Re: Kernel 6.7+ broke under-powering of my RX 6700XT. (Archlinux, mesa/amdgpu)

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Am 21.02.24 um 07:06 schrieb Linux regression tracking (Thorsten Leemhuis):
On 20.02.24 21:18, Alex Deucher wrote:
On Tue, Feb 20, 2024 at 2:41 PM Romano <romaniox@xxxxxxxxx> wrote:
If the increased low range is allowed via boot option, like in proposed
patch, user clearly made an intentional decision. Undefined, but won't
fry his hardware for sure. Undefined is also overclocking in that
matter. You can go out of range with ratio of voltage vs frequency(still
within vendor's limits) for example and crash the system.
This whole thing reminds me of this:
The problem is another module parameter is another interface to
maintain and validate.
Yup, of course, all that is understood.

But we have this "no regressions" rule for a reason. Adhering to it
strictly would afaics be counter-productive in this situation, but give
users some way to manually do what was possible before out-of-the box
IMHO is the minimum we should do.

Maybe just allow that parameter only up to a certain recent GPU
generation, that way you won't have to deal with that at some point in
the future.

  Moreover, we've had a number of cases in the
past where users have under or overclocked and reported bugs or
stability issues and it did not come to light that they were doing
that until we'd already spent a good deal of time trying to debug the
Taint the kernel when that module parameter is used? We iirc have a
taint bit exactly for this sort of situation. Sure, such reports will
still happen, but then you at least have an indicator to spot them.

Let me recap what happened here:

1. AMD is the GPU manufacturer, but apart from a few exceptions doesn't assemble boards.

2. Vendors take AMDs GPUs and assemble them together with power regulators, memory and a bunch of other components into PCIe board.

3. AMD provides a vendor agnostic driver and for this to work vendors describe to the min/max voltage their power regulators can do in some flash memory.

4. Hardware engineers point out that AMDs open source drivers are not respecting the min value.

5. In response a patch was applied to respect that value and not use something outside of the hardware specification the vendor provided.

I'm not sure about it but I think AMD need to respect the min/max values simply by contract and it's not really an option to not do that.

If someone really want to run your hardware outside the vendor recommended values that person can still patch the driver to ignore the limits. It's just that then AMD is not responsible for any damage resulting from that.

So as far as I can see the request to make that a module option is a no-go, especially since hardware engineers have explicitly pointed out that we have to do this in the software stack.


Ciao, Thorsten

  This obviously can still happen if you allow any sort of over
or underclocking, but at least if you stick to the limits you are
staying within the bounding box of the design.


On 2/20/24 19:09, Alex Deucher wrote:
On Tue, Feb 20, 2024 at 11:46 AM Romano <romaniox@xxxxxxxxx> wrote:
For Windows, apps like MSI Afterburner is the one to try and what most
people go for. Using it in the past myself, I would be surprised if it
adhered to such a high min power cap. But even if it did, why would we
have to.

Relying on vendors cap in this case has already proven wrong because
things worked for quite some time already and people reported saving
significant amount of watts, in my case 90W(!) for <10% perf.

Therefore this talk about safety seems rather strange to me and
especially so when we are talking about min_cap. Or name me a single
case where someone fried his card due to "too low power" set in said
variable. Now there was a report, where by going way too low, driver
goes opposite into max power. That's it. That can be easily
detected(vents going crazy etc.) and reverted. It is a max_cap that
protect HW(also above scenario), not a min_cap. Feel free to adhere to
safety standards with that one.
Because operation outside of the design bounding box is undefined.  It
might work for some boards but not others.  It's possible some of the
logic in the firmware or some of the components used on the board may
not work correctly below a certain limit, or the voltage regulators
used on a specific board have a minimum requirement that would not be
an issue if you stick the bounding box.


As for solution, what some suggested already exist - a patch posted by
fililip on gitlab is probably the way most of you would agree. It
introduce a variable that can be set during boot to override min_cap.
But he did not pull requested it, so please, if any one of you who have
access to code and merge kernel would be kind enough to implement it.

