Access to registers of MPC823E

Access to registers of MPC823E

[David de Andrés Martínez]

Hello,

I'm trying to write a program to run in Linux 2.4.4 (booting from
PPCBoot) on a TQM823L (MPC823E), but I'm having some problems.

I have the following definitions in the headers:
----------------
#define TCGR IMR_USHORT(0x0980)
#define IMR_USHORT(addr) V_USHORT(CFG_IMMR + addr)
#define IMR_USHORT(addr) (addr)
#define V_USHORT(a) (*(volatile unsigned short *)(a))
#define CFG_IMMR 0xFFF00000
----------------

When my main program tries to access to TCGR to read or write it simply
exits out of the program without a warning into the shell.
----------
> ./main
> START....
>
----------

Just to check if something is wrong, I have tested this code:
-----------------
 unsigned long immr;

 asm( "mfspr %0,638": "=r"(immr) : );
 printf("IMMR = %li\n", immr);
----------------

But it didn't printf anything, just gets out of the program as before.

Got any idea of what can be going on?

--
----------------------------------------------------------------------
| David de Andrés Martínez   | Fault Tolerant Systems research Group |
|                            |                                       |
| Computer Science Engineer  | Email: ddandres@disca.upv.es          |
| Doctorate Student          | Phone: +34 96 387.75.74 Ext 75774     |
|                            | Fax: +34 96 387.75.79                 |
-------Address--------------------------------------------------------
|                 DISCA-EUI                                          |
|                 Universidad Politécnica de Valencia                |
|                 Campus de Vera #14                                 |
|                 Valencia E-46021                                   |
|                 Spain                                              |
----------------------------------------------------------------------

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

Re: Access to registers of MPC823E

[Wolfgang Denk]

In message <3BCD5B30.5396ADEC@disca.upv.es> you wrote:
>
> I'm trying to write a program to run in Linux 2.4.4 (booting from
> PPCBoot) on a TQM823L (MPC823E), but I'm having some problems.
...
> #define CFG_IMMR 0xFFF00000
...
> When my main program tries to access to TCGR to read or write it simply
> exits out of the program without a warning into the shell.
...
>  asm( "mfspr %0,638": "=r"(immr) : );
>  printf("IMMR = %li\n", immr);
...
> Got any idea of what can be going on?

In user space you cannot  access  hardware  directly  using  physical
addresses, nor execute any priviledged istructions.

The Linux kernel protects itself from  malicious  users  who  try  to
tamper with it's internals :-)

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
The Gates in my computer are AND, OR and NOT; they are not Bill.

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/