CONFIG_SERIAL_TEXT_DEBUG causes exception

[Gary D. Thomas]

On Wed, 2003-03-19 at 20:05, jwalden at digitalatlantic.com wrote:
>
> Thanks for the info -
>
> It doesn't look to me like the 4xx has a BAT -
> what would I use instead?
>

One way would be to use a locked TLB.  I'm sure there are others.

> Jerry Walden
>
> -----Original Message-----
> From: Gary D. Thomas [mailto:gary.thomas at mind.be]
> Sent: Wednesday, March 19, 2003 4:19 PM
> To: Jerry Walden
> Cc: linuxppc embedded
> Subject: RE: CONFIG_SERIAL_TEXT_DEBUG causes exception
>
>
> On Wed, 2003-03-19 at 14:04, Jerry Walden wrote:
> > What other embedded board (hopefully a ppc) would you suggest -
> > I don't see any special provisions in the kernel for a custom
> > mapping of these registers based on a configuration option for any
> > specific board - this appears to be generic code that meant for
> > all platforms - I believe what you say regarding what I have to
> > do:
> >
> > 1) I can't find sample code that you refer to.
> > 2) I am confused as to why this code is in the kernel in the way it is
> >    because it seems to me that most embedded processors have an MMU,
> >    so why the comment in that section of code that says "assuming the
> >    firmware setup the board properly...."
> >
>
> As soon as the kernel starts, there are *no* mappings, other than
> RAM, unless explicitly set up.
>
> Try looking at arch/ppc/platforms/pumaA.c (in the 2_4_devel kernel).
> This explicit mapping  happens in the "platform_init" function,
> near the end.
>
> n.b. it's polite to copy such dialogue to the mailing list so that
> everyone else can benefit.  If you want (or need) private help, you
> can arrange for it.
>
> > Thanks Much for Your Help
> >
> > Jerry Walden
> >
> > -----Original Message-----
> > From: owner-linuxppc-embedded at lists.linuxppc.org
> > [mailto:owner-linuxppc-embedded at lists.linuxppc.org]On Behalf Of Gary D.
> > Thomas
> > Sent: Wednesday, March 19, 2003 12:54 PM
> > To: jwalden at digitalatlantic.com
> > Cc: linuxppc embedded
> > Subject: Re: CONFIG_SERIAL_TEXT_DEBUG causes exception
> >
> >
> >
> > On Wed, 2003-03-19 at 10:47, Jerry Walden wrote:
> > >
> > > Hello:
> > >
> > > I have a custom PPC405GPr board that I have successfully ported u-boot to.
> > >
> > > I am now at the stage of trying to bring Linux up on the board.
> > >
> > > I have CONFIG_SERIAL_TEXT_DEBUG defined for the kernel that I am trying to
> > > bring up.  I would like to have this option so I can trace through the
> > > kernel.
> > > The comments in ppc4xx_setup.c in the function serial_putc indicate that
> > as
> > > long
> > > as the firmware (in my case u-boot) has been initialized properly, then
> > this
> > > function
> > > should work.  I have verified the addresses that the function is trying to
> > > write to
> > > and they are correct.  However, when serial_putc calls the first readb, I
> > > get an
> > > exception.
> > >
> > > Can someone please provide some pointers as to what might be wrong?
> >
> > You need to make sure that the serial registers are mapped at
> > that point.  I don't know the details of your U-boot implementation,
> > but the kernel will most certainly not have this region mapped
> > unless you make it happen explicitly.  Look at some other embedded
> > boards and you'll find code to set this up, typically using a BAT or
> > some other special mapping.
> >
> > --
> > .--------------------------------------------------------.
> > |       Mind: Embedded Linux and eCos Development        |
> > |--------------------------------------------------------|
> > | Gary Thomas              email:  gary.thomas at mind.be   |
> > | Mind ( http://mind.be )  tel:    +1 (970) 229-1963     |
> > | gpg: http://www.chez-thomas.org/gary/gpg_key.asc       |
> > '--------------------------------------------------------'
> >
> >
> >
> --
> --------------------------------------------------------.
> |       Mind: Embedded Linux and eCos Development        |
> |--------------------------------------------------------|
> | Gary Thomas              email:  gary.thomas at mind.be   |
> | Mind ( http://mind.be )  tel:    +1 (970) 229-1963     |
> | gpg: http://www.chez-thomas.org/gary/gpg_key.asc       |
> '--------------------------------------------------------'
>
--
.--------------------------------------------------------.
|       Mind: Embedded Linux and eCos Development        |
|--------------------------------------------------------|
| Gary Thomas              email:  gary.thomas at mind.be   |
| Mind ( http://mind.be )  tel:    +1 (970) 229-1963     |
| gpg: http://www.chez-thomas.org/gary/gpg_key.asc       |
'--------------------------------------------------------'


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