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To: Dan Malek <ppc6dev@digitaldans.com>
Subject: Re[2]: [RFC] [PATCH] powerpc: Add MSR_DE to MSR_KERNEL
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>> I have tested this briefly with BDI2000 on P2010(e500) and
>> it works for me. I don't know if there are any bad side effects,  
>> therfore
>> this RFC.

> We used to have MSR_DE surrounded by CONFIG_something
> to ensure it wasn't set under normal operation.  IIRC, if MSR_DE
> is set, you will have problems with software debuggers that
> utilize the the debugging registers in the chip itself.  You only want
> to force this to be set when using the BDI, not at other times.

This MSR_DE is also of interest and used for software debuggers that
make use of the debug registers. Only if MSR_DE is set then debug
interrupts are generated. If a debug event leads to a debug interrupt
handled by a software debugger or if it leads to a debug halt handled
by a JTAG tool is selected with DBCR0_EDM / DBCR0_IDM.

The "e500 Core Family Reference Manual" chapter "Chapter 8
Debug Support" explains in detail the effect of MSR_DE.

Ruedi