[U-Boot-Users] U-boot for Mips 4KEC

[U-Boot-Users] U-boot for Mips 4KEC

[calvin]

Hi,

In the process of porting U-boot for Malta which uses mips 4Kec I 
discovered that the stack required for intial C environment can neither 
be obtained by some on-chip memory (IMMR in MPC8xx ) nor by using DCACHE 
in locked mode. Mips 4KC has the DCache locked mode support but Mips 
4KEC has it only through external pin interface.

I am looking for a way of not using the C code till code has started 
running from RAM. But how do I get the value of gd(global data pointer) 
which U-boot expects? README file does not mention anything about mips 
registers which are specifially used for this purpose.

Thanks and Regards,
Pooja

[U-Boot-Users] U-boot for Mips 4KEC

[Wolfgang Denk]

Dear Pooja,

in message <cmajjb$oie$1@sea.gmane.org> you wrote:
> 
> In the process of porting U-boot for Malta which uses mips 4Kec I 
> discovered that the stack required for intial C environment can neither 
> be obtained by some on-chip memory (IMMR in MPC8xx ) nor by using DCACHE 
> in locked mode. Mips 4KC has the DCache locked mode support but Mips 
> 4KEC has it only through external pin interface.

I have o admit that I don't know the details of this  specirfic  CPU,
but are you _really_ sure that there is no way to lock (parts of) the
data cache? I would be relly suprised if this was the case...

> I am looking for a way of not using the C code till code has started 
> running from RAM. But how do I get the value of gd(global data pointer) 

This "way" is a major redesign and rewrite of U-Boot.

> which U-boot expects? README file does not mention anything about mips 
> registers which are specifially used for this purpose.

No matter what you do, sooner or later you will find  that  you  need
some  preliminary  stack  and  eventually  storage  space  for  a few
variables. So instead of creating several new problems,  I  recommend
to  try  to fix the root problem first, and all the rest will fall in
place.

Best regards,

Wolfgang Denk

-- 
See us @ Embedded/Electronica Munich, Nov 09 - 12, Hall A.6 Booth 513
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
An Elephant is a mouse with an Operating System.              - Knuth

[U-Boot-Users] U-boot for Mips 4KEC

[Thomas Lange]

If you look at the other MIPS boards, e.g. dbau1x00, you will
see that you setup SDRAM with assembler code to create a temporary
stack in sdram before executing any c code.
(start.S calls memsetup.S)

/Thomas

calvin wrote:
> Hi,
> 
> In the process of porting U-boot for Malta which uses mips 4Kec I 
> discovered that the stack required for intial C environment can neither 
> be obtained by some on-chip memory (IMMR in MPC8xx ) nor by using DCACHE 
> in locked mode. Mips 4KC has the DCache locked mode support but Mips 
> 4KEC has it only through external pin interface.
> 
> I am looking for a way of not using the C code till code has started 
> running from RAM. But how do I get the value of gd(global data pointer) 
> which U-boot expects? README file does not mention anything about mips 
> registers which are specifially used for this purpose.
> 
> Thanks and Regards,
> Pooja
> 
> 
> 
> 
> 
> 
> 
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