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+date = 2024-11-05T23:39:57+01:00
+title = "Adding Zero RPM controls to the RX 7000 series"
+
+[taxonomies]
+tags = ["contrib"]
+
+[extra]
+related = []
++++
+
+Last year I upgraded to an AMD RX 7900XTX, mainly to play Alan Wake II. Just
+like my previous card the XTX has a "Zero RPM" feature: it turns off its fans
+fully if the junction temperature, the hottest part of the GPU, is below a
+certain threshold. With the fans off, the GPU relies on its massive heatsink for
+passive cooling. Even in a very well-ventilated case, however, this will mean
+that the area around the GPU will heat up considerably. For me the fans turn off
+at around 55°C; the component closest to the GPU, an NVMe M.2 SSD, will usually
+slowly heat up to around 48°C whilst idling.
+
+Even under load the SSD never exceeds any temperature threshold, so
+realistically it should be fine, but I'm simply not happy with the amount of
+thermal energy sitting around in there if it could be expelled easily by turning
+on the fans. Worse still, the logic for toggling the fans is not very well
+thought-out, and in the worst case the fans are on for one minute only to be off
+for the next one, ad nauseam.
+
+With my previous GPU turning off the "Zero RPM" was pretty simple. Using the
+[upp(1)](https://github.com/sibradzic/upp) tool you could toggle the feature in
+the GPU's so-called PowerPlay tables. It's a simple job, then, to write a
+systemd service to turn off "Zero RPM" on system boot.
+
+Sadly this is no longer possible on 7000 series cards as there is no more direct
+access to the PowerPlay tables. Instead a new framework using
+[sysfs](https://www.kernel.org/doc/html/latest/filesystems/sysfs.html) for
+managing PowerPlay features was introduced. [Fan
+curve](https://gitlab.freedesktop.org/drm/amd/-/issues/2402) controls were added
+after a while (and a lot of moaning by users), but there was no such knob for
+the "Zero RPM" feature. A couple of months ago a [feature
+request](https://gitlab.freedesktop.org/drm/amd/-/issues/3489) was opened for
+it, but nothing much happened on AMD's side.
+
+Initially hopeful for a reasonably quick resolution, I was getting more and more
+annoyed after a while by the lack of this seemingly simple toggle, so I finally
+caved and proceeded to have a look at it myself. The hardest part was getting
+started with reading
+[amdgpu](https://gitlab.freedesktop.org/agd5f/linux/-/tree/amd-staging-drm-next/drivers/gpu/drm/amd?ref_type=heads)
+code. The code base is absolutely massive and I had no real idea where to start.
+Since fan curve controls already existed I thought it best to find the commit
+that introduced them. After a quick search I found [the relevant
+commit](https://gitlab.freedesktop.org/agd5f/linux/-/commit/eedd5a343d22) and
+had a better understanding of which parts of the code to change.
+
+So, after a while of tweaking and twiddling I had a working prototype and I
+could finally have my GPU run its fans at all times. I knew a lot of people were
+also waiting for this feature, so I [sent a
+patch](https://lists.freedesktop.org/archives/amd-gfx/2024-October/115857.html)
+upstream. After some short feedback and [the addition of another
+feature](https://lists.freedesktop.org/archives/amd-gfx/2024-October/116274.html)
+the series was accepted, and is going to be part of the kernel sometime soon.
+
+With the fans now running at all times I can happily report that ambient
+temperatures have dropped by more than 10°C and the SSD usually does not exceed
+40°C when idling. Even better I do feel quite proud to have finally contributed
+code to the kernel.