Hello Mark, On 04/26/2017 06:15 PM, Mark Brown wrote: > On Thu, Apr 13, 2017 at 08:01:34AM +0000, Olivier MOYSAN wrote: > >> 1) 2 static dais NOT exclusive >> - dai tx >> - dai rx >> The IP exhibits a mode register, where you select mode TX, RX or FD. >> There are 2 two options to manage this register. >> option 1: >> start first channel with mode RX or TX >> when second channel is started, mode has to be changed to FD. >> Transfers have to be stopped before changing configuration >> registers, so this leads to cuts in audio stream. >> option 2: >> start a first channel with mode FD. >> In this case, we may have unpredictable behavior for the stream >> which is not already started. probably underrun/overrun. >> So, this solution rises problem for full-duplex management. > >> 2) 3 static dais exclusive >> - dai tx >> - dai rx >> - dai rx-tx (fd) >> This is the current implementation. >> The choice of the dai is done at probe time. It is provided by DT >> through sound-dai parameter. >> When dai fd is selected, after starting first stream, we assume that >> second stream will be started. In this case we wait for second stream >> to be available before enabling IP and starting transfers. > >> 3) 1 dynamic dai >> - dai rx or tx or fd (according to dma conf in IP node) >> Here the driver exposes only a single dai constructed from dma >> configuration provided by IP DT node. >> This allows to get ride of sound-dai parameter. > > None of these options reflect how normal I2S controllers present > themselves in DT. To repeat, you should present a single bidirectional > DAI for the single physical bidirectional I2S controller that your > hardware has. > > If it's not possible to figure out a way to make the controller support > simultaneous playback and record with the two started independently then > the driver should just return an error if userspace tries to start the > second direction up. This will severely limit the utility of the driver > as Linux generally treats playback and record independently but that's > going to apply just as much with any of the options involving multiple > DAIs or configuration in DT. You might be able to do something with > feeding it dummy data I guess? > Ok. I will implement a single bidirectional DAI in v2. Best regards Olivier -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
