On Friday 31 May 2002 2:00 pm, Keith Whitwell scribed numinously:" > Tim Smith wrote: > > I conclude from this that writing the ring tail register causes the > > card to fetch all the commands up until that point and feed them to its > > FIFO, which may fill it... It's certainly possible for the FIFO to go > > from 64 slots free to 0 in one ioctl... > > I can't believe this. The ring is there specifically so that you don't > have to worry about the fifo. It's a big buffer between you & the > hardware - the hardware drains the ring at it's pace & you fill it at > yours. > > Also note that you can tell the ring to fire off a big (64k or more) > buffer of commands sitting elsewhere in agp space. That might be tens of > thousands of fifo slots for a single write to the ring tail register.
I was being unclear. What I mean is that you can fire off a big chunk of commands via (e.g.) radeon_cp_cmdbuf, and when you COMMIT_RING() the FIFO is empty (64 slots free), but a few microseconds later when you com back to do your do_cp_idle(), the card has fetched a load of stuff to work on and the FIFO is full. This is obviously true and I don't expect it to be news :-) I seem to be observing the behaviour that if, on entry to do_cp_idle() the FIFO is not empty already, it never will be empty and the whole thing goes pear shaped. Thus, if a big collection of commands is just followed by more commands this doesn't seem to cause a problem, but if a big collection of commands is followed very quickly by a cp_idle(), it goes funny. This may of course be Yet Another Symptom, of which I seem to have chased many :-) > I'm still scratching my head... Me too. Could this be a locking problem? There seem to be two contexts owned by the same PID in this case, and the LOCK_TEST_WITH_RETURN() macro only tests that the PID is the same as the currently holding PID, not the context. -- Tim Smith ([EMAIL PROTECTED]) Trust the sysadmin. The sysadmin is your friend. The sysadmin wants you to be happy. If you are not happy, you may be used as reactor shielding. _______________________________________________________________ Don't miss the 2002 Sprint PCS Application Developer's Conference August 25-28 in Las Vegas -- http://devcon.sprintpcs.com/adp/index.cfm _______________________________________________ Dri-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/dri-devel
