[linux-dvb] Re: Transponder switching taking considerably longer

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Oliver Endriss wrote:
> 
> On Friday 25 July 2003 17:32, Klaus Schmidinger wrote:
> > Oliver Endriss wrote:
> > > On Friday 25 July 2003 16:44, Klaus Schmidinger wrote:
> > > > Oliver Endriss wrote:
> > > > > ...I recently changed I2C bus speed from 10.3kHz to 275kHz to
> > > > > speed up tuning and I2C firmware downloads. At least it does
> > > > > for me. ;-)
> > > > >
> > > > > Maybe this causes problems with some frontends if they need
> > > > > some delays between tuning and status check. Or they cannot
> > > > > handle the high speed reliably...
> > > > >
> > > > > Try to change
> > > > >     SAA7146_I2C_BUS_BIT_RATE_120
> > > > > back to
> > > > >     SAA7146_I2C_BUS_BIT_RATE_3200
> > > > > in saa7146_core.c. Does it make a difference?
> > > >
> > > > This results in
> > > >
> > > > Jul 25 16:41:44 video kernel: DVB: AV7111(0) - firm f0240009,
> > > > rtsl b0250018, vid 71010068, app 8000261a Jul 25 16:41:44 video
> > > > kernel: DVB: AV7111(0) - firmware supports CI link layer
> > > > interface Jul 25 16:41:45 video kernel: av7110(0): adac type set
> > > > to 0
> > > > Jul 25 16:41:45 video kernel: Couldn't read from EEPROM: not
> > > > there? ...
> > > > and the screen stays black (the OSD works, though).
> > >
> > > Argh, I think you have to increase the udelay(20) in saa7146.c line
> > > 1286 for the lower speed. Try something like udelay(500).
> >
> > With this change (in addition to the one you suggested first) it
> > works as fast as before (at least as far as I can tell, but the
> > difference was pretty obvious).
> 
> I hoped this would not happen. ;-)
> Hm, could you try to increase the speed again but set the delay to 500us
> or 1000us. I'd like to know whether it is a matter of bus speed or a
> timing issue. I think that timing problems should be fixed in the
> frontend driver. If nothing else helps we have to revert my change.

I changed saa7146_core.c back to SAA7146_I2C_BUS_BIT_RATE_120 and left
saa7146.c at udelay(500) (as in the previous test).

Switching transponders still appears to be fast, so I'd say it makes no
difference whether I use SAA7146_I2C_BUS_BIT_RATE_120 or SAA7146_I2C_BUS_BIT_RATE_3200,
as long as I have udelay(500) in saa7146.c.

Klaus


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