[alsa-devel] imx-ssi fixes

Sascha Hauer s.hauer at pengutronix.de
Thu Apr 8 17:51:13 CEST 2010

On Thu, Apr 08, 2010 at 03:47:50PM +0100, Mark Brown wrote:
> On Thu, Apr 08, 2010 at 11:31:23AM +0200, Sascha Hauer wrote:
> > Here are some bugfix patches for the imx-ssi driver. It should also fix
> > the problems reported in FIQ mode.
> Applied all three, thanks - the hrtimer stuff works an awful lot better
> than the vanilla timer stuff did.  It's a shame I hadn't noticed that
> hrtimers did manage to give better resolution on i.MX when I looked into
> this previously.
> It'd be good if you could look into the timer sync issue - doing
> something like deferring the timer by a proportion of a period if
> the period hasn't elapsed ought to cover it.

I'll look into it. I'm thinking of

- busywaiting if the current period hasn't elapsed (should rarely if
  ever the case since the fiq works reliable and the timer interrupt
  introduces additional delays.
- calculate the next callback time based on the current offset.

If you haven't pushed the patches forward it would be good to delay the
hrtimer patch a bit. I managed to shoot the system down while playing
audio with a hackbench 10. This doesn't happen without the hrtimer
patch. This may be related to the problem Valentin reported.


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