On Thu, Dec 12, 2019 at 8:21 AM Peter Geis <pgwipeout@xxxxxxxxx> wrote: > > Good Morning, > > So I've continued work on fixing the rk3328/rk3399 gmac mtu tx coe offload bug. > I've found two fixes that maintain full performance and work consistently. > > First, is ayufan's tx coe patch [0], which takes the bugged_jumbo > concept introduced in [1] and applies it to 1498 and above, vice 1500 > and above. > > The only downside is this disables tx coe for full size packets, which > has a negligible performance impact in my testing. > > The other option I've found that reliably works is bringing the mtu > down to 1498. > This allows tx coe to remain enabled, but with the downside of total > loss of jumbo frames. > The reduction in size has a negligible performance impact in my testing. Shortly after sending this I discovered that setting the mtu lower is not sufficient in some corner cases. I managed to make offload break even at a 1496 mtu by `apt install kubuntu-desktop` over ssh on a gigabit internet connection. After porting ayufan's patch the issue went away. So unless we can fix this by axi tuning, his patch seems to be the most viable option. > > I have also discovered that the rockchip implementation of the stmmac > driver does not process flags such as max-frame-size. > > A third option, which I haven't explored because I don't know enough > about how it works, is possibly tuning the axi settings, via the > snps,axi-config and snps,mtl-tx-config handles. > I don't know if this is feasible, but since tuning the dma settings > affects the rk3328 I have hope. > I do know that my current fix for the rk3328 does not provide full > performance and does not work at all on the rk3399. > > Thoughts? > > [0] https://github.com/ayufan-rock64/linux-kernel/commit/8a41c672dd77e48b06c1b2dec3aa9db4bad30b49#diff-c897c0b53bd633240f4b12c4d29a5ff1 > [1] https://github.com/torvalds/linux/commit/ebbb293f8b3021ae2009fcb7cb3b8a52fb5fd06a _______________________________________________ Linux-rockchip mailing list Linux-rockchip@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/linux-rockchip
