From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <003201bf82be$25a8a670$0a01010a@gamma> From: "Damjan Lampret" To: "Dan Malek" Cc: References: <002601bf81dc$184f9480$0a01010a@gamma> <38B9E821.1E486142@netx4.com> Subject: Re: Data TLB error exception Date: Tue, 29 Feb 2000 15:06:16 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: > Damjan Lampret wrote: > > > I am playing with 2.2.13 kernel on custom MPC860 board and I have a problem > > with DTLB error (1400h) exception. I downloaded my kernel via BDM and it > > BDMs with MMU and caches are a bad combination. With the exception of > KGDB, there are no debuggers that understand the Linux kernel once > the MMU is enabled. The debugger tools normally used with BDMs trap > MMU exceptions as a "bad thing" or at least try to invoke some monitor > support code that is supposed to reside in the kernel. > I use EST's VisionICE. I use it to download code and to check which exceptions occur. Of course I also assumed that debugger is having problems with exceptions so I disabled detection in DER but my target still hangs. I am quite sure that visionICE is not executing any "monitor support" code. Like most debuggers it does not support MMU so I need to add 0xc0000000 to all addresses when analyzing kernel code. > The MMUs and caches work fine on the 8xx processors when running Linux/PPC. > I have been running them all day, every day, for years and have several > products deployed in the field without trouble. > Yes, apparently there is a problem running target with BDM and caches enabled. As I said in my original email when I disabled caches target is much more stable (but still hangs after a couple of minutes). Perhaps this is still because of a debugger. Although I don't understand how a debugger can harm target when target is not in debug mode (when running "real-time"). > If you are using BDMs for downloading Linux, that is all you can do with > them. Once the kernel executes the first few lines of code to enable I do use it for downloading code. > the MMU, you are done. If you can't disable _all_ debugging from the > BDM tool, including show cycles, you can't use it with Linux. > You can disable and I did. Target still hangs. What I don't understand is why after DTLB error exception. Everytime I get machine check in data access exception handler. I'll backtrace it and post my results to the list. regards, Damjan ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/