>>> It's nicer to do the check in startup() because then the application >>> open() will fail cleanly. We could delay until prepare - which is the >>> point we really need the hardware to be accessible - and hope the >>> hardware enumerated and initialized by that time. But that's not so >>> nice from the app point of view. >> >> Another way to avoid problems is to rely on the codec component .probe >> to check if the SoundWire device is initialized before registering a >> card. >> >> I just tried with a system where the ACPI info exposes a codec which is >> not connected, it fails nicely. That avoids the pitfalls of creating a >> card which isn't functional since all dependencies are not met. >> >> [ 64.616530] snd_soc_sof_sdw:mc_probe: sof_sdw sof_sdw: Entry >> [ 64.616549] snd_soc_sof_sdw:log_quirks: sof_sdw sof_sdw: quirk >> SOF_SDW_PCH_DMIC enabled >> [ 64.616559] snd_soc_sof_sdw:sof_card_dai_links_create: sof_sdw >> sof_sdw: sdw 2, ssp 0, dmic 2, hdmi 0 >> [ 64.616587] snd_soc_sof_sdw:init_dai_link: sof_sdw sof_sdw: create >> dai link SDW0-Playback, id 0 >> [ 64.616600] snd_soc_sof_sdw:init_dai_link: sof_sdw sof_sdw: create >> dai link SDW0-Capture, id 1 >> [ 64.616607] snd_soc_sof_sdw:init_dai_link: sof_sdw sof_sdw: create >> dai link dmic01, id 2 >> [ 64.616614] snd_soc_sof_sdw:init_dai_link: sof_sdw sof_sdw: create >> dai link dmic16k, id 3 >> [ 69.757115] rt5682 sdw:0:025d:5682:00: Initialization not complete, >> timed out >> [ 69.757128] rt5682 sdw:0:025d:5682:00: ASoC: error at >> snd_soc_component_probe on sdw:0:025d:5682:00: -110 >> [ 69.757224] sof_sdw sof_sdw: ASoC: failed to instantiate card -110 >> [ 69.757734] sof_sdw sof_sdw: snd_soc_register_card failed -110 >> >> see >> https://elixir.bootlin.com/linux/latest/source/sound/soc/codecs/rt5682.c#L2927 >> >> I think this is compatible with the device model and bind/unbind, but it >> could be improved with the removal of the wait if we had a way to return >> -EPROBEDEFER, and have a mechanism to force the deferred probe work to >> be triggered when a device actually shows up. It's a generic problem >> that the probe cannot always be a synchronous function but may complete >> 'later'. > > I see what you've done in your patch, but I had already experimented > with this idea and found that the wait_for_completion() can deadlock the > Soundwire core. That's not good. Do you have any logs or explanation on what the root-cause of this deadlock might be? If something's broken, we might as well fix it.
