Re: [PATCH v2] arm64: dts: rockchip: fix rk3328-roc-cc gmac2io tx/rx_delay

["Leonidas P. Papadakos" <papadakospan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Στις Κυρ, 10 Μαρ, 2019 at 2:26 ΠΜ, ο/η "Leonidas P. 
Papadakos" <papadakospan@gmail.com> έγραψε:
>>  > > We have several issues on the rk3328.
>>  > >
>>  > > The first issue, which you describe as the ssh lag, is the
>>  > > tx-offload issue.
>>  > > Packets that are larger than the MTU and will be fragmented 
>> break if
>>  > > tx-offload is enabled.
>>  > > To fix this, you must somehow disable tx-offload.
>>  > > force-thresh-dma-mode disabled tx-offload, but had other side 
>> effects.
>>  > > Ayufan's patch disables tx-offload only if the packet is larger 
>> than
>>  > > 1498.
>>  > > You can also disable tx-offload from userspace with ethtool.
>>  > >
>>  > > The second issue is the high rate of tx packets being corrupted,
>>  > > which my patch to set the tx pull values fixes.
>>  > >
>>  > > The third issue is the tx and rx delays need to be tuned now 
>> that
>>  > > the tx packet corruption issue has been fixed.
>>  > >
>>  > > I hope this clears things up a little for you.
>>  >
>>  > Yup, that's what I have in my mind already. My previous comment 
>> wasn't
>>  > clear, I know.
>>  > I pieced it together after your dma-mode patch, because that one 
>> fixed
>>  > the ssh lag.
>>  > My previous email was just what I saw after those changes.
>>  >
>>  > In my case the link reset still happens with your patch.
>>  >
>>  > You're thinking that the combination of your patch, ayufan's
>>  > "conditional" patch and a specific tweak in the delays would work 
>> for
>>  > the network instability problem?
>>  >
>> 
>>  Correct, the link-reset tends to happen when the delays are at the 
>> edge of
>>  working.
>>  There is also the possibility that board level manufacturing 
>> tolerances are
>>  causing issues where the delay can change between boards.
>>  If this is the case, we will have to make an auto-tune function, 
>> probably
>>  based off the mmc version.
> 
> So, I tried just your patch with archlinuxARM linux 5.0
> (meaning the tx/rx_delays are 0x25/0x11 respectively if I'm not 
> mistaken)
> and disabled tx offload through ethtool.
> 
> After 3 30-second iperf3 tests, no link resets! I get about the same 
> speed you mentioned before,
> 800-something to 700-something lowest.
> 
> Seems like the delays that are already there in the dts are better 
> than the ones I picked up from the Armbian dts.
> 
> It's worth noting that I've never noticed a link reset in my ~3 
> months of using the 4.4 Rockchip kernel
> that Armbian packages using ayufan's linux-kernel repo. Maybe 
> something there?
> 
> All in all, it does seem to be much better with your patch.

I've been trying to reach ayufan about his patch, getting is into 
mainline:
https://github.com/ayufan-rock64/linux-mainline-kernel/commit/41eeb7cd789ea7cac0cbf4b35b53055f354da757

but it seems he's not responding. I'll cc him.
His patch would be a really cool fix if it could be in 5.1, or even 5.2,
as a replacement to force_thresh_dma_mode



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