Re: [PATCH net-next v2 5/5] net: phylink: provide fixed state for 1000base-X and 2500base-X

[Vladimir Oltean <olteanv@gmail.com>]

On Mon, Jan 13, 2025 at 09:22:44AM +0000, Russell King (Oracle) wrote:
> When decoding clause 22 state, if in-band is disabled and using either
> 1000base-X or 2500base-X, rather than reporting link-down, we know the
> speed, and we only support full duplex. Pause modes taken from XPCS.
> 
> This fixes a problem reported by Eric Woudstra.
> 
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> ---
>  drivers/net/phy/phylink.c | 29 +++++++++++++++++++----------
>  1 file changed, 19 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> index b79f975bc164..ff0efb52189f 100644
> --- a/drivers/net/phy/phylink.c
> +++ b/drivers/net/phy/phylink.c
> @@ -3882,27 +3882,36 @@ void phylink_mii_c22_pcs_decode_state(struct phylink_link_state *state,
>  	if (!state->link)
>  		return;
>  
> -	/* If in-band is disabled, then the advertisement data is not
> -	 * meaningful.
> -	 */
> -	if (neg_mode != PHYLINK_PCS_NEG_INBAND_ENABLED)
> -		return;
> -
>  	switch (state->interface) {
>  	case PHY_INTERFACE_MODE_1000BASEX:
> -		phylink_decode_c37_word(state, lpa, SPEED_1000);
> +		if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED) {
> +			phylink_decode_c37_word(state, lpa, SPEED_1000);
> +		} else {
> +			state->speed = SPEED_1000;
> +			state->duplex = DUPLEX_FULL;
> +			state->pause |= MLO_PAUSE_TX | MLO_PAUSE_RX;
> +		}
>  		break;
>  
>  	case PHY_INTERFACE_MODE_2500BASEX:
> -		phylink_decode_c37_word(state, lpa, SPEED_2500);
> +		if (neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED) {
> +			phylink_decode_c37_word(state, lpa, SPEED_2500);
> +		} else {
> +			state->speed = SPEED_2500;
> +			state->duplex = DUPLEX_FULL;
> +			state->pause |= MLO_PAUSE_TX | MLO_PAUSE_RX;
> +		}
>  		break;

Are the "else" branches necessary, given the "else" branch from
phylink_mac_pcs_get_state?

static void phylink_mac_pcs_get_state(struct phylink *pl,
				      struct phylink_link_state *state)
{
	struct phylink_pcs *pcs;
	bool autoneg;

	linkmode_copy(state->advertising, pl->link_config.advertising);
	linkmode_zero(state->lp_advertising);
	state->interface = pl->link_config.interface;
	state->rate_matching = pl->link_config.rate_matching;
	state->an_complete = 0;
	state->link = 1;

	pcs = pl->pcs;
	if (!pcs || pcs->neg_mode)
		autoneg = pl->pcs_neg_mode == PHYLINK_PCS_NEG_INBAND_ENABLED;
	else
		autoneg = linkmode_test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
					    state->advertising);

	if (autoneg) {
		state->speed = SPEED_UNKNOWN;
		state->duplex = DUPLEX_UNKNOWN;
		state->pause = MLO_PAUSE_NONE;
	} else {						|
		state->speed =  pl->link_config.speed;		|
		state->duplex = pl->link_config.duplex;		| this
		state->pause = pl->link_config.pause;		|
	}							|

	if (pcs)
		pcs->ops->pcs_get_state(pcs, pl->pcs_neg_mode, state);
	else
		state->link = 0;
}