After Uncompresseing Linux..., what's next

[Jim Potter]

I'm not especially familiar with the 4xx cpus, but on the 74xx cpus the MSR
register has the "privilege level" bit, which determines if the processor can
execute both user- and supervisor-level instructions, or only user-level
instructions.

This needs to be setup by the bootloader to allow supervisor-level instructions
to be executed, else you'll see some errors.


> The early code needs to perform many privileged instructions;  make sure that
> you aren't restricting the cpu to only user instructions.
>
> > I found the correct exception guys. It means
> > Privileged Instruction Exception.
> >
> > --- Prakash kanthi <pkanthi at yahoo.com> wrote:
> > >
> > > Folks,
> > >
> > > I just wanted to provide more info on my env. I have
> > > PPC405 based board with no network support forcing
> > > me
> > > to use zImage.initrd.elf.
> > >
> > > Can you suggest more on my problem described below?
> > > I
> > > saw the memory values at 0x00000000 onwards after
> > > uncompressing linux and they have changed. But when
> > > the control jumps to 0x0, my board hangs. I see that
> > > ESR is showing a value of 0x80000000, meaning either
> > > illegal instruction or Machine Check.
> > >
> > > Can you tell what's going on? What happens next
> > > after
> > > uncompressing? I am thinking it executes
> > > start_kernel
> > > function which calls lock_kernel. Let me know if i
> > > am
> > > wrong.
> > >
> > > thanks,
> > > Prakash
> > >
> > >
> > >
> > >
> > > --- James Don <JDon at spacebridge.com> wrote:
> > > > I just went thru this myself ... ;-)
> > > >
> > > > 1.) Get a BDM/JTAG tool look halt the processor
> > > > after you see " Now booting
> > > > the kernel" and look for valid asm at 0x0 ... make
> > > > sure it mathes your
> > > > start.s file ...
> > > >
> > > > 2.) Veryfy you have your mem map from ppcboot
> > > > matching requirements for the
> > > > kernel i.e ram (physical=0x0, virtual=0xc0000000)
> > > > and immr (phys 0xff000000
> > > > virtual 0xff000000) ... I had my immr in ppc boot
> > > at
> > > > 0x02200000 this screwed
> > > > me for quite a while ... otherwise you have no
> > > > printk ... the memory map is
> > > > very important not to screw with some things
> > > depend
> > > > on it (unless your
> > > > careful) ...
> > > >
> > > > 3.) verify you SMC1 (uart) is getting proper
> > > > clocking config ... i.e
> > > > bus->brg1 and brg1 is 16 times baud rate ...
> > > > otherwise you have no printk
> > > >
> > > > 4.) and always always keep in mind your RAM refesh
> > > > could be wrong ...
> > > > everyone will tell you this even when it has
> > > nothing
> > > > to do with your problem
> > > > ... try not to ignore them if you are still stuck
> > > > ;-) But verifying step 1
> > > > should prove your ok ...
> > > >
> > > > Best of luck,
> > > > Jim
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: Prakash kanthi [mailto:pkanthi at yahoo.com]
> > > > Sent: Wednesday, December 18, 2002 7:14 PM
> > > > To: LinuxPPC
> > > > Subject: After Uncompresseing Linux..., what's
> > > next
> > > >
> > > >
> > > > Hi there,
> > > >
> > > > I was trying to load linuxppc_2_4_devel onto my
> > > > board.
> > > > It goes through the board info read, UART init and
> > > > Uncompressing the linux kernel. But after that, i
> > > do
> > > > not see any messages and board hangs.
> > > >
> > > > Here is the UART output:
> > > > ------------------------------------
> > > > OS Booting...
> > > >
> > > > loaded at:     00400000 0060D1CC
> > > > board data at: 00000030 00000044
> > > > relocated to:  00405C24 00405C38
> > > > zimage at:     00406290 004A08FF
> > > > initrd at:     004A1000 006097CA
> > > > avail ram:     0060E000 007F8000
> > > >
> > > > Linux/PPC load: console=ttyS0,9600 console=tty1
> > > > ip=on
> > > > root=/dev/xsysace/disc0/pa
> > > > rt3 rw
> > > > Uncompressing Linux...done.
> > > > Now booting the kernel
> > > > -------------------------------------------
> > > >
> > > > After the last line, it hangs. I get a feeling
> > > that,
> > > > the uncompressing process is not writing in the
> > > > memory
> > > > starting from 0x00000000 and, after uncompressing,
> > > > it
> > > > is jumping into 0x00000000 and is not able to find
> > > > anything.
> > > >
> > > > My questions are,
> > > > 1. How can i make sure that, the uncompressing
> > > > process
> > > > is going to start writing the data from
> > > 0x00000000.
> > > >
> > > > 2. How big a space this uncompressing process
> > > needs?
> > > > And also how much overall memory is required for
> > > > running linux. I just have 8MB SDRAM.
> > > >
> > > > 3. What is the next step in the booting process?
> > > > Which
> > > > Device (eth, pci, ide, ???) Initialization?
> > > >
> > > > Your help is appreciated.
> > > >
> > > > thanks,
> > > > Prakash
> > > >
> > > >
> > >
> > >
> > >
> >
>
> --
> Sincerely,
>
> Jim Potter
> 45th Parallel Processing
>
>   Firefighting: Bustin' ours, Savin' yours.
>

--
Sincerely,

Jim Potter
45th Parallel Processing

  Firefighting: Bustin' ours, Savin' yours.


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