Re: [PATCH net v1 2/2] net: phy: microchip: lan87xx: do not report SQI if no link

[Andrew Lunn]

On Wed, Jul 03, 2024 at 03:28:01PM +0200, Oleksij Rempel wrote:
> Do not report SQI if no link is detected. Otherwise ethtool will show
> non zero value even if no cable is attached.
> 
> Fixes: b649695248b15 ("net: phy: LAN87xx: add ethtool SQI support")
> Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> ---
>  drivers/net/phy/microchip_t1.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/phy/microchip_t1.c b/drivers/net/phy/microchip_t1.c
> index a35528497a576..22530a5b76365 100644
> --- a/drivers/net/phy/microchip_t1.c
> +++ b/drivers/net/phy/microchip_t1.c
> @@ -840,6 +840,9 @@ static int lan87xx_get_sqi(struct phy_device *phydev)
>  	u8 sqi_value = 0;
>  	int rc;
>  
> +	if (!phydev->link)
> +		return 0;
> +

Is this the correct place to fix this? Can any PHY report an SQI value
if there is no link? Maybe an automotive PHY using T1 and good old
fashioned CSMA/CD could report about background noise? But do they?

Maybe this should be fixed in linkstate_get_sqi()?

Also, maybe it should return -ENETDOWN, not 0. Do we want to say
"worse than class A SQI (unstable link)" when in fact the link is
"class G SQI (very good link)" once it is up?

	Andrew