[linux-dvb] Re: FIX: av7110 driver unusable after 'dvb-ttpci: warning: timeout waiting in BlitBitmap()'

[Oliver Endriss <o.endriss@gmx.de>]

Johannes Stezenbach wrote:
> Oliver Endriss wrote:
> > FYI, another bug has been fixed:
> > Under heavy load the bitmap transfer could be aborted by the driver due
> > to a timeout. In this case the ARM would not process OSD commands
> > anymore, and the driver must be reloaded.
> 
> Nice, but it is more a workaround than a bugfix.
> And a ten second timeout is a bit longish, don't you think?
> Anyway, the question is why the timeout happens. I'm still
> trying to figure that out.

Well, the problem is that the bandwidth for DPRAM data transfers is
limited. If you start enough simultaneous recordings with vdr, OSD
requests cannot be serviced anymore.

On the other hand, if you increase the priority of the bitmap transfers,
you would probably damage your recordings. :-(

Previously, the driver aborted the transfer after 1 second.
In this state the firmware waited for the next buffer. Forever.
(The old drivers would block forever. This is bad, since the transfer
might never complete due to heavy load.)

Now there is a timeout in the 261d firmware and a longer timeout in the
driver. Under heavy load, the request will time-out on both sides, but
the system will never run into a deadlock.

Now I can do up to 4 recordings on a FF card and still use the OSD.
It's somewhat slow but it works.

Oliver

-- 
--------------------------------------------------------
VDR Remote Plugin available at
http://www.escape-edv.de/endriss/vdr/
--------------------------------------------------------