Re: [PATCH] rtw88: add TX power limit support to 114 and 130 channels

[Thadeu Lima de Souza Cascardo <cascardo@igalia.com>]

On Mon, Apr 13, 2026 at 05:56:17AM +0000, Ping-Ke Shih wrote:
> Thadeu Lima de Souza Cascardo <cascardo@igalia.com> wrote:
> > On Fri, Apr 10, 2026 at 03:56:11AM +0000, Ping-Ke Shih wrote:
> > > Thadeu Lima de Souza Cascardo <cascardo@igalia.com> wrote:
> > > > Though 114 and 130 are not usual channels, they are found in the wild with
> > > > setups using 5350MHz as the center frequency of a 80MHz setup.
> > >
> > > What did the AP setup? channel 114 160MHz?
> > > I wonder why rtw88 can select a not usual channel 114 80MHz.
> > >
> > > Please share your environment setup.
> > >
> > 
> > This is a Mikrotik that uses channel 130 at 80MHz.
> 
> I'm surprised that an AP can work on this not usual channel/bandwidth. 
> Can you change the setting to usual channel/bandwidth? We'd avoid using
> this unsupported channel/bandwidth by [1].
> 

It seems to be "well-known" that some APs do it and it has caused other
issues in other drivers. But it works just fine with a lot of other
drivers. So, I would rather make rtw88 work with that setting, even if it
falls back to 40MHz, for example.

Let me check what happens when using the proposed patch and I will report
back to you.

> > 
> > > >
> > > > rtw88 supports that, but issues a WARNING because it cannot find the TX
> > > > power limit for those channels.
> > >
> > > Actually, rtw88 hardware can't support that, so we are working on patch
> > > to avoid selecting unusual channels. Can it work properly with
> > > the AP after this patch?
> > >
> > 
> > It does work just fine even without the patch. The only issue is the
> > WARNING that is triggered.
> > 
> 
> As internal discussion, hardware doesn't work on channel 130 80M,
> which means connection might be well, but it can't yield expected performance.
> More, the power limit is not really verified on ch130 80M, so we wonder
> that the signal might not in expectation.
> 

The rationale behing my patch was exactly to try to set the power limit to
the lesser one of the adjacent channels. I am not sure that the expected
performance was not achieved. How would you suggest that I verify?

Thanks a lot.
Cascardo.

> By above reasons, we'd avoid using channel 114 and 130.
> 
> [1] https://lore.kernel.org/linux-wireless/20260413053601.13037-1-pkshih@realtek.com/T/#u
> 
>