On 1/19/23 09:35, Richard Fitzgerald wrote: > On 19/1/23 14:48, Pierre-Louis Bossart wrote: >> >>>>> +static int cs42l42_sdw_dai_startup(struct snd_pcm_substream >>>>> *substream, >>>>> + struct snd_soc_dai *dai) >>>>> +{ >>>>> + struct cs42l42_private *cs42l42 = >>>>> snd_soc_component_get_drvdata(dai->component); >>>>> + >>>>> + if (!cs42l42->init_done) >>>>> + return -ENODEV; >>>> >>>> Can this happen? IIRC the ASoC framework would use >>>> pm_runtime_resume_and_get() before .startup, which would guarantee that >>>> the device is initialized, no? >>>> >>> >>> Yes, this can happen. Because of the way that the SoundWire enumeration >>> was implemented in the core code, it isn't a probe event so we cannot >>> call snd_soc_register_component() on enumeration because -EPROBE_DEFER >>> wouldn't be handled. So the snd_soc_register_component() must be called >>> from probe(). This leaves a limbo situation where we've registered the >>> driver but in fact don't yet have any hardware. ALSA/ASoC doesn't know >>> that we've registered before we are functional so they are happy to >>> go ahead and try to use the soundcard. If for some reason the hardware >>> failed to enumerate we can get here without having enumerated. >> >> Humm, yes, but you've also made the regmap cache-only, so is there >> really a problem? >> > > It's true that normally we go past these stages in cache-only, but that > is because normally (non-Soundwire) we already initialized the hardware > to good state during probe(). > If we just carry on when it hasn't enumerated and we haven't initialized > it yet, who knows what will happen if it enumerates some time later. > > We could just ignore it and see if anyone has a problem but for the sake > of a couple of lines of code I feel like I'd rather check for it. > >> FWIW I don't see a startup callback in any other codec driver. It may be >> wrong but it's also a sign that this isn't a problem we've seen so far >> on existing Intel-based platforms. >> > > 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'.