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Feasibility of Ethernet connection in new project based on DM8148 and AM3505

Jemish Patel
Intellectual 740 points
Other Parts Discussed in Thread: AM3505

Hi All,

  • We are going to start new project based on DM8148 and AM3505.
  • In this project we want to use internal switch of DM8148.
  • In this case, the AM3505 will be connected directly via RMII interface to EMAC1 port of DM8148.
  • which should be configured to static 100Mb full duplex configuration
  • The direct implication is that the DM8148 must be turned on and enable the switch in order that AM3505 will have external Ethernet connection through the RJ-45 port.
  • In order to implement the above, DM8148 u-boot must enable the internal Ethernet switch.
  • Current official u-boot from TI supports only single EMAC0 port and the switch is enabled only from Kernel space.
  • For reference I have attached image "ethernect_connection.".
  • First of all I want to know that is it feasible to connect DM8148 ethernet switch with given connection shown in image?
  • If it is feasible then can we configure DM8148 3PSW switch from u-boot to enable EMCA0 and EMAC1 port?

Regards,

Jemish

  • 0
    Mastermind 8020 points

    Making the switch operational consists minimally of:

    • enable SATA PLL and ethernet clocks
    • configure pinmux and GMII_SEL
    • configure MACCONTROL for both ports
    • write 0xC0000000 to ALE_CONTROL to clear and enable the ALE
    • write 0x3 to ALE_PORTCTL1 and ALE_PORTCTL2 to set both ports to forwarding state

    I'm currently connected to the internet through a dm8148 whose switch was enabled in this way (and no OS running) so I know this procedure gets the switch operational.

    Of course it no doubt violates various standards since a well-behaved switch is supposed to do Spanning Tree and such before setting a port to forwarding state, but in your case where one port is occupied by a single fixed device there is little danger of a bridge loop so I don't think it will cause any issues.

    I can't comment on the hardware side of your question since I have no experience with cross-connecting ethernet directly between chips, my board simply has two PHYs connected via RGMII.

  • 0
    TI__Guru**** 170625 points

    Jemish,

    Jemish Patel said:
    If it is feasible then can we configure DM8148 3PSW switch from u-boot to enable EMCA0 and EMAC1 port?

    Have a look also in the below wiki page, might be in help:

    http://processors.wiki.ti.com/index.php/TI81xx_PSP_Porting_Guide#CPSW_EMAC_1_bringup_in_uboot

    Best Regards,
    Pavel