Raspberry Pi Zero 2 W: BCM43430/2 firmware does not support 4-way handshake offloading

[stapelberg]

It seems like there are (at least) two different Raspberry Pi Zero 2 W revisions on the market, and they differ in terms of which WiFi chip is used.

The BCM43430/1 works as expected, and seems to match the chip used on the Raspberry Pi 3 B.

The BCM43430/2 however requires different firmware files (brcmfmac43436). This firmware unfortunately lacks support for 4-way handshake offloading, as can be verified by running iw phy, which prints:

	Supported extended features:
		* [ CQM_RSSI_LIST ]: multiple CQM_RSSI_THOLD records

…whereas on the BCM43430/1, Raspberry Pi 3B, 3B+ or 4B, it prints:

	Supported extended features:
		* [ CQM_RSSI_LIST ]: multiple CQM_RSSI_THOLD records
		* [ 4WAY_HANDSHAKE_STA_PSK ]: 4-way handshake with PSK in station mode
		* [ 4WAY_HANDSHAKE_STA_1X ]: 4-way handshake with 802.1X in station mode
		* [ SAE_OFFLOAD ]: SAE offload support

The 4-way handshake offloading is not just a performance optimization, but rather the feature that made using encrypted WiFi possible at all on platforms like https://gokrazy.org/ (not based on Raspberry Pi OS, entirely implemented in Go aside from the Linux kernel). With the offloading, connecting to WiFi is as simple as one Linux nl80211 API call, whereas without the offloading, a lot of work is required in userspace (wpa_supplicant).

Is the lack of 4-way handshake offloading an oversight in the current firmware blobs for the BCM43430/2?

Is there any chance we could get a fixed firmware version?

Thanks in advance

(PS: we figured this out in gokrazy/gokrazy#96, but I’m filing a separate issue as the history is getting lengthy…)

[pelwell]

Thanks for collating the significant details in one place. A ticket has been opened with Synaptics.

[stapelberg]

Thanks, Phil! I appreciate it.

[joneskoo]

@pelwell In the meanwhile, do you have information how we can identify Zero 2 W with each chip so we can document compatibility?

[pelwell]

The chips are featureless and under the metal cap of the module so there is no visible difference, and the firmware doesn't know - the board revisions are identical; only the kernel can tell after probing the SDIO bus when booting. The best way to tell which version you have to is to boot it up and type:

$ dmesg | grep "Firmware: BCM43430"

If the output includes BCM43430/2 (corresponding to the brcmfmac43436-sdio firmware) the part is affected by this issue.
If the output includes BCM43430/1 (corresponding to the brcmfmac43436s-sdio firmware) then the part is not affected.

[pelwell]

Synaptics have given us a trial firmware. It appears to make the right noises:

        Supported extended features:
                * [ 4WAY_HANDSHAKE_STA_PSK ]: 4-way handshake with PSK in station mode
                * [ 4WAY_HANDSHAKE_STA_1X ]: 4-way handshake with 802.1X in station mode
                * [ SAE_OFFLOAD ]: SAE offload support

The version message at boot is:

[    8.450230] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43436-sdio for chip BCM43430/2
[    8.508391] brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM43430/2 wl0: Mar 29 2022 19:22:43 version 9.88.4.77 (g58bc5cc) FWID 01-623162e

You will have to rename the firmware when you install it, but I don't think you'll struggle with that...

https://drive.google.com/file/d/1_q2aXxBV5PTUSVAE2crt4uqfjbN9ebN3/view?usp=sharing

[stapelberg]

Thanks for relaying the trial firmware!

I have just verified it on my Raspberry Pi Zero 2 W, and it indeed works! I can now connect to encrypted WiFi, too.

This is great news. Thanks so much for your help!

[pelwell]

There should be an official release next week.

[macmpi]

@pelwell would you expect Synaptics to finally make such release in upstream linux-firmware, or would that be only from Raspberry Pi Ltd at this stage?
Did you manage to get an update on the License file as per raspberrypi/linux#4723 (comment)
Thanks.

[pelwell]

I don't expect this release to change anything about the way Synaptics choose to distribute (or not) their firmwares.

The Licence issue is still ongoing - they have provided some words, but they make it sound as if people are not free to redistribute the firmware, which they are. It's almost as if lawyers get paid by the hour.

[pelwell]

There's an official release from Synaptics available here: https://github.com/RPi-Distro/firmware-nonfree/blob/fdaf74c780ca7a29b12d62e5b0d37c38c2321e20/debian/config/brcm80211/brcm/brcmfmac43436-sdio.bin
This will become part of the next apt package release unless a regression is found.