Re: 5 GHz band support for Intel WiFi chips?

[Jarle Greipsland <jarle%uninett.no@localhost>]

Anders Magnusson <ragge%ludd.ltu.se@localhost> writes:
>> my impression from various web sites is that the Intel WiFi
>> device in my Lenovo T400s laptop has support for the 5 GHz band
>> channels.  However, it seems to never associate with any access
>> points using such channels.  It always ends up using some of the
>> 2.4 GHz channels instead, or not being able to associate with any
>> access point at all.
>>
> Just FYI: There are versions of the T400 that do not have 5GHz.
> You need to check the exact chip ID.

According to the NetBSD pcidevs file
  iwn0 at pci2 dev 0 function 0: vendor 0x8086 product 0x4236 (rev. 0x00)
translates to
  product INTEL WIFI_LINK_5300_2  0x4236  WiFi Link 5300
and the product brief[*] on Intel's web pages states that this is
part of a series that supports the dual bands 2.4 GHz / 5 GHz.
Is there an even more detailed chip ID I should look for?

Also, ifconfig -m iwn0 lists a number of 'mode 11a' media types.

I did also compile a kernel with IWN_DEBUG defined and set the
iwn_debug variable to 2 and got the following output:
iwn0 at pci2 dev 0 function 0: vendor 0x8086 product 0x4236 (rev. 0x00)
iwn0: interrupting at ioapic0 pin 17
EEPROM found
SKU capabilities=0x00f0
radio config=0x7708
adding chan 1 flags=0x6f maxpwr=15
adding chan 2 flags=0x6f maxpwr=15
adding chan 3 flags=0x6f maxpwr=15
adding chan 4 flags=0x6f maxpwr=15
adding chan 5 flags=0x6f maxpwr=15
adding chan 6 flags=0x6f maxpwr=15
adding chan 7 flags=0x6f maxpwr=15
adding chan 8 flags=0x6f maxpwr=15
adding chan 9 flags=0x6f maxpwr=15
adding chan 10 flags=0x6f maxpwr=15
adding chan 11 flags=0x6f maxpwr=15
adding chan 12 flags=0x61 maxpwr=15
adding chan 13 flags=0x61 maxpwr=15
adding chan 36 flags=0xe1 maxpwr=15
adding chan 40 flags=0xe1 maxpwr=15
adding chan 44 flags=0xe1 maxpwr=15
adding chan 48 flags=0xe1 maxpwr=15
adding chan 52 flags=0x31 maxpwr=15
adding chan 56 flags=0x31 maxpwr=15
adding chan 60 flags=0x31 maxpwr=15
adding chan 64 flags=0x31 maxpwr=15
adding chan 100 flags=0x31 maxpwr=15
adding chan 104 flags=0x31 maxpwr=15
adding chan 108 flags=0x31 maxpwr=15
adding chan 112 flags=0x31 maxpwr=15
adding chan 116 flags=0x31 maxpwr=15
adding chan 120 flags=0x31 maxpwr=15
adding chan 124 flags=0x31 maxpwr=15
adding chan 128 flags=0x31 maxpwr=15
adding chan 132 flags=0x31 maxpwr=15
adding chan 136 flags=0x31 maxpwr=15
adding chan 140 flags=0x31 maxpwr=15
adding chan 149 flags=0xa1 maxpwr=15
adding chan 153 flags=0xa1 maxpwr=15
adding chan 157 flags=0xa1 maxpwr=15
adding chan 161 flags=0xa1 maxpwr=15
adding chan 165 flags=0xa1 maxpwr=15
calib version=4 pa type=0 voltage=0
crystal calibration 0x00770077
iwn0: MIMO 3T3R, MoW, address xx:xx:xx:xx:xx:xx
iwn0: 11a rates: 6Mbps 9Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps
iwn0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps
iwn0: 11g rates: 1Mbps 2Mbps 5.5Mbps 11Mbps 6Mbps 9Mbps 12Mbps 18Mbps 24Mbps 
36Mbps 48Mbps 54Mbps

I believe the channels from 36 and upwards are part of the 11a
set, and should be found in the 5 GHz band.  Now, it is of course
entirely possible that this is just something that the chip
itself supports, and that the device that the chip is part of is
not wired to support these channels.  How could I get to know
that?

Furthermore, if I do 'ifconfig iwn0 mode 11a up',
and then run 'wlanctl -a | grep -B 1 freq' from time to time, I get:
        ess <>
        chan 44 freq 5220MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 1 freq 2412MHz flags 04e0<cck,ofdm,2.4GHz,dynamic cck-ofdm>
--
        ess <>
        chan 120 freq 5600MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 13 freq 2472MHz flags 06e0<cck,ofdm,2.4GHz,passive scan,dynamic 
cck-ofdm>
--
        ess <>
        chan 116 freq 5580MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 157 freq 5785MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 36 freq 5180MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 100 freq 5500MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 132 freq 5660MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 165 freq 5825MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 40 freq 5200MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 100 freq 5500MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 128 freq 5640MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 161 freq 5805MHz flags 0340<ofdm,5GHz,passive scan>
--
        ess <>
        chan 13 freq 2472MHz flags 06e0<cck,ofdm,2.4GHz,passive scan,dynamic 
cck-ofdm>

so to me it seems that the driver is cycling through the 11a
channel set trying (unsuccessfully) to find a network to which to
associate.

Any suggestions to what more I might try?  Or can someone offer
authoritative insights whether this can be made to work at all,
with our current 802.11 framework and the iwn driver?

                                        -jarle

[*]http://www.intel.com/content/dam/www/public/us/en/documents/product-briefs/ultimate-n-wifi-link-5300-brief.pdf
-- 
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