On 2/20/24 16:46, Alex Deucher wrote:
On Tue, Feb 20, 2024 at 10:42 AM Linux regression tracking (Thorsten
Leemhuis) <regressions@xxxxxxxxxxxxx> wrote:
On 20.02.24 16:27, Hans de Goede wrote:

On 2/20/24 16:15, Alex Deucher wrote:
On Tue, Feb 20, 2024 at 10:03 AM Linux regression tracking (Thorsten
Leemhuis) <regressions@xxxxxxxxxxxxx> wrote:
On 20.02.24 15:45, Alex Deucher wrote:
On Mon, Feb 19, 2024 at 9:47 AM Linux regression tracking (Thorsten
Leemhuis) <regressions@xxxxxxxxxxxxx> wrote:
On 17.02.24 14:30, Greg KH wrote:
On Sat, Feb 17, 2024 at 02:01:54PM +0100, Roman Benes wrote:
Minimum power limit on latest(6.7+) kernels is 190W for my GPU (RX 6700XT,
mesa, archlinux) and I cannot get power cap as low as before(to 115W),
neither with Corectrl, LACT or TuxClocker and /sys have a variable read-only
even for root. This is not of above apps issue but of the kernel, I read
similar issues from other bug reports of above apps. I downgraded to v6.6.10
kernel and my 115W(under power)cap work again as before.
For the record and everyone that lands here: the cause is known now
(it's 1958946858a62b ("drm/amd/pm: Support for getting power1_cap_min
value") [v6.7-rc1]) and the issue afaics tracked here:

Other mentions:

Haven't seen any statement from the amdgpu developers (now CCed) yet on
this there (but might have missed something!). From what I can see I
assume this will likely be somewhat tricky to handle, as a revert
overall might be a bad idea here. We'll see I guess.
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.
Thx for the reply! Yeah, I was expecting something along those lines.

Nevertheless it afaics still is a regression in the eyes of many users.
I'm not sure how Linus feels about this, but I wonder if we can find
some solution here so that users that really want to, can continue to do
what was possible out-of-the box before. Is that possible to realize or
even supported already?

And sure, those users would be running their hardware outside of its
specifications. But is that different from overclocking (which the
driver allows, doesn't it? If not by all means please correct me!)?
Sure.  The driver has always had upper bound limits for overclocking,
this change adds lower bounds checking for underclocking as well.
When the silicon validation teams set the bounding box for a device,
they set a range of values where it's reasonable to operate based on
the characteristics of the design.

If we did want to allow extended underclocking, we need a big warning
in the logs at the very least.
Requiring a module-option to be set to allow this, as well as a big
warning in the logs sounds like a good solution to me.
Yeah, especially as it sounds from some of the reports as if some
vendors did a really bad job when it came to setting the proper
lower-bound limits are now adhered -- and thus higher then what we used
out-of-the box before 1958946858a62b was applied.

Side note: I assume those "lower bounds checking" is done round about
the same way by the Windows driver? Does that one allow users to go
lower somehow? Say after modifying the registry or something like that?
Or through external tools?
Windows uses the same limit.  I'm not aware of any way to override the
limit on windows off hand.


Ciao, Thorsten

Roman posted something that apparently was meant to go to the list, so
let me put it here:

UPDATE: User fililip already posted patch, but it need to be merged,
discussion is on gitlab link below.

(PS: I hope I am replying correctly to "all" now? - using original addr.)

it seems that commit was already found(see user's 'fililip' comment):
commit 1958946858a62b6b5392ed075aa219d199bcae39
Author: Ma Jun <Jun.Ma2@xxxxxxx>
Date:   Thu Oct 12 09:33:45 2023 +0800

       drm/amd/pm: Support for getting power1_cap_min value

       Support for getting power1_cap_min value on smu13 and smu11.
       For other Asics, we still use 0 as the default value.

       Signed-off-by: Ma Jun <Jun.Ma2@xxxxxxx>
       Reviewed-by: Kenneth Feng <kenneth.feng@xxxxxxx>
       Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>

However, this is not good as it remove under-powering range too far. I
was getting only about 7% less performance but 90W(!) less consumption
when set to my 115W before. Also I wonder if we as a OS of options and
freedom have to stick to such very high reference for min values without
ability to override them through some sys ctrls. Commit was done by amd
guy and I wonder if because of maybe this post that I made few months
ago(business strategy?):
This is not a dangerous OC upwards where I can understand desire to
protect HW, it is downward, having min cap at 190W when card pull on
115W almost same speed is IMO crazy to deny. We don't talk about default
or reference values here either, just a move to lower the range of
options for whatever reason.
I don't know how much power you guys have over them, but please
consider either reverting this change, or give us an option to set
min_cap through say /sys (right now param is readonly, even for root).
Thank you in advance for looking into this, with regards:  Romano

And while at it, let me add this issue to the tracking as well

[TLDR: I'm adding this report to the list of tracked Linux kernel
regressions; the text you find below is based on a few templates
paragraphs you might have encountered already in similar form.
See link in footer if these mails annoy you.]

Thanks for the report. To be sure the issue doesn't fall through the
cracks unnoticed, I'm adding it to regzbot, the Linux kernel regression
tracking bot:

#regzbot introduced 1958946858a62b /
#regzbot title drm: amdgpu: under-powering broke

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
Everything you wanna know about Linux kernel regression tracking:
That page also explains what to do if mails like this annoy you.

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