Subject: Re: [PATCH net v1] mlxbf_gige: disable port during stop()

From: Benjamin Poirier <[email-masked]>
Date: Mon, 19 Aug 2024 14:55:12 -0400

On 2024-08-16 16:48 -0400, David Thompson wrote:
> The mlxbf_gige_open() routine initializes and enables the
> Gigabit Ethernet port from a hardware point of view. The
> mlxbf_gige_stop() routine must disable the port hardware
> to fully quiesce it.
> 
> Fixes: f92e1869d74e ("Add Mellanox BlueField Gigabit Ethernet driver")
> Reviewed-by: Asmaa Mnebhi <[email-masked]>
> Signed-off-by: David Thompson <[email-masked]>
> ---
>  drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
> index 385a56ac7348..12942a50e1bb 100644
> --- a/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
> +++ b/drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c
> @@ -205,8 +205,14 @@ static int mlxbf_gige_open(struct net_device *netdev)
>  static int mlxbf_gige_stop(struct net_device *netdev)
>  {
>  	struct mlxbf_gige *priv = netdev_priv(netdev);
> +	u64 control;
> +
> +	control = readq(priv->base + MLXBF_GIGE_CONTROL);
> +	control &= ~MLXBF_GIGE_CONTROL_PORT_EN;
> +	writeq(control, priv->base + MLXBF_GIGE_CONTROL);
>  
>  	writeq(0, priv->base + MLXBF_GIGE_INT_EN);
> +	mb();

checkpatch says:
WARNING: memory barrier without comment
#37: FILE: drivers/net/ethernet/mellanox/mlxbf_gige/mlxbf_gige_main.c:215:
+       mb();

Is this memory barrier paired with another one?