wlan0 device sometimes not available

[Emanuel_T]

Hi,

I'm building a yocto (kirkstone branch) system for a Freescale i.MX6 Quad/DualLite System.

Previously we used a yocto sumo, now upgrading. Including Linux from 4.9 to 5.15.

The wlan0 seems not always working. With Linux 4.9 we used the bcmdhd driver. But it's not available with 5.15. anymore. Seems the BRCMFMAC is the successor?

Dmesg shows this, when it's working:

[    7.936385] brcmfmac: F1 signature read <at>0x18000000=0x15264345
[    7.946237] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio for chip BCM4345/6
[    7.960912] usbcore: registered new interface driver brcmfmac
[    8.207255] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio for chip BCM4345/6
[    8.221676] brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM4345/6 wl0: Apr 15 2021 03:03:20 version 7.45.234 (4ca95bb CY) FWID 01-996384e2

wlan0 is only available after cold boot. After rebooting, the wlan0 does not exist anymore.

When it's available I can scan for available networks.

Any idea what is causing this?

[Emanuel_T]

While developing I installed new firmware (linux-firmware-bcm43455 package). This seemed to be the problem.
When I switched back to the old firmware that worked before, placing it in the place the driver was looking for (see dmesg output, similar to this: https://github.com/raspberrypi/linux/issues/2087) wlan0 device was available again. Always.

I still need the linux-firmware-bcm43455 package, otherwise I would see warnings like this:

brcmfmac: brcmf_c_process_clm_blob: no clm_blob available

The old firmware does not have such a "clm" file.