MPC8260 + L2 Cache: ever been done?
wd at denx.de
Tue Apr 23 07:34:53 EST 2002
in message <188.8.131.52.2.20020422102923.00af7550 at carts.com> you wrote:
> Has anyone ever seen an MPC8260-based design with L2
> cache run Linux (or any OS) with some semblance of stability?
Ummm.... you should improve your internal communication: Kevin Fry
<kevin at carts.com> has asked the same question just 2 days ago, and I
Yes, for example the TQM8260 modules come in some configurations with
L2 cache. It's a shipping product which runs 100% stable.
> I know there are several designs out there with an 8260 and
> L2, but they usually also have a 750 or some other CPU, and
> the L2 is hooked up to that CPU, not the 8260. I've checked the
> archives and searched online, but have been unable to find
> any information on these two devices working together.
It's working here.
> We have an 8260 design running in 60X-compatible mode with
> 1 to 4 MPC2605 L2 cache devices, and cache size is jumper-
There is only 1 x MPC2605 om the TQM8260 modules.
> selectable. Also on the 60X bus are a DIMM and a 16-bit flash.
> When L2 is turned off, Linux runs fine (we're using 2.4.18).
> When 256kB of L2 is enabled, Linux boots partially and then
> crashes, either freezing or getting infinite machine checks.
> When 512kB or 1MB are enabled, I never see any output from
> Linux. We're using PPCBoot 1.1.2 for booting, and the L2 is
> turned on in Linux (arch/ppc/kernel/head.S).
Never tried it with more than 256kB of L2; but you can check out and
compare with the TQM8260_L2 resp. TQM8260_L2_266MHz configurations in
> location in memory in an infinite loop. It is not doing instruction
> fetches and accessing data from all over memory like Linux does.
Are you really sure it's a cache issue? So far I have seen many more
cases where the real cause of the problem was improper SDRAM
operation (failing in burst mode).
> init code for the L2 that Motorola provided us in head.S) The
> difficult part about debugging this problem is that Linux crashes
> in different ways at different times, so I've been unable to trigger
That just means you have a memory problem, which _can_ be cache
> Some other info: We've tried running the system in write-through
> mode with the same results. We've done this test with two
> versions of the 8260, mask A.1 and the new HiP4 (2k25a). And
> the CPM fifos are all either in local bus RAM or DPRAM in order
> to keep the CPM off the 60X bus (which causes other problems).
It works here for C.2 [6K23A] and A.0(A) [2K25A]; on the TQM8260 we
cannot enable L2 on the A.0 [K22A] because the CPM (running at 133
MHz) has DMA problems there, and we cannot easily reduce the CPM
speed to <100MHz on this board.
> If anyone has any answers, ideas, or insights into this problem,
> they'd be greatly appreciated.
All I can say is: it works for us on the only board that I have with
L2 cache on it...
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd at denx.de
Lack of skill dictates economy of style. - Joey Ramone
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