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Date:   Fri, 05 Apr 2019 21:38:57 +0300
From:   "Leonidas P. Papadakos" <papadakospan@gmail.com>
Subject: Re: [PATCH 1/2] stmmac: introduce flag to dynamically disable TX
 offload for rockchip devices
To:     Robin Murphy <robin.murphy@arm.com>
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> What's your overall setup? So far with my RK3328 box I've found that 
> with an IPv4 link and an MTU of 2000 I have to dial PBL right down to 
> 1 or 2 (with no-pbl-x8 as well) to prevent Tx stalling, and with the 
> MTU bumped up to 3000 it just won't play at any PBL setting...
> 
> Robin.

I'm using a Libre Computer Renegade with RK3328 SoC(maybe it's a board 
specific thing?)
I'm using txpbl as from what I can gather, the rx has no issues, no 
need to change it.

When it comes to rx,
running the server (iperf3 -s) on the Renegade and iperf3 -c 
<renegade_ip> on my laptop,
I get about 940 Mbps. It's always been like that, satisfactory.

When it comes to tx (the one all the fuss is about)
I eventually find that just with snps,txpbl = <0x21>, and no other pbl 
thing set I get about 905 Mbps on average sent to my laptop, now 
running the iperf3 server.

I must say I haven't touched the MTUs but I never needed to as the 
issue presented itself in normal usage. Simple iperf tests will fail 
after same kilobytes if no tweaks are applied.