3517f88ff2 ("PCI: loongson: Prevent LS7A MRRS increases") backported to stable, we have received multiple regression reports including one from Debian build farm[1] that some systems failed to initialize some PCIe devices.
>>
>> I was able to reproduce on one of my Loongson-3A4000+7A system. It seems like the root cause is firmware on those systems didn't set MRRS properly but 8b3517f88ff2 ("PCI: loongson: Prevent LS7A MRRS increases") assumed firmware's maximum MRRS is always valid.
>>
>> [1]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1035587
> 
> See Bugzilla for the full thread.
> 
> The linked Debian BTS entry have debugging details on this regression
> (boot log, cpuinfo, and lspci).
> 
> Anyway, I'm adding this regression to regzbot:
> 
> #regzbot introduced: 8b3517f88ff298 https://bugzilla.kernel.org/show_bug.cgi?id=217680
> #regzbot title: LS7A MRRS quirk fails to initialize PCIe devices
> #regzbot link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1035587

FWIW & TWIMC, a fix for this is in the works already afaics:

#regzbot monitor:
https://lore.kernel.org/all/20230718133259.2867432-1-jiaxun.yang@xxxxxxxxxxx/
#regzbot fix: pci: loongson: Workaround MIPS firmware MRRS settings

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
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