Ping latency raises after a while on Phicomm N1 running Armbian 5.67 (4.19 kernel)

Update: The patch mentioned in this post has been merged and I suppose it will be part of Linux 5.0. Phicomm N1’s dtb has also been merged into Linux 5.0. Therefore I suggest you to upgrade the kernel you’re using if you have the problem described in this post, instead of using the dtb I attached at the end of the post. Of course, the dtb should Just Work ™ if you just don’t want to upgrade your kernel.

Not sure if it’s fixed yet, I’m still testing it. But the patch looks promising. Update: I believe it works.

I was led to the patch by sheepman’s message on IRC, through D4T’s post, and finally reached Carlo’s patch. Credits to them, really appreciated.

According to the patch, it’s a BUG in the device tree, which used a wrong IRQ type for RTL8211F. Consequently, (I think) the kernel is losing interrupts and thus not able to process incoming packets timely.

After checking the constants here, I patched the DTB I’m using accordingly:

The compiled one is also available (with the fix for USB):

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