linux-kernel - Re: [PATCH 2/2] net: dsa: microchip: Provide Module 4 KSZ9477 errata (DS80000754C)

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Message-ID: <9504d420-c137-2fde-312d-2c8e6f84ddd1@gmail.com>
Date:   Thu, 24 Aug 2023 08:54:37 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Lukasz Majewski <lukma@...x.de>,
        Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com
Cc:     Andrew Lunn <andrew@...n.ch>, Vladimir Oltean <olteanv@...il.com>,
        davem@...emloft.net, Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] net: dsa: microchip: Provide Module 4 KSZ9477 errata
 (DS80000754C)



On 8/24/2023 8:48 AM, Lukasz Majewski wrote:
> The KSZ9477 errata points out the link up/down problem when EEE is enabled
> in the device to which the KSZ9477 tries to auto negotiate.
> 
> The suggested workaround is to clear advertisement EEE registers
> (accessed as per port MMD one).
> 
> Signed-off-by: Lukasz Majewski <lukma@...x.de>
> ---
>   drivers/net/dsa/microchip/ksz9477.c | 40 ++++++++++++++++++++++++++++-
>   1 file changed, 39 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/microchip/ksz9477.c b/drivers/net/dsa/microchip/ksz9477.c
> index cb6aa7c668a8..563f497ba656 100644
> --- a/drivers/net/dsa/microchip/ksz9477.c
> +++ b/drivers/net/dsa/microchip/ksz9477.c
> @@ -1128,6 +1128,44 @@ int ksz9477_enable_stp_addr(struct ksz_device *dev)
>   	return 0;
>   }
>   
> +static int ksz9477_errata(struct dsa_switch *ds)
> +{
> +	struct ksz_device *dev = ds->priv;
> +	u16 val;
> +	int p;
> +
> +	/* KSZ9477 Errata DS80000754C
> +	 *
> +	 * Module 4: Energy Efficient Ethernet (EEE) feature select must be
> +	 * manually disabled
> +	 *   The EEE feature is enabled by default, but it is not fully
> +	 *   operational. It must be manually disabled through register
> +	 *   controls. If not disabled, the PHY ports can auto-negotiate
> +	 *   to enable EEE, and this feature can cause link drops when linked
> +	 *   to another device supporting EEE.
> +	 *
> +	 *   Only PHY ports (dsa user) [0-4] need to have the EEE advertisement
> +	 *   bits cleared.
> +	 */
> +
> +	for (p = 0; p < ds->num_ports; p++) {
> +		if (!dsa_is_user_port(ds, p))
> +			continue;
> +
> +		ksz9477_port_mmd_read(dev, p, MMD_DEVICE_ID_EEE_ADV,
> +				      MMD_EEE_ADV, &val, 1);
> +
> +		pr_err("%s: PORT: %d val: 0x%x pc: %d\n", __func__, p, val,
> +		       ds->num_ports);

Left over debugging?

> +
> +		val &= ~(EEE_ADV_100MBIT | EEE_ADV_1GBIT);
> +		ksz9477_port_mmd_write(dev, p, MMD_DEVICE_ID_EEE_ADV,
> +				       MMD_EEE_ADV, &val, 1);
> +	}
> +
> +	return 0;

You don't propagate any error, so make this return void?
-- 
Florian