[net-next PATCH v1 0/2] stmmac: dwmac-meson8b: configurable RGMII TX delay

[Martin Blumenstingl]

Currently the dwmac-meson8b stmmac glue driver uses a hardcoded 1/4
cycle TX clock delay. This seems to work fine for many boards (for
example Odroid-C2 or Amlogic's reference boards) but there are some
others where TX traffic is simply broken.
There are probably multiple reasons why it's working on some boards
while it's broken on others:
- some of Amlogic's reference boards are using a Micrel PHY
- hardware circuit design
- maybe more...

This raises a question though:
Which device is supposed to enable the TX delay when both MAC and PHY
support it? And should we implement it for each PHY / MAC separately
or should we think about a more generic solution (currently it's not
possible to disable the TX delay generated by the RTL8211F PHY via
devicetree when using phy-mode "rgmii")?

iperf3 results on my Mecool BB2 board (Meson GXM, RTL8211F PHY) with
TX clock delay disabled on the MAC (as it's enabled in the PHY driver).
TX throughput was virtually zero before:
$ iperf3 -c 192.168.1.100 -R          
Connecting to host 192.168.1.100, port 5201
Reverse mode, remote host 192.168.1.100 is sending
[  4] local 192.168.1.206 port 52828 connected to 192.168.1.100 port 5201
[ ID] Interval           Transfer     Bandwidth
[  4]   0.00-1.00   sec   108 MBytes   901 Mbits/sec                  
[  4]   1.00-2.00   sec  94.2 MBytes   791 Mbits/sec                  
[  4]   2.00-3.00   sec  96.5 MBytes   810 Mbits/sec                  
[  4]   3.00-4.00   sec  96.2 MBytes   808 Mbits/sec                  
[  4]   4.00-5.00   sec  96.6 MBytes   810 Mbits/sec                  
[  4]   5.00-6.00   sec  96.5 MBytes   810 Mbits/sec                  
[  4]   6.00-7.00   sec  96.6 MBytes   810 Mbits/sec                  
[  4]   7.00-8.00   sec  96.5 MBytes   809 Mbits/sec                  
[  4]   8.00-9.00   sec   105 MBytes   884 Mbits/sec                  
[  4]   9.00-10.00  sec   111 MBytes   934 Mbits/sec                  
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.00  sec  1000 MBytes   839 Mbits/sec    0             sender
[  4]   0.00-10.00  sec   998 MBytes   837 Mbits/sec                  receiver

iperf Done.
$ iperf3 -c 192.168.1.100   
Connecting to host 192.168.1.100, port 5201
[  4] local 192.168.1.206 port 52832 connected to 192.168.1.100 port 5201
[ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
[  4]   0.00-1.01   sec  99.5 MBytes   829 Mbits/sec  117    139 KBytes       
[  4]   1.01-2.00   sec   105 MBytes   884 Mbits/sec  129   70.7 KBytes       
[  4]   2.00-3.01   sec   107 MBytes   889 Mbits/sec  106    187 KBytes       
[  4]   3.01-4.01   sec   105 MBytes   878 Mbits/sec   92    143 KBytes       
[  4]   4.01-5.00   sec   105 MBytes   882 Mbits/sec  140    129 KBytes       
[  4]   5.00-6.01   sec   106 MBytes   883 Mbits/sec  115    195 KBytes       
[  4]   6.01-7.00   sec   102 MBytes   863 Mbits/sec  133   70.7 KBytes       
[  4]   7.00-8.01   sec   106 MBytes   884 Mbits/sec  143   97.6 KBytes       
[  4]   8.01-9.01   sec   104 MBytes   875 Mbits/sec  124    107 KBytes       
[  4]   9.01-10.01  sec   105 MBytes   876 Mbits/sec   90    139 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bandwidth       Retr
[  4]   0.00-10.01  sec  1.02 GBytes   874 Mbits/sec  1189             sender
[  4]   0.00-10.01  sec  1.02 GBytes   873 Mbits/sec                  receiver

iperf Done.


Martin Blumenstingl (2):
  net: dt-bindings: add RGMII TX delay configuration to meson8b-dwmac
  net: stmmac: dwmac-meson8b: make the RGMII TX delay configurable

 Documentation/devicetree/bindings/net/meson-dwmac.txt | 11 +++++++++++
 drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c   | 16 +++++++++++-----
 include/dt-bindings/net/dwmac-meson8b.h               | 18 ++++++++++++++++++
 3 files changed, 40 insertions(+), 5 deletions(-)
 create mode 100644 include/dt-bindings/net/dwmac-meson8b.h

-- 
2.10.2