[Linux] Freezes &#111;n Asrock X370 Taichi + C6 enabled

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Posted: 26 Feb 2018 at 2:35am

Just for the reference, most likely the fault is with the CPU, not with motherboard or RAM.

See: https://bugzilla.kernel.org/show_bug.cgi?id=196683

So far AMD didn't fix it with any firmware updates.

Edited by shmerl - 26 Feb 2018 at 2:38am

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Posted: 01 Mar 2018 at 2:46am

So, these freezes aren't related to RAM after all. It's apparently something to do with how C6 states are handled.

See:

https://bugzilla.kernel.org/show_bug.cgi?id=196683
https://community.amd.com/message/2848556#comment-2848556

For now, I built a custom kernel as a workaround (with CONFIG_RCU_NOCB_CPU), and set rcu_nocbs=0-15 parameter, but it really means that CPU is defective or at least doesn't handle power states properly.

AMD answered this to similar support request:

This issue has been fixed with the latest BIOS updates, but the option to fix it may not be available in all BIOS.
...
I request you to update to the latest BIOS and see if you have the Power Supply Control option in the MB BIOS. Try toggling this option between the different settings to see if it fixes it. If the specific option is not available I would suggest you keep C6 off for now.

Latest ASRock firmware update doesn't seem to contain this fix. Can anyone from ASRock please confirm, if this fix is eventually coming to your firmware too?

Edited by shmerl - 01 Mar 2018 at 2:52am

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Posted: 01 Mar 2018 at 4:22am

shmerl,this is a user forum and seldom do ASRock people post here. I would suggest you open an ASRock support ticket and ask them. I also suggest you ask AMD (AMD support ticket) and ask them to specify a SPECIFIC AGESA/UEFI/MICRODE that corrects this problem. Latest tells me nothing especially with the way AMD and ASRock release code. Please let us hear how you make out. Thanks and enjoy, John.

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Posted: 01 Mar 2018 at 6:16am

AFAIK enabling Cool'n'Quiet and/or C6 would make your Linux freeze. Same happens to me, but it looks like ASRock has nothing to do with it - it's a problem somewhere between the Ryzen CPU and Linux kernel. There are multiple bug reports about this issue and even software to mitigate it - http://github.com/qrwteyrutiyoup/ryzen-stabilizator .

Also some Ryzen CPUs segfault when you are compiling heavy software, and these can be RMA'd, as it is a recognized issue.

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Posted: 01 Mar 2018 at 6:19am

I had the segfault issue and already RMA'd the CPU. Many report, that replacements are actually more likely to get the C6 freeze bug. Disabling C6 though is a very crude workaround for these freezes. Using CONFIG_RCU_NOCB_CPU and rcu_nocbs=0-15 is a better one.

Personally, I consider buying Ryzen 2 which hopefully won't have this problem anymore (but can have new ones, haha). And thanks for the suggestions, I'll contact ASRock support directly about it.

Edited by shmerl - 01 Mar 2018 at 6:24am

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Posted: 04 Mar 2018 at 8:29am

Browsing around my firmware settings, I found this one:

Advanced > AMD CBS > Zen Common Options > Power Supply Idle Control.

I changed it from auto to low, let's see if it will help with stock kernel.

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Posted: 04 Mar 2018 at 12:14pm

Still freezing with "low current idle". Testing now with "common current idle".

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Posted: 05 Mar 2018 at 2:30am

I'm now also seeing this in dmesg:

[11225.078807] x86: Booting SMP configuration:
[11225.078808] smpboot: Booting Node 0 Processor 1 APIC 0x1
[11225.081035] [Firmware Bug]: ACPI MWAIT C-state 0x0 not supported by HW (0x0)
[11225.081063]  cache: parent cpu1 should not be sleeping
[11225.081127] microcode: CPU1: patch_level=0x08001129
[11225.081213] CPU1 is up
[11225.081233] smpboot: Booting Node 0 Processor 2 APIC 0x2

And so on for all 16 virtual cores.

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Posted: 07 Mar 2018 at 9:07am

That C-state 0x0 not supported by HW happens now always, so it's not related to my test above.

With Advanced > AMD CBS > Zen Common Options > Power Supply Idle Control set to "Common current idle" (instead of auto), I didn't get any freezes in a while, so I assume it's a valid workaround.

I noticed what changes after it's set in the firmware, using zenstates.py:

When set to auto (freezes happen):

C6 State - Package - Enabled
C6 State - Core - Enabled

when set to Common current idle (no freezes so far):

C6 State - Package - Disabled
C6 State - Core - Enabled

So apparently it disables package C6 state (while keeping core C6 state enabled)! Hopefully it can shed some light on what the problem is. I wonder if Ryzen 2 will be free of this issue.

What exactly is "package" in this context? Is it still part of CPU, or it's something on the motherboard?

Edited by shmerl - 07 Mar 2018 at 9:19am

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