Re: [RFC PATCH net-next 4/5] net: macb: Configure High Speed Mac for given speed.

[Karumanchi, Vineeth]

Hi Maxime,

On 10/9/2024 12:06 PM, Maxime Chevallier wrote:
> Hello,
>
> On Wed, 9 Oct 2024 11:09:45 +0530
> Vineeth Karumanchi <vineeth.karumanchi@xxxxxxx> wrote:
>
> > HS Mac configuration steps:
> > - Configure speed and serdes rate bits of USX_CONTROL register from
> >    user specified speed in the device-tree.
> > - Enable HS Mac for 5G and 10G speeds.
> > - Reset RX receive path to achieve USX block lock for the
> >    configured serdes rate.
> > - Wait for USX block lock synchronization.
> >
> > Move the initialization instances to macb_usx_pcs_link_up().
> >
> > Signed-off-by: Vineeth Karumanchi <vineeth.karumanchi@xxxxxxx>
> [...]
>
> >   
> >   /* DMA buffer descriptor might be different size
> >    * depends on hardware configuration:
> > @@ -564,14 +565,59 @@ static void macb_usx_pcs_link_up(struct phylink_pcs *pcs, unsigned int neg_mode,
> >   				 int duplex)
> >   {
> >   	struct macb *bp = container_of(pcs, struct macb, phylink_usx_pcs);
> > -	u32 config;
> > +	u32 speed_val, serdes_rate, config;
> > +	bool hs_mac = false;
> > +
> > +	switch (speed) {
> > +	case SPEED_1000:
> > +		speed_val = HS_SPEED_1000M;
> > +		serdes_rate = MACB_SERDES_RATE_1G;
> > +		break;
> > +	case SPEED_2500:
> > +		speed_val = HS_SPEED_2500M;
> > +		serdes_rate = MACB_SERDES_RATE_2_5G;
> > +		break;
> > +	case SPEED_5000:
> > +		speed_val = HS_SPEED_5000M;
> > +		serdes_rate = MACB_SERDES_RATE_5G;
> > +		hs_mac = true;
> > +		break;
> You support some new speeds and modes, so you also need to update :
>
>   - The macb_select_pcs() code, as right now it will return NULL for any
> mode that isn't 10GBaseR or SGMII, so for 2500/5000 speeds, that
> probably won't work. And for 1000, the default PCS will be used and not
> USX
>
>   - the phylink mac_capabilities, so far 2500 and 5000 speeds aren't
> reported as supported.
>
>   - the phylink supported_interfaces, I suppose the IP uses 2500BaseX
> and 5GBaseT ? or maybe some usxgmii flavors ?

with 10GBaseR, ethtool is showing multiple speed support. ( 1G, 2.5G, 5G 
and 10G )
The only check I see with 10GbaseR is max speed shouldn't be greater 
than 10G, which
suits the IP requirement.

> > +	case SPEED_10000:
> > +		speed_val = HS_SPEED_10000M;
> > +		serdes_rate = MACB_SERDES_RATE_10G;
> > +		hs_mac = true;
> > +		break;
> > +	default:
> > +		netdev_err(bp->dev, "Specified speed not supported\n");
> > +		return;
> > +	}
> > +
> > +	/* Enable HS MAC for high speeds */
> > +	if (hs_mac) {
> > +		config = macb_or_gem_readl(bp, NCR);
> > +		config |= GEM_BIT(ENABLE_HS_MAC);
> > +		macb_or_gem_writel(bp, NCR, config);
> > +	}
> It looks like you moved the MAC selection between HS MAC and non-HS MAC
> from the phylink .mac_config to PCS config.
>
> This configuration is indeed a MAC-side configuration from what I
> understand, you shouldn't need to set that in PCS code. Maybe instead,
> check the interface mode in macb_mac_config, and look if you're in
> 5GBaseR / 10GBaseR to select the MAC ?

Yes, agreed!

As our current HW setup doesn't have AN and PHY, to support speed change 
using ethtool
I have moved the above MAC config into PCS. I will explore on setting 
MAC config based on speed
instead of interface in  macb_mac_config().

Please let me know your thoughts and comments.

--
🙏 vineeth

[...]