rtw89: RTL8851B BTC entry requires unpublished firmware 0.29.133.0

rtw89: RTL8851B BTC entry requires unpublished firmware 0.29.133.0

[Maxim Skokov]

Hi,

While reading the Wi-Fi/Bluetooth coexistence code in rtw89 I noticed a
BTC version entry for RTL8851B that appears to be unreachable with any
firmware currently available in linux-firmware.

In drivers/net/wireless/realtek/rtw89/coex.c, rtw89_btc_ver_defs[] has
two entries for this chip:

  {RTL8851B, RTW89_FW_VER_CODE(0, 29, 133, 0), ... .fcxtrx = 107, ...}
  {RTL8851B, RTW89_FW_VER_CODE(0, 29,  29, 0), ... .fcxtrx = 0,   ...}

rtw89_coex_recognize_ver() walks the table and selects the first entry
whose fw_ver_code is not greater than the loaded firmware version.

The newest firmware published for this chip in linux-firmware is
0.29.41.5 (rtw89/rtw8851b_fw.bin, updated 2025-11-06; rtw8851b_fw-1.bin
added 2026-02-13).  Since 41 < 133, the 0.29.133.0 entry can never be
selected, and every user loading firmware from linux-firmware ends up on
the legacy 0.29.29.0 profile.

On my RTL8851BE with firmware 0.29.41.3 the driver does fall back to the
legacy entry, as expected:

  [BTC] use version def[2] = 0x001d1d00

To be clear, I am not reporting a malfunction.  I have not observed any
concrete problem that I can attribute to this, and the legacy profile may
well be perfectly adequate.  I simply cannot tell how the situation is
meant to be read:

  - Is firmware 0.29.133 or newer expected to reach linux-firmware at
    some point, with the driver support having landed ahead of it?

  - Or is the version code in that entry not what was intended?

Either answer is fine, I would just like to understand it.  I have the
hardware and a debug build available, so I am happy to test or collect
logs if that would help.

Thanks,
Maxim Skokov

RE: rtw89: RTL8851B BTC entry requires unpublished firmware 0.29.133.0

[Ping-Ke Shih]

Maxim Skokov <skokovmaksimevg@gmail.com> wrote:
> To be clear, I am not reporting a malfunction.  I have not observed any
> concrete problem that I can attribute to this, and the legacy profile may
> well be perfectly adequate.  I simply cannot tell how the situation is
> meant to be read:
> 
>   - Is firmware 0.29.133 or newer expected to reach linux-firmware at
>     some point, with the driver support having landed ahead of it?

This one.

When BTC expert does upgrade, he does review and implement the changes
across chips in one go, because the firmware is share to many chips. 
Or, he will review the changes again and again. 

Ping-Ke

Re: rtw89: RTL8851B BTC entry requires unpublished firmware 0.29.133.0

[Maxim Skokov]

Ping-Ke Shih <pkshih@realtek.com> wrote:
> >   - Is firmware 0.29.133 or newer expected to reach linux-firmware at
> >     some point, with the driver support having landed ahead of it?
>
> This one.
>
> When BTC expert does upgrade, he does review and implement the changes
> across chips in one go, because the firmware is share to many chips.
> Or, he will review the changes again and again.

Understood, thanks for explaining.  Good to know the table is meant to
run ahead of the published firmware rather than the other way round, and
that the entries land per-chip in one batch.

Thanks,
Maxim