> -----Original Message----- > From: linuxppc-dev-bounces+tie-fei.zang=freescale....@lists.ozlabs.org > [mailto:linuxppc-dev-bounces+tie-fei.zang=freescale....@lists.ozlabs.org] > On Behalf Of Joakim Tjernlund > Sent: Friday, June 01, 2012 6:36 AM > To: Wood Scott-B07421 > Cc: linuxppc-...@ozlabs.org; Dan Malek; Bob Cochran; Support > Subject: Re: [RFC] [PATCH] powerpc: Add MSR_DE to MSR_KERNEL > > Scott Wood <scottw...@freescale.com> wrote on 2012/06/01 00:16:53: > > > > On 05/31/2012 05:14 PM, Joakim Tjernlund wrote: > > > Scott Wood <scottw...@freescale.com> wrote on 2012/05/31 23:43:34: > > >> > > >> On 05/31/2012 04:38 PM, Joakim Tjernlund wrote: > > >>> Scott Wood <scottw...@freescale.com> wrote on 2012/05/31 19:47:53: > > >>>> > > >>>> On 05/31/2012 04:56 AM, Joakim Tjernlund wrote: > > >>>>> Abatron Support <supp...@abatron.ch> wrote on 2012/05/31 11:30:57: > > >>>>>> > > >>>>>> > > >>>>>>> Abatron Support <supp...@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. > > >>>>> > > >>>>> Yes, that made sense to me too. How would SW debuggers work if the > kernel keeps > > >>>>> turning off MSR_DE first chance it gets? > > >>>> > > >>>> The kernel selectively enables MSR_DE when it wants to debug. I'm > not > > >>>> sure if anything will be bothered by leaving it on all the time. > This > > >>>> is something we need for virtualization as well, so a hypervisor can > > >>>> debug the guest. > > >>> > > >>> hmm, I read that as you as in favour of the patch? > > >> > > >> I'd want some confirmation that it doesn't break anything, and that > > >> there aren't any other places that need MSR_DE that this doesn't cover, > > >> but in general yes. > > > > > > Then you need to test drive the patch :) > > > > I was thinking more along the lines of someone who's more familiar with > > the relevant parts of the code confirming that it's really OK, not just > > testing that it doesn't blow up in my face. > > It just occurred to me that you guys have this already in your Linux SDK so > it can't be that bad. No. MSR_DE is ONLY added when using CW debug in SDK. Roy
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