On Fri, 11 Aug 2006 06:42:04 +0200, Dharageswari R wrote: > > On Tue, Aug 09, 2016 at 11:54:22PM -0700, Clemens Ladisch wrote: > > Dharageswari R wrote: > > > While doing the validation of Skylake HDA driver using aplay and > > > following parameters, we noticed underrun issues. > > > > > > buffer_size : 9600 > > > period_size : 4800 > > > > > > After doing further debugging, what I found is > > > > > > 1.DMA complete interrupt occurs for the first period. > > > 2.Driver reads DMA position in buffer pointer and gets value of 4784. > > > > The interrupt says that the buffer descriptor list entry has been > > completed, but the position in buffer pointer says that the entry has > > not yet been completed. > > > yes > > > I checked with HDA architects and they are saying that when the DMA > > > completion interrupt occurs there can be slight delay before the DMA > > > Position In Buffer Pointer gets updated. > > > > The driver's interrupt handler takes care to read the interrupt status > > register first, so that any pending memory writes from the device are > > flushed. > > > > Of course, this does not work if the device posts writes _after_ the > > interrupt has been raised. This is a bug in the hardware. > > > > > So driver is expected to refill data based on whatever content is > > > reflected in the DMA Position In Buffer. > > > > No, that's not how it works. The driver waits until all 4800 frames > > are available, and the only way to wake it up is with an interrupt. > > > There is no other interrupt apart from the buffer completion interrupt > to know the post write completion. The only option here would be to > poll till the position is equal or more than the period boundary with > timeout before the period elapsed reporting. I thought of avoiding this > if possible but doesnt seem to be true. Thanks for your reply. > I will make sure that the driver reports period ellapsed > at or above the period boundary. We already have such a workaround, see bdj_pos_adj. The question is why it wasn't used or working well. (BTW your MUA seems putting strange semicolons in To and Cc entries. Better to fix it.) Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
