Ok, I've solve my problem by myself. For any body interested in VLAN Trunk (Tagged) with WNR3500L and DD-WRT v24-sp2 (04/23/10) mini - build 14311.

I've configured vlan as usual with the Tagged Box checked and my vlan (9 for my test). After, I configured the Network setting with an IP for this vlan (Unbridged). I've also completly remove the iptables rules with iptables -F in the firewall command script (For testing purpose only). After all the setting, *** The MOST IMPORTANT Thing *** I've run those commands in ssh session :
nvram set vlan9ports="1t 8*"
nvram commit
This command set the vlan9 trunk on the physical port 4 (Phy port are in the wrong order) on the router. Note that you need the port 8* in your setting because this set the trunk between the internal ethernet port and the switch. After that everything work well. I've did some basic test but I try bridged communication within the same vlan on 2 different trunk port at near 500 Mbps (close to performance without trunk and stock firmware) with iperf. With routing between two different vlan, I've got a performance of about 150 Mbps (I did this test with 2 computer in different switch port.). I did'nt do any wireless test for the moment.

I am currious to see if it's the same thing with a Linksys WRT610n. I have one but it's still with the stock firmware. Maybe I will test it later.