Cortex-M3 support?

[xu ray]

2009/7/29 Mike Panetta <mprtems at bellsouth.net>

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> ----- Original Message ----
> > From: Joel Sherrill <joel.sherrill at oarcorp.com>
> > To: Mike Panetta <mprtems at bellsouth.net>; "rtems-users at rtems.org" <
> rtems-users at rtems.org>
> > Sent: Friday, July 24, 2009 10:41:21 AM
> > Subject: Re: Cortex-M3 support?
> >
> > Sebastian Huber has been reworking the ARM exception code so
> > make sure you are on today's head and talking to him.
>
> I don't have his email address, should it be in the list archives?
> He has not posted recently in reply to this message, so I am
> not quite sure how to contact him.
>

Add Sebastian Huber in the loop. He might be busy with LPC porting now.


>
> >
> > In general terms, you want to start with the CPU core and
> > ignore the peripherals.
> >
> > + make sure the multilib variant is in the tools
> > + make sure the multilib variant is properly supported
> >    by cpukit/score/arm and the libnetworking cksum routines.
>
> Its in the tools, but the score code seems to be dependent on
> non thumb ASM so it will not compile for the Cortex-M3.
>
> Specifically the context switching code is explicitly in ARM mode.
>

You can refer to make/custom/rtl22xx_t.cfg and rtl22xx_t BSP. This is a
Thumb BSP. Try the "-mcpu=cortex-m3 -mthumb" flag for cortext-m3. I think no
one have ever tried the cortex-m3 flag with rtems tool chain yet, hoping it
works for you. Btw, minimum code size for rtl22xx_t is about 16K with 2K
.bss/.data space, and the binary removed the  filesystem and libc overhead.
What is your requirement for RAM and ROM space?

For the assembly code. The cortex family does not need to change to ARM mode
when run the privilege instructions. So you can change the mode switch macro
like align.  Furthermore, cortex adds some registers like basepri, psp which
is critical to the thread switch. You will have to add code to handle these.



>
> >
> > If you have a non-RTEMS "no OS" arm-elf toolset which can
> > produce working executables for you, then you are almost
> > ready for a very minimal BSP.
> >
> > + Use the linker script as base with additions for
> >    workspace related symbols
> > + Use the crt0.S from it (change call main -> boot_card)
> > + implement a polled console using the libgloss support.
> > + Use the "dummy idle task clock driver"
>
> As soon as I can figure the best way to get the score code to
> compile that will be my next step, using the rtems supplied tools. :)
>
> >
> > At the moment, I think the avr, m32c, adn m32r BSPs are the closest
> > examples to this minimal point.
> >
> > That gives you enough to run tests with no interrupts.
> >
> > Sebastian will need to step in for exception processing.
>
> Waiting to hear from him.
>
> >
>
> Thanks again,
> Mike
>
> >
> > -- Joel Sherrill, Ph.D.             Director of Research & Development
> > joel.sherrill at OARcorp.com        On-Line Applications Research
> > Ask me about RTEMS: a free RTOS  Huntsville AL 35805
> >   Support Available             (256) 722-9985
>
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>



-- 
Thanks & Best Regards!

Ray, Xu
PEP Technology
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