After upgrading tumbleweed, system suspend stopped working because of failing
to enter PM state. 

dmesg excerpt:

[44812.779354] brcmfmac 0000:02:00.0: brcmf_pcie_pm_enter_D3: Timeout on
response for entering D3 substate
[44812.779365] PM: pci_pm_suspend(): brcmf_pcie_pm_enter_D3+0x0/0x140
[brcmfmac] returns -5
[44812.779468] PM: dpm_run_callback(): pci_pm_suspend+0x0/0x160 returns -5
[44812.779486] brcmfmac 0000:02:00.0: PM: failed to suspend async: error -5
[44812.779642] PM: Some devices failed to suspend, or early wake event detected


sudo lshw -C Network
  *-network                 
       description: Wireless interface
       product: BCM43602 802.11ac Wireless LAN SoC
       vendor: Broadcom Inc. and subsidiaries
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: wlp2s0
       version: 01
       serial: 40:49:0f:fe:d3:4b
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical
wireless
       configuration: broadcast=yes driver=brcmfmac driverversion=7.35.177.61
firmware=01-ea662a8c ip=192.168.0.2 latency=0 multicast=yes wireless=IEEE
802.11
       resources: irq:136 memory:dd800000-dd807fff memory:dd400000-dd7fffff


More related kernel logs at the beginning:

dmesg | grep brcmfmac
[    4.290886] usbcore: registered new interface driver brcmfmac
[    4.290936] brcmfmac 0000:02:00.0: enabling device (0000 -> 0002)
[    4.399941] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43602-pcie
for chip BCM43602/1
[    4.400915] brcmfmac 0000:02:00.0: Direct firmware load for
brcm/brcmfmac43602-pcie.Dell Inc.-XPS 15 9550.bin failed with error -2
[    4.443495] brcmfmac 0000:02:00.0: Direct firmware load for
brcm/brcmfmac43602-pcie.Dell Inc.-XPS 15 9550.txt failed with error -2
[    4.443518] brcmfmac 0000:02:00.0: Direct firmware load for
brcm/brcmfmac43602-pcie.txt failed with error -2
[    4.965032] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43602-pcie
for chip BCM43602/1
[    4.965053] brcmfmac: brcmf_c_process_clm_blob: no clm_blob available
(err=-2), device may have limited channels available
[    4.965653] brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM43602/1 wl0: Nov
10 2015 06:38:10 version 7.35.177.61 (r598657) FWID 01-ea662a8c




locate 'brcm/brcmfmac43602'                               
/usr/lib/firmware/brcm/brcmfmac43602-pcie.ap.bin.xz
/usr/lib/firmware/brcm/brcmfmac43602-pcie.bin.xz

What I don't get is why does it try to load "brcm/brcmfmac43602-pcie.Dell
Inc.-XPS 15 9550.bin" that is of course missing?