Re: [PATCH stable 4.9 v2] net: dsa: bcm_sf2: force pause link settings

[Vladimir Oltean <olteanv@gmail.com>]

Hi Florian,

On Wed, Jul 06, 2022 at 12:24:54PM -0700, Florian Fainelli wrote:
> From: Doug Berger <opendmb@gmail.com>
> 
> commit 7c97bc0128b2eecc703106112679a69d446d1a12 upstream
> 
> The pause settings reported by the PHY should also be applied to the
> GMII port status override otherwise the switch will not generate pause
> frames towards the link partner despite the advertisement saying
> otherwise.
> 
> Fixes: 246d7f773c13 ("net: dsa: add Broadcom SF2 switch driver")
> Signed-off-by: Doug Berger <opendmb@gmail.com>
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> Link: https://lore.kernel.org/r/20220623030204.1966851-1-f.fainelli@gmail.com
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> Changes in v2:
> 
> - use both local and remote advertisement to determine when to apply
>   flow control settings
> 
>  drivers/net/dsa/bcm_sf2.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/net/dsa/bcm_sf2.c b/drivers/net/dsa/bcm_sf2.c
> index 40b3adf7ad99..562b5eb23d90 100644
> --- a/drivers/net/dsa/bcm_sf2.c
> +++ b/drivers/net/dsa/bcm_sf2.c
> @@ -600,7 +600,9 @@ static void bcm_sf2_sw_adjust_link(struct dsa_switch *ds, int port,
>  	struct bcm_sf2_priv *priv = bcm_sf2_to_priv(ds);
>  	struct ethtool_eee *p = &priv->port_sts[port].eee;
>  	u32 id_mode_dis = 0, port_mode;
> +	u16 lcl_adv = 0, rmt_adv = 0;
>  	const char *str = NULL;
> +	u8 flowctrl = 0;
>  	u32 reg;
>  
>  	switch (phydev->interface) {
> @@ -667,10 +669,24 @@ static void bcm_sf2_sw_adjust_link(struct dsa_switch *ds, int port,
>  		break;
>  	}
>  
> +	if (phydev->pause)
> +		rmt_adv = LPA_PAUSE_CAP;
> +	if (phydev->asym_pause)
> +		rmt_adv |= LPA_PAUSE_ASYM;
> +	if (phydev->advertising & ADVERTISED_Pause)
> +		lcl_adv = ADVERTISE_PAUSE_CAP;
> +	if (phydev->advertising & ADVERTISED_Asym_Pause)
> +		lcl_adv |= ADVERTISE_PAUSE_ASYM;
> +	flowctrl = mii_resolve_flowctrl_fdx(lcl_adv, rmt_adv);

IEEE 802.3 says "The PAUSE function shall be enabled according to Table
28B–3 only if the highest common denominator is a full duplex technology."

> +
>  	if (phydev->link)
>  		reg |= LINK_STS;
>  	if (phydev->duplex == DUPLEX_FULL)
>  		reg |= DUPLX_MODE;
> +	if (flowctrl & FLOW_CTRL_TX)
> +		reg |= TXFLOW_CNTL;
> +	if (flowctrl & FLOW_CTRL_RX)
> +		reg |= RXFLOW_CNTL;
>  
>  	core_writel(priv, reg, CORE_STS_OVERRIDE_GMIIP_PORT(port));
>  
> -- 
> 2.25.1
>