linux-kernel - Re: [PATCH 08/12] staging: dpaa2-ethsw: handle Rx path on control interface

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Message-ID: <20191105143130.GD7189@lunn.ch>
Date:   Tue, 5 Nov 2019 15:31:30 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Ioana Ciornei <ioana.ciornei@....com>
Cc:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        f.fainelli@...il.com
Subject: Re: [PATCH 08/12] staging: dpaa2-ethsw: handle Rx path on control
 interface

> +static void ethsw_rx(struct ethsw_fq *fq,
> +		     const struct dpaa2_fd *fd)
> +{
> +	struct ethsw_core *ethsw = fq->ethsw;
> +	struct ethsw_port_priv *port_priv;
> +	struct net_device *netdev;
> +	struct vlan_ethhdr *hdr;
> +	struct sk_buff *skb;
> +	u16 vlan_tci, vid;
> +	int if_id = -1;
> +	int err;
> +
> +	/* prefetch the frame descriptor */
> +	prefetch(fd);
> +
> +	/* get switch ingress interface ID */
> +	if_id = upper_32_bits(dpaa2_fd_get_flc(fd)) & 0x0000FFFF;

Does the prefetch do any good, since the very next thing you do is
access the frame descriptor? Ideally you want to issue the prefetch,
do something else for a while, and then make use of what the prefetch
got.


> +
> +	if (if_id < 0 || if_id >= ethsw->sw_attr.num_ifs) {

Is if_id signed? Seems odd.

   Andrew