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From: Zang Roy-R61911 <r61911@freescale.com>
To: Joakim Tjernlund <joakim.tjernlund@transmode.se>,
	Wood Scott-B07421 <B07421@freescale.com>
Cc: "linuxppc-dev@ozlabs.org" <linuxppc-dev@ozlabs.org>,
	Dan Malek <ppc6dev@digitaldans.com>,
	Bob Cochran <ppc@mindchasers.com>, Support <support@abatron.ch>
Subject: RE: [RFC] [PATCH] powerpc: Add MSR_DE to MSR_KERNEL
Date: Fri, 20 Jul 2012 08:27:52 +0000	[thread overview]
Message-ID: <3E027F8168735B46AC006B1D0C7BB002079C3290@039-SN2MPN1-013.039d.mgd.msft.net> (raw)
In-Reply-To: <OFDC3DAEDA.27E0B532-ONC1257A0F.007BF637-C1257A0F.007C1E26@transmode.se>



> -----Original Message-----
> From: linuxppc-dev-bounces+tie-fei.zang=3Dfreescale.com@lists.ozlabs.org
> [mailto:linuxppc-dev-bounces+tie-fei.zang=3Dfreescale.com@lists.ozlabs.or=
g]
> On Behalf Of Joakim Tjernlund
> Sent: Friday, June 01, 2012 6:36 AM
> To: Wood Scott-B07421
> Cc: linuxppc-dev@ozlabs.org; Dan Malek; Bob Cochran; Support
> Subject: Re: [RFC] [PATCH] powerpc: Add MSR_DE to MSR_KERNEL
>=20
> Scott Wood <scottwood@freescale.com> wrote on 2012/06/01 00:16:53:
> >
> > On 05/31/2012 05:14 PM, Joakim Tjernlund wrote:
> > > Scott Wood <scottwood@freescale.com> wrote on 2012/05/31 23:43:34:
> > >>
> > >> On 05/31/2012 04:38 PM, Joakim Tjernlund wrote:
> > >>> Scott Wood <scottwood@freescale.com> wrote on 2012/05/31 19:47:53:
> > >>>>
> > >>>> On 05/31/2012 04:56 AM, Joakim Tjernlund wrote:
> > >>>>> Abatron Support <support@abatron.ch> wrote on 2012/05/31 11:30:57=
:
> > >>>>>>
> > >>>>>>
> > >>>>>>> Abatron Support <support@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 time=
s.
> > >>>>>>>>
> > >>>>>>>> This MSR_DE is also of interest and used for software debugger=
s
> 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 n=
ot
> only
> > >>>>>> an emulator (JTAG debugger) requirement. Also a software debugge=
r
> may
> > >>>>>> depend on a correct handled MSR_DE bit.
> > >>>>>
> > >>>>> Yes, that made sense to me too. How would SW debuggers work if th=
e
> 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 c=
an
> > >>>> 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 cov=
er,
> > >> 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.
>=20
> 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

  reply	other threads:[~2012-07-20  8:28 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-30  7:43 [RFC] [PATCH] powerpc: Add MSR_DE to MSR_KERNEL Joakim Tjernlund
2012-05-30  7:59 ` Dan Malek
2012-05-30 12:08   ` Re[2]: " Abatron Support
2012-05-31  9:05     ` Joakim Tjernlund
2012-05-31  9:30       ` Re[4]: " Abatron Support
2012-05-31  9:56         ` Joakim Tjernlund
2012-05-31 17:47           ` Scott Wood
2012-05-31 21:38             ` Joakim Tjernlund
2012-05-31 21:43               ` Scott Wood
2012-05-31 22:14                 ` Joakim Tjernlund
2012-05-31 22:16                   ` Scott Wood
2012-05-31 22:33                     ` Joakim Tjernlund
2012-05-31 22:35                     ` Joakim Tjernlund
2012-07-20  8:27                       ` Zang Roy-R61911 [this message]
2012-07-20  8:37                         ` Joakim Tjernlund
2013-06-25  0:51                           ` Scott Wood
2013-06-25  6:00                             ` Joakim Tjernlund
2013-06-26 21:42                               ` Scott Wood
2012-06-01  9:12       ` Re[2]: " Benjamin Herrenschmidt
2012-06-01 10:34         ` Joakim Tjernlund
2012-05-30 13:26 ` Bob Cochran
2012-06-01  9:14   ` Benjamin Herrenschmidt
2012-06-01 10:38     ` Joakim Tjernlund
2012-06-01 16:28     ` Scott Wood
2012-06-01 22:30       ` Benjamin Herrenschmidt
2012-06-01 22:42         ` Scott Wood
2012-06-01 23:24           ` Benjamin Herrenschmidt
2012-06-02 18:29             ` Joakim Tjernlund
2012-06-02 21:21               ` Benjamin Herrenschmidt
2012-06-03  9:20                 ` Joakim Tjernlund
2012-06-04  9:06                 ` Joakim Tjernlund
     [not found]                 ` <OF7810EBD9.B191A242-ONC1257A13.0031E9E3-C1257A13.00320D10@LocalDomain>
2012-07-11 14:24                   ` Joakim Tjernlund
2012-07-11 14:45                     ` Kumar Gala

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