ath10k: Wifi slow on the XPS13 (9360) (QCA6174)

[Kalle Valo]

+ linux-wireless and cleaning the subject

Hi Thorsten,

sorry for the late reply, I'm having problems keeping up with all the
email. I just do a quick reply now to point out that you are talking
about two different problems. To keep the discussion simple I recommend
keeping the two issues complete separate.

Thorsten Leemhuis <linux at leemhuis.info> writes:

> Lo! Splitting this thread to focus on a issue that has nothing to do
> with the regression in 4.14 I reported:
>
> On 03.10.2017 01:40, Ryan Hsu wrote:
>> On 10/01/2017 01:59 AM, Thorsten Leemhuis wrote:
>>>> ath10k_pci 0000:3a:00.0: Direct firmware load for
>>>> ath10k/pre-cal-pci-0000:3a:00.0.bin failed with error -2
>>>> ath10k_pci 0000:3a:00.0: Direct firmware load for
>>>> ath10k/cal-pci-0000:3a:00.0.bin failed with error -2
>>> Do they have anything to do with this? Hardware is
>> This error message is confusing since QCA6174 is not supporting
>> pre-calibration feature, this reminds me that we need to clean this up.
>
> I guess that would be good to avoid confusion. But while at it: If you
> have a minute, could you please explain to me how to properly set up the
> wifi firmware files for my Dell XPS13 (9360)? The reasons why I'm
> asking: Sending data via wifi is really slow on my laptop (scp copies
> only get 2 to 5 MByte/s on networks that are known to be a lot faster).
> I wonder if the firmware files or the calibration data is part of the
> reason wifi Tx is slow. The machine is normally shipped with a slightly
> enhanced Ubuntu 16.04. That among others contains a package with the
> machine specific files board.bin and board-2.bin that replace the files
> normally installed in /lib/firmware/ath10k/QCA6174/hw3.0/ Are those
> machine specific files crucial to have or are the one from the
> linux-firmware repo good enoguh? I'm using Fedora and could copy the
> ones from Ubuntu over, but obviously they will get overwritten every
> time Fedora ships a new linux-firmware package – IOW: every few weeks :-/

Yes, the board file can affect throughtput, _both_ TCP and UDP. I don't
know what board files Ubuntu is shipping but we should try to get those
into upstream.

> Side note: You find a lot of reports about slow wifi is you search the
> net with terms like "9360 wifi slow linux". Ubuntu fixed that a few
> months ago with this patch:
> http://kernel.ubuntu.com/git/ubuntu/ubuntu-xenial.git/commit/?id=9690f19f07fee2acb2b04ea5eaa5db184ee175d5
>
> Some bugs about this:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1692836
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1670041

But this again about interraction between ath10k and TCP stack. And it
_only_ affects TCP, UDP should be unaffected. So whenever testing
throughput please always measure both TCP and UDP because then it's
easier to pinpoint the reason.

> But from what I gathered by searching the net and asking on #ath10k I
> got the impression that patch is a massive ugly hack and no way
> acceptable upstream.  Is that correct?

Yes, it's a horrible hack and I cannot apply that. And like you said
#1692836, also Eric Dumazet (one of TCP maintainers) agrees with that.

> If yes: is there maybe a proper fix out there somewhere?

Unfortunately there still is no good solution. In a week there's Netdev
2.2 and we have Linux Wireless summit there. We should bring up this
topic there.

-- 
Kalle Valo