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AMDGPU driver for Linux 6.7 enforces lower power limits from vBIOS

By - | Views: 32,900

Starting with Linux kernel 6.7, users of the AMDGPU driver are not be able to set power limits below the recommended values advised by the AMD Engineering team on the hardware itself. The new low-power limits are intentionally enforced and set based on each card vBIOS specification.

While before the recent 6.7 kernel release the maximum power limit was on-par with what is specified at the vBIOS, but the driver didn't enforce any lower power limits, making the driver really good for fine-tuning it for power saving purposes. However, setting lower power limits that didn't match with what is specified at the vBIOS might harm the GPU as stated on the bug report that lead to this implementation:

This has been discussed on the amd-gfx M/L, and the conclusion was that under-powering outside of the bounding box is potentially dangerous and might damage the hardware. This won't be added back in.

And from the amd-gfx mail list:

The change aligns the driver what has been validated on each board design.  Windows uses the same limits.  Using values lower than the validated range can lead to undefined behavior and could potentially damage your hardware.

The other interesting information extracted from that mail list discussion is that the AMDGPU Linux driver will basically work the same way as the Windows driver, obeying the values stated at vBIOS level.

Opinion: While the changes seem frustrating at first glance for those who want some extra power saving features for computers running on idle, this is an open source driver and it will likely not take long for third party repositories (aur, ppa, copr) to distribute unpatched versions of this module. This already happened in the past with ZFS, NVIDIA, etc. Although, as mentioned, you run the risk of hardware damage if you do decide to use any that pop up.

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I'm and enthusiast of Linux on Laptops and Secure Boot related stuff. Playing exclusively on Linux since 2013. Played on Wine on dates that trace back to 2008(Diablo 2, Lineage 2...). A troubleshooter that used to work with strace and it is now working with Kubernetes...
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Quoting: nwildnerI think that on Laptop usecases the impact will not be THAT big because usuallt the lower voltages are way lower on those dGPUs than they are on Desktop GPUs.

I asked TUXEDO about that, but I don't know if and when they respond. However, I could check it myself, by switching to 6.7 and observing power usage and overall energy outputs.

I think that power limits shouldn't matter that much for hybrid graphic, because dGPU is basically powered down or in some low energy, idle state, which is different from the normal state. However, if those rule apply to iGPU...

On a daily basis, I use 0,6-0,8 kWh/day for office work and media consumption (no gaming). If that will be higher on 6.7, this will be worrying. When gaming, I expect high energy consumption, so that doesn't matter, but I don't game much, so the daily, normal usage is what matters. Of course, current values are small, but if I counted, that my household uses on average 7kWh, 0,8 kWh is ca, 11% of the daily energy consumption and if that would double, that would be 20%, which adds up in a monthly or yearly basis. Not mentioning battery drainage or its quicker usage and fan work because of more heat.

There is a huge difference between my Cool energy profile, where I limit CPU to 0,4-2,6GHz, and the default one, which has no limits (up to 5,1 GHz). On Cool profile, laptop is silent and works normally, while on default, CPU frequency spikes, laptop goes hot and fans become loud - while I see no real gain. This is why I'm worrying that if GPUs become hotter, the culture of work on my laptop will become worse.

Last edited by michaldybczak on 6 March 2024 at 5:49 pm UTC
14 Mar 9
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Is this related to under-volting for crypto mining?
I got answer from TUXEDO:
QuoteIt shouldn't influence, the power profiles for the Sirius 16 Gen1.
If it's causing any problems, we have here a development team which is really quick at fixing issues.
They said nothing about the power draw thou. I guess I have to test it myself.

Last edited by michaldybczak on 10 March 2024 at 8:15 am UTC
I'm on 6.7 and see no changes in power usage, so I guess that has no big influence on laptop or iGPU.
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