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

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Message-ID: <20230727065820.GZ11388@unreal>
Date:   Thu, 27 Jul 2023 09:58:20 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Junxian Huang <huangjunxian6@...ilicon.com>
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 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