[RFC] [PATCH] powerpc: Add MSR_DE to MSR_KERNEL

[Abatron Support]

> Abatron Support <support at abatron.ch> wrote on 2012/05/30 14:08:26:
>>
>> >> 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.

> So what is the verdict on this? I don't buy into Dan argument without some
> hard data.

What I tried to mention is that handling the MSR_DE correct is not only
an emulator (JTAG debugger) requirement. Also a software debugger may
depend on a correct handled MSR_DE bit.

Ruedi