linux-kernel - Re: [PATCH v4 for-next] RDMA/core: Get IB width and speed from netdev

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Date:   Thu, 27 Jul 2023 15:53:54 +0800
From:   Junxian Huang <huangjunxian6@...ilicon.com>
To:     Leon Romanovsky <leon@...nel.org>
CC:     <jgg@...dia.com>, <linux-rdma@...r.kernel.org>,
        <linuxarm@...wei.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 for-next] RDMA/core: Get IB width and speed from netdev



On 2023/7/27 14:58, Leon Romanovsky wrote:
> On Thu, Jul 27, 2023 at 11:44:50AM +0800, Junxian Huang wrote:
>>
>>
>> On 2023/7/24 19:19, Leon Romanovsky wrote:
>>> On Fri, Jul 21, 2023 at 05:20:52PM +0800, Junxian Huang wrote:
>>>> From: Haoyue Xu <xuhaoyue1@...ilicon.com>
>>>>
>>>> Previously, there was no way to query the number of lanes for a network
>>>> card, so the same netdev_speed would result in a fixed pair of width and
>>>> speed. As network card specifications become more diverse, such fixed
>>>> mode is no longer suitable, so a method is needed to obtain the correct
>>>> width and speed based on the number of lanes.
>>>>
>>>> This patch retrieves netdev lanes and speed from net_device and
>>>> translates them to IB width and speed.
>>>>
>>>> Signed-off-by: Haoyue Xu <xuhaoyue1@...ilicon.com>
>>>> Signed-off-by: Luoyouming <luoyouming@...wei.com>
>>>> Signed-off-by: Junxian Huang <huangjunxian6@...ilicon.com>
>>>> ---
>>>>  drivers/infiniband/core/verbs.c | 100 +++++++++++++++++++++++++-------
>>>>  1 file changed, 79 insertions(+), 21 deletions(-)
>>>>
>>>> diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
>>>> index b99b3cc283b6..25367bd6dd97 100644
>>>> --- a/drivers/infiniband/core/verbs.c
>>>> +++ b/drivers/infiniband/core/verbs.c
>>>> @@ -1880,6 +1880,80 @@ int ib_modify_qp_with_udata(struct ib_qp *ib_qp, struct ib_qp_attr *attr,
>>>>  }
>>>>  EXPORT_SYMBOL(ib_modify_qp_with_udata);
>>>>  
>>>> +static void ib_get_width_and_speed(u32 netdev_speed, u32 lanes,
>>>> +				   u16 *speed, u8 *width)
>>>
>>> <...>
>>>
>>>> +	switch (netdev_speed / lanes) {
>>>> +	case SPEED_2500:
>>>> +		*speed = IB_SPEED_SDR;
>>>> +		break;
>>>> +	case SPEED_5000:
>>>> +		*speed = IB_SPEED_DDR;
>>>> +		break;
>>>> +	case SPEED_10000:
>>>> +		*speed = IB_SPEED_FDR10;
>>>> +		break;
>>>> +	case SPEED_14000:
>>>> +		*speed = IB_SPEED_FDR;
>>>> +		break;
>>>> +	case SPEED_25000:
>>>> +		*speed = IB_SPEED_EDR;
>>>> +		break;
>>>> +	case SPEED_50000:
>>>> +		*speed = IB_SPEED_HDR;
>>>> +		break;
>>>> +	case SPEED_100000:
>>>> +		*speed = IB_SPEED_NDR;
>>>> +		break;
>>>> +	default:
>>>> +		*speed = IB_SPEED_SDR;
>>>> +	}
>>>
>>> How did you come to these translation values?
>>>
>>> Thanks
>>
>> The IB spec defines the mapping relationship between IB speed and transfer
>> rate. For example, if the transfer rate of is 2.5Gbps(SPEED_2500), the IB
>> speed will be set to IB_SPEED_SDR.
> 
> Are you referring to "Table 250 - Enumeration of the Rate"?
> 
> Thanks
> 
>>
>> Junxian

Yes.

Junxian