[RFC PATCH 4/7] ath79: prepare for 1-port TP-Link EAP2x5 devices

[Sander Vanheule]

Hi David,

On Sat, 2020-07-18 at 21:45 +0200, David Bauer wrote:
> > +	gmac-config {
> > +		device = <&gmac>;
> > +
> > +		rgmii-ge0 = <1>;
> > +		ge0-sgmii = <1>;
> > +		rxdv-delay = <3>;
> > +		rxd-delay = <3>;
> 
> This does not make a lot of sense to me. Enabling both RGMII
> as well as SGMII for GE0 might work but it is most likely an
> undefined state.
> 
> Also the QCA956x does not offer RGMII for the MAC at all. Therefore,
> setting RGMII
> delays dhouldn't be necessary.
> 
> This applies to your GMAC settings  export in general. From my
> perspective, only the
> ge0-sgmii should matter at all?
> 

I guess j-d-r used TP-Link's code and went from there, since it works.
And I must admit that my knowledge on xMII and these SoCs is very
superficial, so none of this code is obvious to me.
If I only keep the ge0-sgmii as you suggested, things still work, so I
guess I can trim things down to keep just that.

For reference, TP-Link (Qualcomm?) sets things up as follows:
   void ath_gmac_mii_setup(void)
   {
   	unsigned int mgmt_cfg_val;
   	ath_reg_wr(SWITCH_CLOCK_SPARE_ADDRESS, 0xc5200);

   	mgmt_cfg_val = 7;
   	ath_reg_wr(ETH_CFG_ADDRESS, ETH_CFG_ETH_RXDV_DELAY_SET(3) |
   				ETH_CFG_ETH_RXD_DELAY_SET(3)|
   				ETH_CFG_RGMII_GE0_SET(1) |
   				ETH_CFG_GE0_SGMII_SET(1) );
   	ath_reg_wr(ETH_XMII_ADDRESS, ETH_XMII_TX_INVERT_SET(1) |
               			     ETH_XMII_RX_DELAY_SET(2)  |
               			     ETH_XMII_TX_DELAY_SET(1)  |
   				     ETH_XMII_GIGE_SET(1));
   	udelay(1000);
   	ath_reg_wr(ATH_MAC_MII_MGMT_CFG, mgmt_cfg_val | (1 << 31));
   	ath_reg_wr(ATH_MAC_MII_MGMT_CFG, mgmt_cfg_val);
   }

§8.8.1 ETH_CFG in the datasheet I referred to earlier lists the rgmii-
ge0/rgmii-enabled bit as reserved, but the delays are listed there.


Thanks,
Sander