On Wed, Apr 5, 2017 at 4:54 AM, Arnaud Mouiche <arnaud.mouiche@xxxxxxxxxxx> wrote: > Good catch. All of this makes sense. > The SSI surely detect a glitch at the start of the stream and takes it for a > sync frame, but not followed by the expected 32x2 bits. > It also explain why Caleb and I are not able to reproduce, since we connect > SSI internally using the audmux, leaving no place for such glitch. > > If only Max can validate this fix... Yes, that would be nice. > But what is strange is that writing TE and EN at once also avoid the > issue... or it means the issue was really timing dependent. > > Do you know which one is started first ? > - fsl_ssi_trigger(SNDRV_PCM_TRIGGER_START) > or > - stgl5000 PCM bus being turned on > > We can expect that stgl5000 turns the PCM clocks first, and then SSI is > turned on. Otherwise anything can happened when the codec starts its > clocking. Correct: stgl5000 turns the PCM clocks first. > Maybe we should look at the Fsync state when idle, and see how it behave > during the startup. Depending of pull-up /down-down configuration of the > pads, it may be leaved in a undefined state with undefined transitions when > stgl5000 turns its output on... > > Another way to definitively fix this kind of issue is to use > SND_SOC_DAIFMT_CBS_CFS > - the codec generates the N*8*64 kHz or 44.1*64 kHz precise bitclock > (something which is not flexible for the SSI who is connected to a fix PLL > output clock) > - but the SSI generate the Sync, leaving no place for wrong detection. > Unfortunately, stgl5000 doesn't seem to support this mode. Correct. I plan to submitting a sgtl5000 patch that allows setting the lrclk pad strength via device tree. Will wait for Max to confirm if this solves the swap channel issue on his board as well. I would like to thank you and Caleb for the tests. Glad to see your atest application working as expected with the SSI driver :-) _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
