linux-kernel - Re: [PATCH v3 12/13] net: phy: adjust qca8081 master/slave seed value if link down

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Date:   Tue, 19 Oct 2021 00:04:06 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Luo Jie <luoj@...eaurora.org>
Cc:     hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, sricharan@...eaurora.org
Subject: Re: [PATCH v3 12/13] net: phy: adjust qca8081 master/slave seed
 value if link down

On Mon, Oct 18, 2021 at 11:33:32AM +0800, Luo Jie wrote:
> 1. The master/slave seed needs to be updated when the link can't
> be created.
> 
> 2. The case where two qca8081 PHYs are connected each other and
> master/slave seed is generated as the same value also needs
> to be considered, so adding this code change into read_status
> instead of link_change_notify.
> 
> Signed-off-by: Luo Jie <luoj@...eaurora.org>
> ---
>  drivers/net/phy/at803x.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/net/phy/at803x.c b/drivers/net/phy/at803x.c
> index 5d007f89e9d3..77aaf9e72781 100644
> --- a/drivers/net/phy/at803x.c
> +++ b/drivers/net/phy/at803x.c
> @@ -1556,6 +1556,22 @@ static int qca808x_read_status(struct phy_device *phydev)
>  	else
>  		phydev->interface = PHY_INTERFACE_MODE_SMII;
>  
> +	/* generate seed as a lower random value to make PHY linked as SLAVE easily,
> +	 * except for master/slave configuration fault detected.
> +	 * the reason for not putting this code into the function link_change_notify is
> +	 * the corner case where the link partner is also the qca8081 PHY and the seed
> +	 * value is configured as the same value, the link can't be up and no link change
> +	 * occurs.
> +	 */
> +	if (!phydev->link) {
> +		if (phydev->master_slave_state == MASTER_SLAVE_STATE_ERR) {
> +			qca808x_phy_ms_seed_enable(phydev, false);
> +		} else {
> +			qca808x_phy_ms_random_seed_set(phydev);
> +			qca808x_phy_ms_seed_enable(phydev, true);
> +		}
> +	}

Are you assuming here that the status is polled once a second, and
each poll you choose a new seed and see if it succeeds? What happens
when interrupts are used, not polling?

     Andrew