netdev - RE: [PATCH v3 4/5] net: hpe: Add GXP UMAC Driver

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Date: Thu, 17 Aug 2023 19:19:55 +0000
From: "Hawkins, Nick" <nick.hawkins@....com>
To: Andrew Lunn <andrew@...n.ch>
CC: "christophe.jaillet@...adoo.fr" <christophe.jaillet@...adoo.fr>,
        "simon.horman@...igine.com" <simon.horman@...igine.com>,
        "Verdun, Jean-Marie"
	<verdun@....com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org"
	<kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" <krzysztof.kozlowski+dt@...aro.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 4/5] net: hpe: Add GXP UMAC Driver

Hi Andrew,

> > +static int umac_init_hw(struct net_device *ndev)


> > +{
> > +	} else {
> > +		value |= UMAC_CFG_FULL_DUPLEX;
> > +
> > +		if (ndev->phydev->speed == SPEED_1000) {

> I'm pretty sure i pointed this out once before. It is not safe to
> access phydev members outside of the adjust link callback.

My mistake I missed this phydev member access. I will rely on
the adjust link callback to configure it.

> > +static int umac_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> > +{
> > +	struct umac_priv *umac = netdev_priv(ndev);
> > +	struct umac_tx_desc_entry *ptxdesc;
> > +	unsigned int length;
> > +	u8 *pframe;
> > +
> > +	ptxdesc = &umac->tx_descs->entrylist[umac->tx_cur];
> > +	pframe = umac->tx_descs->framelist[umac->tx_cur];
> > +
> > +	length = skb->len;
> > +	if (length > 1514) {
> > +		netdev_err(ndev, "send data %d bytes > 1514, clamp it to 1514\n",
> > +			   skb->len);

> Than should be rate limited.

How is this done? Is there a particular function to call that
will handle it in the backend?
I thought the rate limiting is happening in this
function already below at:

/* if current tx ring buffer is full, stop the queue */
        ptxdesc = &umac->tx_descs->entrylist[umac->tx_cur];
        if (ptxdesc->status & UMAC_RING_ENTRY_HW_OWN)
                netif_stop_queue(ndev);

> Also, if you chop the end of the packet, it is going to be useless. It
> is better to drop it, to improve your goodput.

I will drop it.

Thanks,

-Nick Hawkins