stmmac/RTL8211F/Meson GXBB: TX throughput problems

Martin Blumenstingl martin.blumenstingl at
Mon Sep 12 14:26:38 PDT 2016

Hi Alexandre,

On Mon, Sep 12, 2016 at 6:37 PM, Alexandre Torgue
<alexandre.torgue at> wrote:
> Which Synopsys IP version do you use ?
found this in a dmesg log:
[    1.504784] stmmac - user ID: 0x11, Synopsys ID: 0x37
[    1.509785]  Ring mode enabled
[    1.512796]  DMA HW capability register supported
[    1.517286]  Normal descriptors
[    1.520565]  RX Checksum Offload Engine supported
[    1.525219]  COE Type 2
[    1.527638]  TX Checksum insertion supported
[    1.531862]  Wake-Up On Lan supported
[    1.535483]  Enable RX Mitigation via HW Watchdog Timer
[    1.543851] libphy: stmmac: probed
[    1.544025] eth0: PHY ID 001cc916 at 0 IRQ POLL (stmmac-0:00) active
[    1.550321] eth0: PHY ID 001cc916 at 7 IRQ POLL (stmmac-0:07)

>> Gbit ethernet on my device is provided by a Realtek RTL8211F RGMII PHY.
>> Similar issues were reported in #linux-amlogic by a user with an
>> Odroid C2 board (= similar hardware).
>> The symptoms are:
>> Receiving data is plenty fast (I can max out my internet connection
>> easily, and with iperf3 I get ~900Mbit/s).
>> Transmitting data from the device is unfortunately very slow, traffic
>> sometimes even stalls completely.
>> I have attached the iperf results and the output of
>> /sys/kernel/debug/stmmaceth/eth0/descriptors_status.
>> Below you can find the ifconfig, netstat and stmmac dma_cap info
>> (*after* I ran all tests).
>> The "involved parties" are:
>> - Meson GXBB specific network configuration registers (I have have
>> double-checked them with the reference drivers: everything seems fine
>> here)
>> - stmmac: it seems that nobody else has reported these kind of issues
>> so far, however I'd still like to hear where I should enable some
>> debugging bits to rule out any stmmac bug
> On my side, I just tested on the same "kind" of system:
> -RTL8211EG as PHY
> With I perf, I reach:
>         -RX: 932 Mbps
>         -TX: 820Mbps
> Can you check ethtool -S eth0 (most precisely "MMC"counter and errors) ?
> Which kernel version do you use ?
I am using a 4.8.0-rc4 kernel, based on Kevin's "integration" branch: [0]
Unfortunately I don't have access to my device in the next few days,
but I'll keep you updated once I have the ethtool output.

Thanks for your time


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