netdev - Re: [PATCH v1 1/1] net: phy: micrel: Add workaround for incomplete autonegotiation

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Date: Wed, 27 Dec 2023 23:19:40 +0100
From: Marek Mojík <marek.mojik@....cz>
To: Asmaa Mnebhi <asmaa@...dia.com>, davem@...emloft.net,
 linux@...linux.org.uk, netdev@...r.kernel.org
Cc: davthompson@...dia.com
Subject: Re: [PATCH v1 1/1] net: phy: micrel: Add workaround for incomplete
 autonegotiation



On 12/26/23 15:19, Asmaa Mnebhi wrote:
> Very rarely, the KSZ9031 fails to complete autonegotiation although it was
> initiated via phy_start(). As a result, the link stays down. Restarting
> autonegotiation when in this state solves the issue.
> 
> Signed-off-by: Asmaa Mnebhi <asmaa@...dia.com>
> ---
>   drivers/net/phy/micrel.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
> index 08e3915001c3..de8140c5907f 100644
> --- a/drivers/net/phy/micrel.c
> +++ b/drivers/net/phy/micrel.c
> @@ -1475,6 +1475,7 @@ static int ksz9031_get_features(struct phy_device *phydev)
>   
>   static int ksz9031_read_status(struct phy_device *phydev)
>   {
> +	u8 timeout = 10;
>   	int err;
>   	int regval;
>   
> @@ -1494,6 +1495,22 @@ static int ksz9031_read_status(struct phy_device *phydev)
>   		return genphy_config_aneg(phydev);
>   	}
>   
> +	/* KSZ9031's autonegotiation takes normally 4-5 seconds to complete.
> +	 * Occasionally it fails to complete autonegotiation. The workaround is
> +	 * to restart it.
> +	 */
> +        if (phydev->autoneg == AUTONEG_ENABLE) {
> +		while (timeout) {
> +			if (phy_aneg_done(phydev))
> +				break;
> +			mdelay(1000);
> +			timeout--;
> +		};
> +
> +		if (timeout == 0)
> +			phy_restart_aneg(phydev);
> +	}
> +
>   	return 0;
>   }


Hi Asmaa, mdelay is busy-wait, so you're unnecessarily blocking cpu core
for 10 seconds, msleep should be used here as explained in the docs 
https://kernel.org/doc/Documentation/timers/timers-howto.txt

Marek