Power save setting while interface is down

[James Prestwood]

Hi Kalle,

On 11/21/23 06:15, Kalle Valo wrote:
> James Prestwood <prestwoj at gmail.com> writes:
>
>> Hi,
>>
>> I've noticed a somewhat rare behavior (<1% of the time) where bringing
>> an interface up fails after disabling power save. This is done by IWD
>> when a user-option is enabled, and follows an interface
>> removal/creation. The sequence is:
>>
>> 1. Remove default interface
>>
>> 2. Create new interface
>>
>> 3. Disable power save on new interface
>>
>> 4. Bring up new interface (rarely fails with -110).
>>
>> iwd[1286641]: src/netdev.c:netdev_disable_ps_cb() Disabled power save
>> for ifindex 54
>> kernel: ath10k_pci 0000:02:00.0: wmi service ready event not received
>> iwd[1286641]: Error bringing interface 54 up: Connection timed out
>> kernel: ath10k_pci 0000:02:00.0: Could not init core: -110
> So I guess you have a test setup to reproduce this easily? How long does
> it take to see this?

It really depends. I was letting IWD do the work and waiting excessively 
which could sometimes take an hour. But I managed to get it to happen 20 
seconds apart using ip/iw in a loop. On average it usually happens 
within 5-10 minutes, sometimes sooner.

$ dmesg --follow & $ for i in $(seq 1 4000); do sudo ip link set wlan0 
down; sudo iw dev wlan0 set power_save off; sudo ip link set wlan0 up; done

[ 882.927218] ath10k_pci 0000:02:00.0: wmi service ready event not 
received RTNETLINK answers: Connection timed out [ 883.016550] 
ath10k_pci 0000:02:00.0: Could not init core: -110 [ 904.434930] 
ath10k_pci 0000:02:00.0: wmi service ready event not received RTNETLINK 
answers: Connection timed out [ 904.524287] ath10k_pci 0000:02:00.0: 
Could not init core: -110

> What hardware and firmware version are you using?
[    5.680909] ath10k_pci 0000:02:00.0: qca6174 hw3.2 target 0x05030000 
chip_id 0x00340aff sub 1dac:0261
[    5.680921] ath10k_pci 0000:02:00.0: kconfig debug 0 debugfs 1 
tracing 1 dfs 0 testmode 0

[    5.681607] ath10k_pci 0000:02:00.0: firmware ver 
WLAN.RM.4.4.1-00309- api 6 features wowlan,ignore-otp,mfp crc32 0793bcf2

I've seen this on 00241, 00288, and the latest firmware above.

>> I'm thinking maybe there is a race between creating the fresh
>> interface and disabling PS, then bringing the interface back up?
> Yeah, looks like it. If it's relatively easy for you to reproduce this
> you could try adding delays to suitable spots in ath10k. That might be
> give more ideas where the race is exactly.

Ok, I can add a delay ahead of the WMI request that's timing out and see 
what happens.

>
>> Setting PS after the interface is up (so far) seems to be 100%
>> reliable and have not yet seen this behavior. Regardless of any kernel
>> fixes I'll need to reorder the command sequence in IWD to support
>> existing kernels, but before I work around this issue I wanted to
>> point it out so its not hidden from view.
> To me working around this in user space doesn't sound like a good idea.
> I would rather have a workaround in the kernel (but obviously I hope we
> can find a proper fix).

Yep, totally agree.

Thanks,

James