Re: JTAG debugging of the kernel

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Peter Barada wrote:
On Fri, 2008-08-15 at 23:04 +0530, Syed Mohammed, Khasim wrote:
-----Original Message-----
From: linux-omap-owner@xxxxxxxxxxxxxxx [mailto:linux-omap-owner@xxxxxxxxxxxxxxx] On Behalf Of Peter
Barada

Any suggestions on what can cause the JTAG to stop working after the
kernel starts?

I think you should disable Power Management. Which kernel are you using now?

2.6.22.18.  I'm planning to move to 2.6.26 after the dust settles...

I'll try w/o power management, but any idea why power management might
affect JTAG?

The guy I share an office with (who's out on vacation) worked through this with their tech support, who suggested replacing WFI instructions with NOPs.

Look at cpu_v7_do_idle in arch/arm/mm/proc-v7.S. Changing the WFI to a NOP did the trick for him.

Presumably power management was off, but even WFI (wait for interrupt) put the CPU in a state that wasn't handled by the BDI firmware at the time. I'm not sure if they resolved the issue in a later firmware update or not. We didn't think the workaround was worthy of a Kconfig option - hopefully updated firmware for the BDI box will address the issue.


- Josh
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