Am Fre, 2003-08-01 um 14.22 schrieb Dr. Werner Fink: > On Fri, Aug 01, 2003 at 01:20:21PM +0200, Oliver Endriss wrote: > > > > > > Wouldn't it be better to do the calculating instead of breaking other > > > systems which do it better _with_ a latency of 64? > >
What systems should that be? The SAA7146 needs at least 3750 ns access to the PCI-bus in one turn to deliver it's data. This is a latency of 128 on 33 MHz and 64 on 66 MHz systems. So a latency of 64 makes only sense for 66 MHz PCI-bus. Otherwise you will loose data when setting latency to 64 on a 33 MHz system. > > Sure, if someone really *knows* how to do that correctly. ;-) > > (I don't know enough about the PCI bus specs.) > > > > I considered the following: > > - DVB kernel does not set this value. > > - If required you can simply put setpci into your local boot script. > > - Many bioses allow to specify the default latency value. > > (64 seems to be a common default value.) That's for all devices on the board. But this may exceed the max. latency of a device. > > - The value 64 produces artefacts on some systems. I'm maintaining four different systems and all have artefacts with a latency of 64 but work flawless with a latency of 128 - see above for reason. > > - A built-in value makes it harder to use setpci to specify the correct And overwrites setpci in case of a driver-reload. Quite annoying if you're not in and all recordings get messed up. > > value. You have to call setpci each time after the driver has been > > loaded. > > - I'm not sure whether the DVB driver ist the correct place to do it. You're right, it's the kernel to handle the PCI-bus. > > > > Anyway, if you prefer I could make it a module parameter. > > (default is 0 --> no change, otherwise set the specified value). > > Yep ... would be perfect for me. This will help to do recording and > replaying on the same card with(out|less) glitches at least on my > 33MHz PCI system ;^) ... OK beside this a setpci command would > also help but requires lspci for getting the correct device/vendor. Put "post-install dvb-ttpci /usr/bin/setpci -d 1131:7146 latency_timer=80" into modules.conf (80 = latency of 128, 40 = 64). Maybe your problem is vice versa. If your overall-latency exceeds the max. latenty of a card sharing with your DVB-card, this may make the PCI-bus swallow and break time-shift, as data doesn't get delivered fast enough. So you don't have the problem that 128 is to much for your DVB-card, but for the overall-latency of one of your cards. You can only solve such a problem by reconfiguring your cards in the slots - but you'll need lspci for checking, of course. -- Rene Bartsch Faculties MNI Computer Science 8th Semester FH Giessen/Friedberg, Germany Facsimile/Phone: +49 7 00/72 27 87 24 Mail: [EMAIL PROTECTED] -- Info: To unsubscribe send a mail to [EMAIL PROTECTED] with "unsubscribe linux-dvb" as subject.
