brcmfmac: error messages while entering suspend

[Stefan Wahren <wahrenst@gmx.net>]

Hi,
I'm currently working on s2idle support for Raspberry Pi 3B+ (BCM43455
SDIO). During the tests with I noticed harmless, but annoying error
messages from brcmfmac like this:

[  383.186640] PM: suspend entry (s2idle)
[  383.190107] Filesystems sync: 0.003 seconds
[  383.247470] Freezing user space processes
[  383.250291] Freezing user space processes completed (elapsed 0.002
seconds)
[  383.250379] OOM killer disabled.
[  383.250385] Freezing remaining freezable tasks
[  383.251677] Freezing remaining freezable tasks completed (elapsed
0.001 seconds)
[  384.292071] ieee80211 phy0: brcmf_fil_cmd_data: bus is down. we have
nothing to do.
[  384.292079] ieee80211 phy0: brcmf_cfg80211_get_tx_power: error (-5)

These errors are not new and I assume they have always been there. I'm
not an expert here, so I want to know is the problem here that the SDIO
interface is shutdown before brcmfmac is suspended or lies the issue
within brcmfmac suspend itself?

Here is a calltrace for the error above:

[  384.291308]  brcmf_fil_cmd_data+0xe0/0x114 [brcmfmac] (P)
[  384.291347]  brcmf_fil_iovar_data_get+0xcc/0x134 [brcmfmac] (L)
[  384.291384]  brcmf_fil_iovar_data_get+0xcc/0x134 [brcmfmac]
[  384.291420]  brcmf_cfg80211_get_tx_power+0x58/0xd4 [brcmfmac]
[  384.291458]  nl80211_send_iface+0x1e8/0x584 [cfg80211]
[  384.291549]  nl80211_notify_iface+0x58/0xd4 [cfg80211]
[  384.291615]  _cfg80211_unregister_wdev+0x40/0x27c [cfg80211]
[  384.291682]  cfg80211_unregister_wdev+0x14/0x20 [cfg80211]
[  384.291748]  brcmf_p2p_ifp_removed+0x6c/0x98 [brcmfmac]
[  384.291785]  brcmf_remove_interface+0x170/0x1ec [brcmfmac]
[  384.291822]  brcmf_detach+0x60/0xfc [brcmfmac]
[  384.291859]  brcmf_sdio_remove+0x4c/0x188 [brcmfmac]
[  384.291896]  brcmf_sdiod_remove+0x24/0xa4 [brcmfmac]
[  384.291933]  brcmf_ops_sdio_suspend+0x100/0x1c8 [brcmfmac]
[  384.291971]  pm_generic_suspend+0x2c/0x44
[  384.291982]  dpm_run_callback.constprop.0+0x74/0x134
[  384.291993]  device_suspend+0x110/0x3d0
[  384.292002]  async_suspend+0x24/0x3c
[  384.292012]  async_run_entry_fn+0x34/0xe0
[  384.292022]  process_one_work+0x150/0x294
[  384.292032]  worker_thread+0x2dc/0x3dc
[  384.292041]  kthread+0x118/0x11c
[  384.292049]  ret_from_fork+0x10/0x20

Best regards