Re: [PATCH net-next 2/3] net: stmmac: xgmac: Correct supported speed modes

[G Thomas, Rohan]

Hi Russell,

Thanks for reviewing the patch.

On 7/17/2025 12:15 PM, Russell King (Oracle) wrote:
> On Mon, Jul 14, 2025 at 03:59:18PM +0800, Rohan G Thomas via B4 Relay wrote:
> > @@ -1532,8 +1542,8 @@ int dwxgmac2_setup(struct stmmac_priv *priv)
> >   		mac->mcast_bits_log2 = ilog2(mac->multicast_filter_bins);
> >   
> >   	mac->link.caps = MAC_ASYM_PAUSE | MAC_SYM_PAUSE |
> > -			 MAC_1000FD | MAC_2500FD | MAC_5000FD |
> > -			 MAC_10000FD;
> > +			 MAC_10FD | MAC_100FD | MAC_1000FD |
> > +			 MAC_2500FD | MAC_5000FD | MAC_10000FD;
> ...
> > @@ -405,6 +405,7 @@ static int dwxgmac2_get_hw_feature(void __iomem *ioaddr,
> >   	dma_cap->sma_mdio = (hw_cap & XGMAC_HWFEAT_SMASEL) >> 5;
> >   	dma_cap->vlhash = (hw_cap & XGMAC_HWFEAT_VLHASH) >> 4;
> >   	dma_cap->half_duplex = (hw_cap & XGMAC_HWFEAT_HDSEL) >> 3;
> > +	dma_cap->mbps_10_100 = (hw_cap & XGMAC_HWFEAT_GMIISEL) >> 1;
>
> What if dma_cap->mbps_10_100 is false? Should MAC_10FD | MAC_100FD
> still be set? What if dma_cap->half_duplex is set but
> dma_cap->mbps_10_100 is not? Should we avoid setting 10HD and 100HD?

As per the XGMAC databook, 10Mbps/100Mbps/1Gbps speeds are supported
only when the GMIISEL bit is set. As Serge pointed out, I also need to
consider the MAC version (≥ v3.00a) when enabling these modes. I’ll
update the next version of the patch to include checks for both the
GMIISEL bit and the MAC version before enabling the 
MAC_10FD/MAC_100FD/MAC_1000FD capabilities.

Also, regarding the HDSEL bit — it is set only if 10Mbps/100Mbps modes
are supported. I’ll include this condition as well when handling half
duplex support in the updated patch.

>

Best Regards,
Rohan