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Subject[PATCH 0/3] Meson8b/8m2: Ethernet RGMII TX delay fixes
Date
The Ethernet TX performance has been historically bad on Meson8b and
Meson8m2 SoCs because high packet loss was seen. Today I (presumably)
found out why this is: the input clock (which feeds the RGMII TX clock)
has to be at least 4 times 125MHz. With the fixed "divide by 2" in the
clock tree this means that m250_div needs to be at least 2.

Now the PRG_ETH0 register in Linux matches what u-boot and the vendor
3.10 kernel use. iperf3 output on my Odroid-C1 (where this series has
been tested):
# iperf3 -c 192.168.1.100
Connecting to host 192.168.1.100, port 5201
[ 5] local 192.168.1.163 port 42636 connected to 192.168.1.100 port 5201
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 105 MBytes 878 Mbits/sec 0 609 KBytes
[ 5] 1.00-2.00 sec 106 MBytes 885 Mbits/sec 0 683 KBytes
[ 5] 2.00-3.09 sec 73.7 MBytes 570 Mbits/sec 0 683 KBytes
[ 5] 3.09-4.00 sec 81.9 MBytes 754 Mbits/sec 0 795 KBytes
[ 5] 4.00-5.00 sec 104 MBytes 869 Mbits/sec 0 877 KBytes
[ 5] 5.00-6.00 sec 105 MBytes 878 Mbits/sec 0 877 KBytes
[ 5] 6.00-7.00 sec 68.0 MBytes 571 Mbits/sec 0 877 KBytes
[ 5] 7.00-8.00 sec 80.7 MBytes 676 Mbits/sec 0 877 KBytes
[ 5] 8.00-9.01 sec 102 MBytes 853 Mbits/sec 0 877 KBytes
[ 5] 9.01-10.00 sec 101 MBytes 859 Mbits/sec 0 877 KBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 927 MBytes 778 Mbits/sec 0 sender
[ 5] 0.00-10.01 sec 927 MBytes 777 Mbits/sec receiver


@David: please only apply patch #1 from this series. I included the .dts
changes so others can test them together with the driver update (as the
.dts has to be updated to fully fix the TX packet loss - with the old TX
delay in the .dts there is still packet loss, even with a fixed driver).

I will ask Kevin to apply patches #2 and #3 through his linux-amlogic
tree - or resend them. When applying the .dts patches without the fix in
the driver then I get 100% packet loss on my Odroid-C1. So unfortunately
there's a hard dependency between patch 1 and 2/3.


Martin Blumenstingl (3):
net: stmmac: dwmac-meson8b: Fix the RGMII TX delay on Meson8b/8m2 SoCs
ARM: dts: meson8b: odroidc1: use the same RGMII TX delay as u-boot
ARM: dts: meson8m2: mxiii-plus: use the same RGMII TX delay as u-boot

arch/arm/boot/dts/meson8b-odroidc1.dts | 2 +-
arch/arm/boot/dts/meson8m2-mxiii-plus.dts | 2 +-
.../net/ethernet/stmicro/stmmac/dwmac-meson8b.c | 14 +++++++++++---
3 files changed, 13 insertions(+), 5 deletions(-)

--
2.24.1

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