January 18, 2023

Kyu networking -- Slow Cache on the Allwinner H3

It is always a bit of a trick when you have two problems. I fixed the first problem (getting the PHY to run at 100 Mbit) only to find out that network transfers were still ridiculously slow. It took a bit of time to convince myself that this now had nothing to do with getting things to run at 100 Mbit and that there was yet another problem.

The other problem turned out to be memcpy. But there is actually nothing wrong memcpy (the same code runs plenty fast on the BBB), but I am convinced that the D cache on the Orange Pi (Allwinner H3) is not really enabled or working.

My attack on this problem is two pronged. Once is that I am taking time to read the ARM documents, which is no small chore. The other is to look at NetBSD startup and cache initialization. I have sometimes begun to wonder if my hardware may be broken, but then I remember that NetBSD can run on the Orange Pi and when it does run, it does a transfer at a proper fast speed.

Have any comments? Questions? Drop me a line!

Kyu / [email protected]