On Fri, Oct 22, 2010 at 8:22 AM, Marek Vasut [off-list ref] wrote:

Dne Po 18. ??jna 2010 19:38:49 Michael Cashwell napsal(a):

quoted

Greetings,

I've been fighting inexplicable hangs on two different PXA270 designs
running various kernels since early 2.6.28.x. The first board was custom
(and of dubious integrity) but I'm currently seeing it on Gumstix Verdex
PROs running 2.6.35.7.

At first I thought it was a problem with CPU-freq code itself hitting some
unaddressed errata but I've eliminated that possibility. The hangs occur
even if CPU-freq is disabled in the kernel config. All that's required in
that case is for u-boot to run the kernel at a core frequency of 312MHz or
lower. If it runs at 416MHz or higher no hangs occur. (With CPU-freq
enabled the hangs only occur if speeds at or below 312MHz are allowed.
With those commented out, no hangs.)

At low core frequencies I can trigger the hang every time by copying a
several-MB file to a uSD card via the MMC interface. The copy command
completes but a few seconds later (while the background processes write to
the card) the CPU hangs.** However, the issue is not specific to uSD/MMC.
Another developer told me he has seen hangs while receiving data through a
UART connected via I2C.

The hangs are hard (rendering JTAG inoperable) and since I have no hardware
with the Embedded Trace Module exposed I have no way to gather a trace of
execution up to the freeze.

I'd like to solve the problem since the lower speeds are more power
efficient but I'm somewhat stuck regarding how to debug it. I'd like to
know if it's something I'm doing wrong so my first step is to ask the
ARM-Linux community if anyone else has run recent kernels on a PXA270
system at core clock rates of 312MHz or less. (That's also a not so veiled
plea for someone to perhaps do so if they have the hardware and a few
spare cycles.)

Could it be memory-related ? Like, RAM crashes because of refresh speed or
something?

Cheers

quoted

Thanks for any information.
-Mike

**: Here's a hang where I'd just started top while background threads were
writing to the uSD card. top did its first pass and then everything froze.
(Is the high rate of context switches and interrupts normal?)

last pid: ? 389; ?load avg: ?0.13, ?0.05, ?0.01; ?up 0+00:28:15
12:40:22 27 processes: 1 running, 24 sleeping, 2 uninterruptable
CPU states: ?0.0% user, ?0.0% nice, 31.1% system, 13.6% idle, 55.3% iowait
Kernel: 30832 ctxsw, 16262 intr
Memory: 32M used, 92M free, 244K buffers, 27M cached
Swap:
?This terminal can only display 16 processes
? PID USERNAME ?THR PRI NICE ?SIZE ? RES ? SHR STATE ? TIME ? ?CPU COMMAND
? 236 root ? ? ? ?1 ?20 ? ?0 ? ?0K ? ?0K ? ?0K disk ? ?0:00 28.43% mmcqd
? 389 root ? ? ? ?1 ?20 ? ?0 2696K ?804K ?648K run ? ? 0:00 ?3.92% top
? 378 root ? ? ? ?1 ?20 ? ?0 ? ?0K ? ?0K ? ?0K disk ? ?0:00 ?1.96%
flush-179:0 1 root ? ? ? ?1 ?20 ? ?0 2784K ?672K ?588K sleep ? 0:00 ?0.00%
init 119 root ? ? ? ?1 ?20 ? ?0 ? ?0K ? ?0K ? ?0K sleep ? 0:00 ?0.00%
rpciod/0 371 root ? ? ? ?1 ?20 ? ?0 4208K 1592K 1340K sleep ? 0:00 ?0.00%
sshd 369 root ? ? ? ?1 ?20 ? ?0 2788K ?716K ?632K sleep ? 0:00 ?0.00% ash
4 root ? ? ? ?1 ?20 ? ?0 ? ?0K ? ?0K ? ?0K sleep ? 0:00 ?0.00% events/0
128 root ? ? ? ?1 ?20 ? ?0 ? ?0K ? ?0K ? ?0K sleep ? 0:00 ?0.00% nfsiod
251 root ? ? ? ?1 ?20 ? ?0 2784K ?460K ?380K sleep ? 0:00 ?0.00% klogd 249
root ? ? ? ?1 ?20 ? ?0 2784K ?464K ?396K sleep ? 0:00 ?0.00% syslogd 5
root ? ? ? ?1 ?20 ? ?0 ? ?0K ? ?0K ? ?0K sleep ? 0:00 ?0.00% khelper 370
root ? ? ? ?1 ?20 ? ?0 2784K ?440K ?376K sleep ? 0:00 ?0.00% busybox 103
root ? ? ? ?1 ?20 ? ?0 ? ?0K ? ?0K ? ?0K sleep ? 0:00 ?0.00% kmmcd 2 root
? ? ? 1 ?20 ? ?0 ? ?0K ? ?0K ? ?0K sleep ? 0:00 ?0.00% kthreadd 3 root
? ?1 ?20 ? ?0 ? ?0K ? ?0K ? ?0K sleep ? 0:00 ?0.00% ksoftirqd/0

Suggest to check errata first. Maybe we need some special code sequence.