RE: rtw88: rtl8822cs AP mode not working

[Ping-Ke Shih <pkshih@realtek.com>]

> -----Original Message-----
> From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> Sent: Sunday, January 14, 2024 6:50 AM
> To: Ping-Ke Shih <pkshih@realtek.com>
> Cc: Viacheslav <adeep@lexina.in>; linux-wireless@vger.kernel.org; Jernej Škrabec
> <jernej.skrabec@gmail.com>
> Subject: Re: rtw88: rtl8822cs AP mode not working
> 
> Hi Ping-Ke,
> 
> On Fri, Jan 12, 2024 at 1:40 AM Ping-Ke Shih <pkshih@realtek.com> wrote:
> [...]
> > > dmesg/journalctl is clean. No messages related to wifi.
> > >
> >
> > Have you ever tried AP mode on SDIO interface wifi cards, like RTL8822CS?
> > It seems no beacon issues properly, but no obvious errors during starting
> > AP mode.
> I haven't tried AP mode before (and I think* that Jernej also hasn't tried it).
> 
> > I don't have this kind of wifi cards, could you help to check if AP mode
> > works in your side?
> I'll check that in the next few days.
> Also I'm wondering where code enables beacons (is it
> rtw_core_enable_beacon() or is there another relevant function?).
> Knowing that would be helpful to analyze this further.
> 

The main function to get and set beacon template to firmware is 
rtw_fw_download_rsvd_page(). The basic concept is to put beacon frame via 
qsel=BCN to a special TX FIFO area called "reserve page", and then
hardware/firmware will send beacon in interval of 100ms. 

The TX FIFO look like

    +---------+
    |         |    ^
    |         |    |
    |         |    |
    |         |    | normal TX FIFO page 
    |         |    |
    |         |    |
    |         |    v 
    +---------+ <-----------  BCN_HEAD
    |         |    ^
    |         |    | reserve page
    |         |    v
    +---------+

The initial pages of reserve page is to store beacon, but latter one could be
PS null frame that firmware uses it to notify AP. 

Ping-Ke