Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH NET 3/3] net: hns: add configuration constraints for 1000M
 half
To:     Andrew Lunn <andrew@lunn.ch>
CC:     <davem@davemloft.net>, <netdev@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linuxarm@huawei.com>,
        <yisen.zhuang@huawei.com>, <salil.mehta@huawei.com>
References: <1535082143-122281-1-git-send-email-lipeng321@huawei.com>
 <1535082143-122281-4-git-send-email-lipeng321@huawei.com>
 <20180824034119.GA29111@lunn.ch>
 <194ac663-94d8-55e2-0231-a6be53e35f04@huawei.com>
 <20180824132857.GA1999@lunn.ch>
From:   "lipeng (Y)" <lipeng321@huawei.com>
Message-ID: <7c40c758-2ef2-665d-f429-0cc4e63a7a38@huawei.com>
Date:   Sat, 25 Aug 2018 09:21:55 +0800
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.5.2
MIME-Version: 1.0
In-Reply-To: <20180824132857.GA1999@lunn.ch>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 2018/8/24 21:28, Andrew Lunn wrote:
> On Fri, Aug 24, 2018 at 02:39:36PM +0800, lipeng (Y) wrote:
>>
>> On 2018/8/24 11:41, Andrew Lunn wrote:
>>> On Fri, Aug 24, 2018 at 11:42:23AM +0800, Peng Li wrote:
>>>> Hisilicon hip05 and hip06 board network card do not support
>>>> 1000M half configuration. Driver can not config gmac as
>>>> 1000M half.
>>>>
>>>> Signed-off-by: Peng Li <lipeng321@huawei.com>
>>> Hi Peng
>>>
>>> Does the driver remove SUPPORTED_1000baseT_Half from
>>> phydev->supported?  If you do that, the PHY should never negotiate
>>> this speed.
>>>
>>>     Andrew
>> Hi, Andrew,
>>
>> The driver has removed SUPPORTED_1000baseT_Half from
>>
>> phydev->supported.
>>
>> the code is :
>> #define MAC_GMAC_SUPPORTED \
>> 	(SUPPORTED_10baseT_Half \
>> 	| SUPPORTED_10baseT_Full \
>> 	| SUPPORTED_100baseT_Half \
>> 	| SUPPORTED_100baseT_Full \
>> 	| SUPPORTED_Autoneg)
>>   h->if_support = MAC_GMAC_SUPPORTED;
>>   h->if_support |= SUPPORTED_1000baseT_Full;
>> phydev->supported &= h->if_support;
>>
>> As gmac do not support 1000M half, we add this patch to
>> make sure that no users can set 1000M half in any case.
> Well, not quite. What this patch does is protect the hardware when it
> is asked to change to an unsupported mode. This patch has nothing to
> do with user APIs.
>
> The user API for setting link modes is hns_nic_set_link_ksettings().
>
> What you do have is
>
>                  if (speed == SPEED_1000 && cmd->base.duplex == DUPLEX_HALF)
>                          return -EINVAL;
>
> which should stop somebody setting up a fixed speed link at 1000Half.
>
> But you don't do anything with cmd->link_modes.advertising. However,
> when you call phy_ethtool_ksettings_set(), it gets AND'ed with
> phydev->supported, which you have already removed 1000Half from.
>
> So is this a patch for a theoretical problem? Or have you seen it
> happen? If it did happen, how did the user configure it to cause this
> problem? That user API needs to prevent it.
>
> 	 Andrew
Hi,  Andrew,

HW  do not support 1000M half, and the driver has done the 2 things:
1, remove SUPPORTED_1000baseT_Half from phydev->supported.
2,   add the protect in  hns_nic_set_link_ksettings().

This patch is a  theoretical protect, and the problem does not really  
happen.

I think you really get the point, do you think we need this patch?

Thanks
> .
>