MPC85xx PCI transfer disconnect

Liu Dave-r63238 DaveLiu at freescale.com
Mon Jun 5 20:33:45 EST 2006


 
> After scaning more logic analyzer captures, I noticed that 
> occasionally the MPC85xx inserts additional wait states (by 
> deasserting TRDY#) after only 32 bytes have been transferred. 
>  So it definitely appears that (the way I have things 
> configured now) there's a 20-80ns delay after 1 cache line is 
> read, and the MPC85xx disconnects transfers that are larger 
> than 2 cache lines.
> 

There is one description about MRM cmd in the MPC85xx user manual.
[Memory read multiple] 
Similar to the memory-read command, but also causes a
prefetch of the next cache line (32 bytes).

How many masters in your PCI system? 
Maybe, you can tune the master latency timer of Tsi148 to get more bandwidth.
The latecy timer is locate at configuration space of your master.

Dave



More information about the Linuxppc-embedded mailing list