Add Shengjiu. On Fri, Oct 30, 2015 at 09:45:32AM +0100, arnaud.mouiche@xxxxxxxxxxx wrote: > >At imx50 age, I remember one workaround was to fill the fifo > >manually, writing directly a number of samples (equal to the > >number of slots for one frame to keep the synchronization), and > >then, enable the TMDAE. > >This just allow to not have to wait an undefined period of time > >for the DMA to be ready. > >But, on the other hand, if the time to wait the DMA is short > >enough, it should not be an issue. > In the same idea, they were other similar issues to deal with > concerning the RX and TX fifo. > > 1) Still some samples in the TX fifo when stoping/ re-starting the > TX, while RX stream is going on. > Since we can't reset the TX fifo content without disabling SSIEN, > possible samples filled by the TX DMA are still there when the TX > stream stops. And when we start it again, they introduce a random > de-synchronization of the output. > The workaround for this case was to add additional zero samples in > the fifo manually to reach a multiple of the frame size. > But I would prefer a way to empty manually the fifo instead. If > Freescale can help us to find another way as they know the internal > of the SSI... > > 2) the same for RX fifo, if the RX stream is stopped/-restarted, > while TX stream is not stopped. > We may still have some samples in the RX fifo, and those fifo must > be removed before starting the RX again. > This was more simple in this case, since we only need to read the RX > register manually until the fifo is empty, before enabling the DMA. > > Obviously, disabling the SSIEN completely to start on good basis is > not possible since we will lose a random number of samples already > present in the fifo corresponding to the stream we don't want to > stop, and this number of samples may not be a multiple of slots. You are right. Since SSI doesn't have separate FIFO reset bits for TX and RX respectively. These could be issues. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
