Configuring AM335x ethernet for RMII mode?

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1

Hi Guys,

I have a new custom board coming in soon, based on the BeagleBone. The hw guys tell me that the ethernet uses RMII. In looking at the U-Boot board specific code (arch/arm/cpu/armv7/am33xx/board.c, function board_eth_init) I see the Ethernet seems to be configured for either MII mode if it’s a BeagleBone else RGMII mode:

if (board_is_bone()) {
writel(MII_MODE_ENABLE, &cdev->miisel);
cpsw_slaves[0].phy_if = cpsw_slaves[1].phy_if =
PHY_INTERFACE_MODE_MII;
else {
writel(RGMII_MODE_ENABLE, &cdev->miisel);
cpsw_slaves[0].phy_if = cpsw_slaves[1].phy_if =
PHY_INTERFACE_MODE_RGMII;
}

The relevant constants are:

#define MII_MODE_ENABLE 0x0
#define RGMII_MODE_ENABLE 0xA

Does anyone know what value should be used to configure ethernet for RMII mode?

2

Depending on what PHY you use and the clocking mode you use, it may not matter. If the HW is not designed in a specific way, it may not work. You need an external clock to make RMII work.

I would start with the HW guys and make sure they have designed something that has a chance to work.

Gerald