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<TITLE>kernel access of bad area, sig: 11 ( mpc852t)</TITLE>
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<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New"> Hi,</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New"> Im having problem porting linux kernel 2.4.21 to our mpc852T custom</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New"> board.The kernel</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New"> panics randomly with sig 11.</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New"> The board boots up fine and we also get to the prompt.When we open 3-4</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New"> telnet sessions</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New"> and try to run some command the kernel panics.This is completely</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New"> random.Sometimes it</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New"> even panics before opening the telnet session.</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">>>></FONT></SPAN></P>
<BR>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">>>> <oops dump snipped></FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">>>></FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New">You almost certainly have SDRAM problems. If you have thoroughly checked</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New">out the</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New">complete address range statically, remember that burst accesses will not</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New">occur until the</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New">cache is turned on, so your problem may be with bursting. But you can also</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New">have severe</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New">problems like a missing address line and linux still run for a few seconds.</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>></FONT></SPAN><SPAN LANG="en-us"><I></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>></FONT></SPAN><SPAN LANG="en-us"><I><FONT SIZE=2 FACE="Courier New">Mark Chambers</FONT></I></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>We've checked the SDRAM. The timings (UPM) look fine. The problem</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>however is that linux does not hang until after a few processes are</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>started.</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>If we boot to linux and leave it as it is, everything is fine and the</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>board remains working. However each time a few processes (4-5 telnet</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>sessions for eg.) are started the system either panics or hangs (goes</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>dead).</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>Thanks in advance,</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Courier New">>Akshay</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">We have been experiencing this same issue with random boards in production. The exact same version of software will run for months on other instances of the exact same board design, but a few percent get ‘random’ trap 300s. When they do occur, it’s only after Linux has booted and address translation and caching are turned on. Examining the oops-es and memory shows that some location in SDRAM has a bogus value, but I don’t have the tools to trace back how it got that way.</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">I have ported a rigorous moving-inversions memory test into our firmware, and have run it extensively across the entire SDRAM address space (the test code executes from flash). I have let this test run continuously for hours and hours, but never found a memory problem. Unfortunately, I do not have test software that enables the MMU address translation or caching, so as Mark said, I can’t test memory using bursting. Our hardware engineers have reviewed the designs very carefully and are quite confident that there is plenty of margin in the memory timing. Signal quality has also been carefully checked.</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">Our manufacturing people have replaced the CPU on some of these boards, and the problem went away.</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">If anyone else on the mailing list has experienced this issue, or has developed a virtual address memory test, please let us know.</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial">Ken Poole</FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"> </FONT></SPAN></P>
<P ALIGN=LEFT><SPAN LANG="en-us"><FONT SIZE=2 FACE="Arial"></FONT></SPAN><SPAN LANG="en-us"></SPAN><SPAN LANG="en-us"> </SPAN></P>
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