RE: [PATCH rtw-next] wifi: rtw88: 8822b: Relax ETSI EDCCA threshold on 2.4 GHz

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

Josef Schlehofer <pepe.schlehofer@gmail.com> wrote:
> The RTL8822B has no firmware-managed adaptivity, so rtw88 sets
> the EDCCA thresholds in the driver. Under ETSI, the current rule
> uses L2H = min(IGI, 36), at most about -74 dBm.
> 
> On a TP-Link Archer T4U v3 (RTL8812BU) operating as a 2.4 GHz AP,
> in-band energy, mostly from the adapter's own USB 3 link, kept IGI
> at 0x2a and L2H at 36. The AP was not seen in any of 5 scans, and
> the driver reported "failed to get tx report from firmware".
> 
> With min(max(IGI + 8, 48), 50), the AP was seen in 4/5 scans on the
> same port and boot (16/19 across repeated runs), with no TX report
> failures and no change in the false alarm rate.
> 
> EN 300 328 V2.2.2 tests detection at -70 dBm/MHz for a 20 dBm EIRP
> transmitter, about -57 dBm over 20 MHz.
> 
> Use the normal threshold, max(IGI + 8, 48), on 2.4 GHz under ETSI,
> capped at 50 (nominally -60 dBm). Keep the existing rule on 5 GHz
> and in JP.
> 
> Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>

Acked-by: Ping-Ke Shih <pkshih@realtek.com>

[...]

> +/* nominally -60 dBm: 3 dB below the EN 300 328 level at 20 dBm e.i.r.p. */
> +#define RTW8822B_EDCCA_ETSI_2G 50

For the record, I consulted internally that the hardware isn't very accurate,
but with 3 dB reduction, it should be fine.