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Quartex: Mali GPU glitches

February 20, 2019 Leave a comment Go to comments

EDIT: I did further testing after this article was written, and believe the source of this to be about heat. Even with extra fans, running games like Tyrian (asm.js) that are extremely demanding, plus resizing a graphics intensive windows constantly, the temperature reached 71 degrees C very quickly. And this was with two cabinet fans helping the built-in fan to cool the device. It is thus not unthinkable that when running solo (no extra fans) that the kernel shut the device down to not cook the chipset. Which also explains why the device wont boot properly afterwards (the device is still hot).

Glitches

Something really strange is happening on Chrome and Firefox for ARM. JavaScript is not supposed to be able to take down a system, and in this case it’s neither an attempt as such either — yet for some reason I have managed to take down the ODroid XU4 with both Chrome and Firefox lately.

ODroid XU4

I guess I should lead with that I’m not able to replicate this on x86. One of the things I really love about the ODroid XU4 is that it’s affordable, powerful and probably the only SBC I have used that runs stable on the mali GPU. As you probably know I tested at least 10 different SBC’s back in 2018, and whenever there was a mali GPU involved, the product was either haunted by instabilities or lacked drivers all together.

amibian

Since the codebase for Chrome (and I presume Firefox) is ultimately the same between platforms, it leaves a question-mark about the ODroid. It is by far the most stable SBC I have tested so far (except for the PI, which is sadly underpowered for this task), but stable doesn’t mean flawless. And to be honest, Amibian.js is pushing web tech to the very limits.

Not Mali again

The reason I suspect the mali to be the culprit behind all this, is because the “bug” if we can call it that, happens exclusively during resize. So if there is a lot going on inside a desktop-window, you can sometimes provoke the ODroid to cold-crash and reboot. You actually have to power the board down and switch it back on for it to boot properly.

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Cloudripper ~ 5x ODroid XU4 [40 cores] in a PICO 5h cube

The resize and moving of windows uses CSS transformation, which in modern browsers makes use of the GPU. Chrome talks directly with OpenGL (or glES), so the operations are proxied through that. And again, since OpenGL is pretty rock solid elsewhere, we are only left with one common denominator: the mali GPU.

The challenge is that there is no way to debug or catch this error, because when it occurs the whole system literally goes down. There is no exception thrown, nor is the browser process terminated (not even a log entry, so it’s a clean-cut) — the system reboots on the spot. Since it fails on reboot when opening X (setting a screen-mode) I again point the finger at the GPU. Somehow a flag or lock survives the cold-reboot and that’s why you have to manually switch it off and on again.

This is the exact problem that made the NanoPI Fire useless. It only shipped with Android embedded drivers. The X drivers could hardly open a display without crashing. Such a waste of a good cpu.

x86 as head

ODroid is perfect for a low-cost Amibian.js experience, but I was unsure if it would handle the payload. Interestingly it handles it just fine and even with a high-speed action game running + background tasks we are not using 50% of the CPU even.

Ram is holding up too, with memory consumption while running Tyrian + having a few graphics viewers open, is at a reasonable 700 mb (of 2 gigabyte in total).

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Tyrian jogs along at 45 fps ~ that is not bad for a $45 SBC

Right now this strange error is rare, but if it continues or grows into a problem (chrome is hardly useable at all, only firefox) then I have no option than to replace the master sbc in the cluster with something else. The x86 UP board is more than capable, but it would be a shame to break the price range because of that (excuse my language) crap mali GPU. I honestly don’t understand why board makers insist on using a mali. Every board that has a mali is haunted by problems and get poor reviews.

It will be exciting to check out the dragonboard, although I fear 1Gb memory will not be enough for smooth operation. Not without a sata interface and a good swap-file.

Android and Delphi

One alternative is to switch to Android and use Delphi to code a custom Chromium Embedded webview. I am hoping to avoid the overhead of Android, but Delphi would definitively be a bonus with Android embedded (“Android of things”).

We will see.

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