[U-Boot-Users] ARM946, u-boot and linux

[U-Boot-Users] ARM946, u-boot and linux

[Shawn Jin]

Hi,

My next project will be on ARM946, a microprocessor without MMU. I'm
totally a newbie to ARM processors though have experiences on porting
u-boot and linux to several ppc processors. I am studying on how to
set up the cross development environment. Please shed some light on
these questions haunting me recently.

1. uclinux or linux?
Since ARM946 has no MMU, uclinux might be a better starting point for
porting linux to ARM946. But I have to find out the relationship
between uclinux and linux. To my understanding, uclinux must be a
patch to the normal linux distribution.

2. Boot loader?
Does u-boot support ARM946? I know u-boot supports some ARM processors
with MMU, such as 926. Or more general question: does u-boot support
processors without MMU? From my ppc experience I know MMU is enabled
on u-boot.

3. cross tool chain?
Does ELDK support ARM946? ELDK supports arm920. ELDK can be used for
arm946 if its core is compatible with arm920's. If ELDK doesn't
support it, does it mean that I have to build the cross tool chain
from scratch? Is there any off-shelf tool I can use? I tried to build
ppc cross tool chain from scratch before the crosstool came into
being. That's not a straightforward step, actually painful.

Thank you very much!

-Shawn.

[U-Boot-Users] ARM946, u-boot and linux

[Wolfgang Denk]

Dear Shawn,

in message <c3d0340b04072711035f9822df@mail.gmail.com> you wrote:
> 
> 1. uclinux or linux?

strictly speaking: this question is off topic on this mailing list.

> Since ARM946 has no MMU, uclinux might be a better starting point for
> porting linux to ARM946. But I have to find out the relationship

Let's rephrase it: the only chance you have on a MMU-less  system  is
by using uCLinux. For standard Linux a working MMU is mandatory.

Note that it seens that  uCLinux  has  already  been  ported  to  the
ARM946.

> between uclinux and linux. To my understanding, uclinux must be a
> patch to the normal linux distribution.

Not really. It's actually more of a different implemenation.  And  in
2.6 it's being merged into the standard kernel tree.

> 2. Boot loader?
> Does u-boot support ARM946? I know u-boot supports some ARM processors

Not yet, but it should be straightforward to add.

> with MMU, such as 926. Or more general question: does u-boot support
> processors without MMU? From my ppc experience I know MMU is enabled
> on u-boot.

Yes, U-Boot does support MMU-less systems (see for  example  all  the
ARM7 or StrongARM systems, or the MIPS "purple" configuration).

And you are wrong: U-Boot does NOT use the MMU on PPC. [At least  not
on  all  processors,  and  if then not for virtual memory but just to
play dirt^H^H^H^Hclever tricks with the data cache.]

> Does ELDK support ARM946? ELDK supports arm920. ELDK can be used for
> arm946 if its core is compatible with arm920's. If ELDK doesn't

You can use the cross toolchain, but the ative target tools  will  of
course not run as they require a standard Linux kernel, not uCLinux.

> support it, does it mean that I have to build the cross tool chain
> from scratch? Is there any off-shelf tool I can use? I tried to build

There are many. Did you attempt to search the Web?

> ppc cross tool chain from scratch before the crosstool came into
> being. That's not a straightforward step, actually painful.

Painful it is, indeed. 

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
The human race is faced with a cruel choice: work  or  daytime  tele-
vision.

[U-Boot-Users] ARM946, u-boot and linux

[Shawn Jin]

Dear Wolfgang,

On Wed, 28 Jul 2004 00:00:27 +0200, Wolfgang Denk <wd@denx.de> wrote:
> > 1. uclinux or linux?
>
> Let's rephrase it: the only chance you have on a MMU-less  system  is
> by using uCLinux. For standard Linux a working MMU is mandatory.
> 
> Note that it seens that  uCLinux  has  already  been  ported  to  the
> ARM946.

Thanks. Now I know what I need to focus.
 
> > 2. Boot loader?
> > with MMU, such as 926. Or more general question: does u-boot support
> > processors without MMU? From my ppc experience I know MMU is enabled
> > on u-boot.
> 
> And you are wrong: U-Boot does NOT use the MMU on PPC. [At least  not
> on  all  processors,  and  if then not for virtual memory but just to
> play dirt^H^H^H^Hclever tricks with the data cache.]

Oh. I see.  Enabling MMU on PPC is just some dirt & clever tricks with
the data cache. I saw the code to enable MMU in start.S. Hmmm...maybe
a bit detail is more helpful to understand why MMU is enabled. Maybe I
need to go back to the processor's user guide.

> > Does ELDK support ARM946? ELDK supports arm920. ELDK can be used for
> > arm946 if its core is compatible with arm920's. If ELDK doesn't
> 
> You can use the cross toolchain, but the ative target tools  will  of
> course not run as they require a standard Linux kernel, not uCLinux.

?? What target tools are you talking about? I thought the target tools
refer to cross compiler, debugger, etc..

Best regards,
-Shawn.

[U-Boot-Users] ARM946, u-boot and linux

[Wolfgang Denk]

In message <c3d0340b040727183672fbbf40@mail.gmail.com> you wrote:
> 
> > You can use the cross toolchain, but the ative target tools  will  of
> > course not run as they require a standard Linux kernel, not uCLinux.
> 
> ?? What target tools are you talking about? I thought the target tools
> refer to cross compiler, debugger, etc..

No. The cross tools are those running on a cross development host, i.
e. for example on a x86 based Linux PC; the target  tools  are  tools
and  libraries  that  will  be running on the target system, i. e. in
your case on the ARM946 processor.

The cross tools  live  in  the  /opt/eldk/bin  and  /opt/eldk/usr/bin
directories, while the target tools vive in /opt/eldk/<target_arch>/

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
1 1 was a race-horse, 2 2 was 1 2. When 1 1 1 1 race, 2 2 1 1 2.