netdev - Re: stmmac/RTL8211F/Meson GXBB: TX throughput problems

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Date:   Mon, 12 Sep 2016 18:37:49 +0200
From:   Alexandre Torgue <alexandre.torgue@...com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        <netdev@...r.kernel.org>, <linux-amlogic@...ts.infradead.org>
CC:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Johnson Leung <r58129@...escale.com>
Subject: Re: stmmac/RTL8211F/Meson GXBB: TX throughput problems

Hi Martin,


On 09/11/2016 10:39 PM, Martin Blumenstingl wrote:
> Hello,
>
> I have a device with a Meson GXBB SoC with an stmmac IP block.

Which Synopsys IP version do you use ?

> 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:
-SYNOPSYS GMAC 3.7
-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 ?

Regards

Alex




> - RTL8211F PHY driver: unfortunately there are no public datasheets
> available so this is hard to debug. but I'm guessing that TX delay
> could cause similar issues, so this may be the cause as well.
>
>
> Thanks for any input in advance!
> Regards,
> Martin
>
>
> [root@...rm ~]# ifconfig eth0
> eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>         inet 192.168.1.235  netmask 255.255.255.0  broadcast 192.168.1.255
>         ether e2:aa:53:fc:f5:c5  txqueuelen 1000  (Ethernet)
>         RX packets 1967602  bytes 2968750265 (2.7 GiB)
>         RX errors 0  dropped 0  overruns 0  frame 0
>         TX packets 101875  bytes 8548285 (8.1 MiB)
>         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
>         device interrupt 18
>
> [root@...rm ~]# netstat -i
> Kernel Interface table
> Iface      MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
> eth0      1500  1967801      0      0 0        101934      0      0      0 BMRU
>
> [root@...rm ~]# cat /sys/kernel/debug/stmmaceth/eth0/dma_cap
> ==============================
>         DMA HW features
> ==============================
>         10/100 Mbps Y
>         1000 Mbps Y
>         Half duple Y
>         Hash Filter: Y
>         Multiple MAC address registers: Y
>         PCS (TBI/SGMII/RTBI PHY interfatces): N
>         SMA (MDIO) Interface: Y
>         PMT Remote wake up: Y
>         PMT Magic Frame: Y
>         RMON module: Y
>         IEEE 1588-2002 Time Stamp: N
>         IEEE 1588-2008 Advanced Time Stamp:N
>         802.3az - Energy-Efficient Ethernet (EEE) Y
>         AV features: N
>         Checksum Offload in TX: Y
>         IP Checksum Offload (type1) in RX: N
>         IP Checksum Offload (type2) in RX: Y
>         RXFIFO > 2048bytes: Y
>         Number of Additional RX channel: 0
>         Number of Additional TX channel: 0
>         Enhanced descriptors: N
>