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Re: [PATCH net-next] net: hns3: Add support to change MTU in hardware & netdev

From Andrew Lunn <andrew@lunn.ch>
Newsgroups linux.kernel
Subject Re: [PATCH net-next] net: hns3: Add support to change MTU in hardware & netdev
Date 2017-08-18 18:10 +0200
Message-ID <ufS0r-63B-29@gated-at.bofh.it> (permalink)
References <ufNN8-346-23@gated-at.bofh.it> <ufPFj-4ln-89@gated-at.bofh.it> <ufQUG-58U-17@gated-at.bofh.it> <ufR4n-5rS-51@gated-at.bofh.it> <ufRxp-5DE-49@gated-at.bofh.it>
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> 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 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.

   Andrew

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[PATCH net-next] net: hns3: Add support to change MTU in hardware & netdev Salil Mehta <salil.mehta@huawei.com> - 2017-08-18 13:40 +0200
  Re: [PATCH net-next] net: hns3: Add support to change MTU in  hardware & netdev Andrew Lunn <andrew@lunn.ch> - 2017-08-18 15:40 +0200
    RE: [PATCH net-next] net: hns3: Add support to change MTU in  hardware & netdev Salil Mehta <salil.mehta@huawei.com> - 2017-08-18 17:00 +0200
      Re: [PATCH net-next] net: hns3: Add support to change MTU in  hardware & netdev Andrew Lunn <andrew@lunn.ch> - 2017-08-18 17:10 +0200
        RE: [PATCH net-next] net: hns3: Add support to change MTU in  hardware & netdev Salil Mehta <salil.mehta@huawei.com> - 2017-08-18 17:40 +0200
          Re: [PATCH net-next] net: hns3: Add support to change MTU in  hardware & netdev Andrew Lunn <andrew@lunn.ch> - 2017-08-18 18:10 +0200
            RE: [PATCH net-next] net: hns3: Add support to change MTU in  hardware & netdev Salil Mehta <salil.mehta@huawei.com> - 2017-08-18 18:20 +0200
            RE: [PATCH net-next] net: hns3: Add support to change MTU in  hardware & netdev Salil Mehta <salil.mehta@huawei.com> - 2017-08-18 19:10 +0200

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