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Date: Wed, 17 Jan 2024 08:34:08 +0100
From: Sascha Hauer <s.hauer@pengutronix.de>
To: Ping-Ke Shih <pkshih@realtek.com>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
	Viacheslav <adeep@lexina.in>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
	Jernej =?iso-8859-15?Q?=A6krabec?= <jernej.skrabec@gmail.com>
Subject: Re: rtw88: rtl8822cs AP mode not working
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On Wed, Jan 17, 2024 at 12:35:42AM +0000, Ping-Ke Shih wrote:
> + Sascha for question 3)
> 
> (no other comments for now)
> 
> > -----Original Message-----
> > From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> > Sent: Wednesday, January 17, 2024 6:07 AM
> > To: Ping-Ke Shih <pkshih@realtek.com>; Viacheslav <adeep@lexina.in>
> > Cc: linux-wireless@vger.kernel.org; Jernej Škrabec <jernej.skrabec@gmail.com>
> > Subject: Re: rtw88: rtl8822cs AP mode not working
> > 
> > Hi Ping-Ke and Viacheslav,
> > 
> > On Mon, Jan 15, 2024 at 3:17 AM Ping-Ke Shih <pkshih@realtek.com> wrote:
> > [...]
> > > > > 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.
> > AP mode is also not working for me, I get the same problem as
> > Viacheslav reported.
> > 
> > > > 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.
> > Thanks for the explanation - that helped me find a better starting point!
> > 
> > I didn't have much time in the past few days, but I have some findings
> > and questions:
> > 1) I found the following comment/code in the downstream driver [0]:
> > /*
> >  * Disable Hw protection for a time which revserd for Hw sending beacon.
> >  * Fix download reserved page packet fail that access collision with
> > the protection time.
> >  */
> > val8 = rtw_read8(adapter, REG_BCN_CTRL_8822C);
> > restore[1] = val8;
> > val8 &= ~BIT_EN_BCN_FUNCTION_8822C;
> > val8 |= BIT_DIS_TSF_UDT_8822C;
> > rtw_write8(adapter, REG_BCN_CTRL_8822C, val8);
> > 
> > This is not part of the upstream rtw88 driver, so I made a patch and
> > attached it.
> > Unfortunately it doesn't fix the problem.
> > 
> > 2) PCI is the only HCI which does not need the checksum in the
> > pkt_Info (USB and SDIO need the checksum).
> > The checksum is added by rtw_tx_fill_txdesc_checksum() which is only
> > called in usb.c and sdio.c.
> > My understanding is that for reserved pages we can have more than one
> > pkt_info in the buffer (my starting point for this thought is
> > rtw_fill_rsvd_page_desc() from fw.c).
> > In usb.c and sdio.c we're only calculating the checksum for the very
> > first pkt_info, not for any subsequent ones (I didn't even know that
> > it's possible to have more than one pkt_Info outside of RX and TX
> > aggregation).
> > However, it seems that the downstream code calculates the TX checksum
> > for *all* pkt_info in the buffer, see [1]
> > This code is missing from rtw88 at the moment. Since I didn't have
> > time I did not try to implement this yet.
> > 
> > 3) Has anybody tried AP mode with rtw88 on a (supported) USB chipset?
> > If my thought (from #2) is correct then AP mode would show the same
> > problems there.

I haven't tried AP mode with the rtw88 driver. Shame on me, but I didn't
want to open that can of worms at that time.

Regards,
 Sascha

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