Problem with iw set bitrate in ath10k

[Michal Kazior]

On 20 June 2015 at 00:01, Ilias Syrigos <ilias013 at gmail.com> wrote:
> Hello,
>
> I'm trying to fix the bitrate with the iw set bitrates command.
>
> More specifically, I want to use single stream rates (nss=1) and let
> the driver choose the mcs. So, I use:
>
> iw wlan0 set bitrates legacy-5 ht-mcs-5 vht-mcs-5 1:0-9
>
> With this setting I observe successful transmissions with nss=2 and
> rate_index=9, through monitor mode at the receiving node, and iperf
> throughput of 300 Mbps.
>
> Why is nss not fixed to 1?

That's interesting. Are you associated in VHT or HT mode? Can you get
some logs, please? [1] (traces preferred)

[1]: https://wireless.wiki.kernel.org/en/users/drivers/ath10k/debug

Generally firmware rate-control is really picky when it comes to
configuration. I recall I had observed some quirkiness when I was
working on extending the set_bitrate_mask callback.


> Moreover, before using the iw command to fix the rate, driver uses
> nss=2 and rate_index=4.
>
> Shouldn't have been also 2:9 (nss=2, rate_index=9)?
>
> In addition, when I manually fix the rate with the:
>
> iw wlan0 set bitrates legacy-5 ht-mcs-5 vht-mcs-5 2:9  or even 2:8
>
> I cannot receive anything and I notice too many fcs errors.

VHT rates 8 and 9 can be pretty demanding when it comes to signal
quality. You might need to change antenna positioning on both receiver
and transmitted devices to get it working.


> I'm only able to receive at the fixed 2:7.
>
> I'm using the latest development driver and the latest firmware-5.

This isn't firmware version per se. This is just an ABI wrapper
version and doesn't imply firmware revision. Take a look at dmesg,
please.


Michał