At Fri, 25 Jan 2008 17:07:27 +0100, Hermann Lauer wrote: > > On Fri, Jan 25, 2008 at 11:44:12AM +0100, Takashi Iwai wrote: > > > > Then a question arises - why DMAADDR isn't used as the primary source > > > > at all? Is it less stable than DMACOUNT in some cases? > > > > > > I don't know and the current implementation contains only a "don't ask why - AB" > > > comment. > > > > > > To reiterate: My proposed patch is about minimising the chance that a > > > wrong hw pointer value is given back due to garbage read from the chip. If > > > you are interested, I can send you debugging output which shows > > > that both DMAADDR and DMACOUNT are read out as bogus values > > > from time to time - one or the another, or both. I tried some > > > status flags on the chip, but alway found cases where it's > > > not clear if and which one of the two is correct. > > > > Yeah, it would be helpful to understand the problem more correctly. > > Will put together some of the log files next week. > Up to what size could/should I cc to the list without upsetting people ? > I guess compressing them will yield only a few KBytes. Not sure about the size limit, but it'd be better to attach a compressed file. Or just cut out only the interesting part. > > > That can play a role with the handling of the off-by-one bug of the chip. > > > > What is the problem exactly? > > If I interpreted my tests output correctly, the last byte of a period > is written by the DMA engine after the interrupt occurs. So the > hw pointer probably has to be decremented by one and is then > pointing to the last frame (Or even that before: Has the hw pointer to point > at the frame which is written at the moment or the one which is > guaranteed to be written completely by the hardware ?) This sounds a bit odd. Isn't it rather the setup of the hardware parameter wrong? I mean, the count calculation in *_prepare() can be the size - 1? Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
