Re: [PATCH RFC net-next v2 16/17] net: stmmac: Move internal PCS init method to stmmac_pcs.c

Russell King (Oracle)
2024-06-28T14:36:48Z

On Mon, Jun 24, 2024 at 04:26:33PM +0300, Serge Semin wrote:
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 72c2d3e2c121..743d356f6d12 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -950,13 +950,16 @@ static struct phylink_pcs *stmmac_mac_select_pcs(struct phylink_config *config,
> {
> struct stmmac_priv *priv = netdev_priv(to_net_dev(config->dev));
>
> + if (priv->hw->pcs)
> + return &priv->hw->mac_pcs;
> +
> if (priv->hw->xpcs)
> return &priv->hw->xpcs->pcs;
>
> if (priv->hw->phylink_pcs)
> return priv->hw->phylink_pcs;
>
> - return stmmac_mac_phylink_select_pcs(priv, interface);
> + return NULL;

I really really don't like this due to:

1. I spent a long time working out what the priority here should be, and
you've just thrown all that work away by changing it - to something that
I believe is incorrect.

2. I want to eventually see this function checking the interface type
before just handing out a random PCS, and it was my intention to
eventually that into the MACs own select_pcs() methods. Getting rid of
those methods means that the MACs themselves now can't make the
decision which is where that should be.

3. When operating in RGMII "inband" mode, the .pcs_config etc doesn't
make much sense (we're probably accessing registers that don't exist)
and I had plans to split this into a RGMII "PCS" which was just a PCS
that implemented .pcs_get_state(), a stub .pcs_config(), and a separate
fully-featured "SGMII PCS".

So, I would like to eventually see here something like:

if (priv->hw->xpcs)
return &priv->hw->xpcs->pcs;

if (priv->hw->phylink_pcs)
return priv->hw->phylink_pcs;

if (!(priv->plat->flags & STMMAC_FLAG_HAS_INTEGRATED_PCS)) {
if (phy_interface_mode_is_rgmii(priv->plat->mac_interface))
return &priv->hw->mac_rgmii_pcs;

if (priv->dma_cap.pcs &&
priv->plat->mac_interface == PHY_INTERFACE_MODE_SGMII)
return &priv->hw->mac_sgmii_pcs;
}

return NULL;

> +void dwmac_pcs_init(struct mac_device_info *hw)
> +{
> + struct stmmac_priv *priv = hw->priv;
> + int interface = priv->plat->mac_interface;
> +
> + if (priv->plat->flags & STMMAC_FLAG_HAS_INTEGRATED_PCS)
> + return;
> + else if (phy_interface_mode_is_rgmii(interface))
> + hw->pcs = STMMAC_PCS_RGMII;
> + else if (priv->dma_cap.pcs && interface == PHY_INTERFACE_MODE_SGMII)
> + hw->pcs = STMMAC_PCS_SGMII;
> +
> + hw->mac_pcs.neg_mode = true;
> +}

Please move "hw->mac_pcs.neg_mode = true;" to where the PCS method
functions are implemented - it determines whether the PCS method
functions take the AN mode or the neg mode, and this is a property of
their implementations. It should not be split away from them.

Thanks.

--
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