It looks like this:
root@ap4evb:~# modprobe b43
[ 36.023437] cfg80211: Calling CRDA to update world regulatory domain
[ 36.460937] sdio_bus_probe()
[ 36.468750] sdio_bus_probe() calling pm_runtime_get_sync()
[ 36.468750] mmc_power_restore_host() begin
[ 36.570312] mmc_sdio_power_restore() begin
[ 36.570312] mmc_sdio_init_card()
[ 36.578125] mmc_sdio_init_card() mmc_send_io_op_cond ret=-110
[ 36.585937] mmc_sdio_power_restore() end ret=-110
[ 36.593750] mmc_power_restore_host() end ret=-110
[ 36.593750] sdio_bus_probe() pm_runtime_get_sync ret=-16
[ 36.601562] b43-sdio: probe of mmc0:0001:1 failed with error -16
So it seems to fail in mmc_sdio_init_card at the mmc_send_io_op_cond()
call.
Actually nothing special happens after sdio_bus_probe()
With your patch the problem goes away, thanks.
Regards,
Arnd
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