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SubjectRE: [PATCH net-next] net: hns3: Add support to change MTU in hardware & netdev
Date
Hi Andrew

> -----Original Message-----
> From: Andrew Lunn [mailto:andrew@lunn.ch]
> Sent: Friday, August 18, 2017 5:02 PM
> To: Salil Mehta
> Cc: davem@davemloft.net; Zhuangyuzeng (Yisen); lipeng (Y);
> mehta.salil.lnk@gmail.com; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; linux-rdma@vger.kernel.org; Linuxarm
> Subject: Re: [PATCH net-next] net: hns3: Add support to change MTU in
> hardware & netdev
>
> > for example,
> > file: drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c
> > static int init_one(struct pci_dev *pdev, const struct pci_device_id
> *ent)
> >
> > netdev->priv_flags |= IFF_UNICAST_FLT;
> >
> > + /* MTU range: 81 - 9600 */
> > + netdev->min_mtu = 81;
> > + netdev->max_mtu = MAX_MTU;
>
> In this cause, the driver is not using the default values. So it sets
> them.
>
> Anyway, try it. After your alloc_etherdev_mqs(), print the value of
> min_mtu. It should already be set to MIN_ETH_MTU.
I understand your point. In this case, I would like to keep the
range being set by the driver just to be more explicit.
So for now keep this initialization in the driver?

Thanks
Salil
>
> > I see. IMHO HNS3 is currently limited by maximum buffer per
> descriptor
> > which is 64k. I am sure such frames would get dropped in the hardware
> > itself and which I guess should be more preferable than dropping in
> > driver since it saves you some precious cpu cycles?
>
> If you hardware handles this, then you don't need to do anything.
Fine. Thanks!

Salil
>
> Andrew

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