[ewg] strange value of IB port rate

[Mahesh Chaudhari]

Hi All,
i have Mellanox dual port IB card installed in m/c
when i do :

             "cat /sys/class/infiniband/mthca0/ports/1/rate "
it shows 20 Gb/sec (4X DDR)

while on port2 

                " cat /sys/class/infiniband/mthca0/ports/2/rate "
it shows 8.5 Gb/sec (4X)

when i looked at source code, i found a equation to calculate rate :

                       rate = 25 * ib_width_enum_to_int(attr.active_width) * attr.active_speed;
                       

                       return sprintf(buf, "%d%s Gb/sec (%dX%s)\n",
                       rate / 10, rate % 10 ? ".5" : "",
                       ib_width_enum_to_int(attr.active_width), speed);



                                where   ib_width_enum_to_int(attr.active_width) =  1 | 4 |8 |12 | -1(error)
                                             attr.active_speed = 1 | 2 | 4 


    i am wondering, how could it possible to get such an odd value (8.5 Gbps) 


/usr/ofed/sbin/ibstatus utility also shows :


Infiniband device 'mthca0' port 1 status:
    default gid:     fe80:0000:0000:0000:001a:4bff:ff0c:96e5
    base lid:     0x6
    sm lid:         0x1
    state:         4: ACTIVE
    phys state:     5: LinkUp
    rate:         20 Gb/sec (4X DDR)
    link_layer:     InfiniBand

Infiniband device 'mthca0' port 2 status:
    default gid:     fe80:0000:0000:0000:001a:4bff:ff0c:96e6
    base lid:     0x0
    sm lid:         0x0
    state:         1: DOWN
    phys state:     2: Polling
    rate:         8.5 Gb/sec (4X)
    link_layer:     InfiniBand





Any Clue ???
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