Getting 8139too to work at 100 Mbps Full Duplex

I recently switched to my RTL-8139 NIC instead of default onboard Intel NIC, after I came to know that e100 uses binary blobs. I’ve a Netgear WGT624 WiFi router (acting as switch, atm). I plug-in my desktop at a 100 Mbps switch port in the switch. So now when I connected my RTL8139 NIC to my wireless enabled wired-switch, it comes online at 10 Mbps (full-duplex)

abbe@chateau ~ $ sudo ethtool rl0
Settings for rl0:
        Supported ports: [ TP MII ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
        Advertised auto-negotiation: No
        Speed: 10Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 32
        Transceiver: internal
        Auto-negotiation: off
        Supports Wake-on: pumbg
        Wake-on: p
        Current message level: 0x00000007 (7)
        Link detected: yes

Now, I tried manually switching it 100 Mbps (full-duplex):

abbe@chateau ~ $ sudo ethtool -s rl0 speed 10
abbe@chateau ~ $ sudo ethtool rl0
Settings for rl0:
        Supported ports: [ TP MII ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
        Advertised auto-negotiation: No
        Speed: 100Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 32
        Transceiver: internal
        Auto-negotiation: off
        Supports Wake-on: pumbg
        Wake-on: p
        Current message level: 0x00000007 (7)
        Link detected: yes

Now, to automate this, I added following line into /etc/modprobe.d/options and executed update-modules.

abbe@chateau ~ $ cat /etc/modprobe.d/options
options 8139too media=0x231
abbe@chateau ~ $ sudo modprobe -r 8139too
abbe@chateau ~ $ sudo update-modules
 * Updating /etc/modprobe.conf by hand ...                                                                                                                                 [ ok ]
 * Updating modules.dep ...                                                                                                                                                [ ok ]
abbe@chateau ~ $ sudo modprobe 8139too
abbe@chateau /etc/modprobe.d $ sudo /usr/sbin/ethtool rl0
Settings for rl0:
        Supported ports: [ TP MII ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
        Advertised auto-negotiation: No
        Speed: 100Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 32
        Transceiver: internal
        Auto-negotiation: off
        Supports Wake-on: pumbg
        Wake-on: p
        Current message level: 0x00000007 (7)
        Link detected: yes

How to arrive at the number 0×231, check out modinfo 8139too and drivers/net/8139too.c source code. BtW, I just noticed that rl0 has auto-negotiation off, so I decided to turn it on, and following are the results:

abbe@chateau ~ $ sudo ethtool -s rl0 autoneg on
abbe@chateau ~ $ sudo ethtool rl0 
Settings for rl0:
        Supported ports: [ TP MII ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
        Advertised auto-negotiation: Yes
        Speed: 10Mb/s
        Duplex: Half
        Port: MII
        PHYAD: 32
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: pumbg
        Wake-on: p
        Current message level: 0x00000007 (7)
        Link detected: no
abbe@chateau ~ $ sudo ethtool -s rl0 speed 100 duplex full
abbe@chateau ~ $ sudo ethtool rl0 
Settings for rl0:
        Supported ports: [ TP MII ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
        Advertised auto-negotiation: Yes
        Speed: 100Mb/s
        Duplex: Full
        Port: MII
        PHYAD: 32
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: pumbg
        Wake-on: p
        Current message level: 0x00000007 (7)
        Link detected: yes

After this I tried testing network speed using iperf, and got speeds of ~ 67 Mbps. With e100, I used to get ~ 97 Mbps. Anyways this is an 3-4 year old NIC, plugged (and unused) into my desktop unused since 2-3 years. So will try testing speeds with a new NIC soon.