Re: [Patch ARM] Add support for bare-metal cpu initialization on A profile cores.

[Ramana Radhakrishnan <ramrad01 at arm dot com>]

On 09/23/13 04:12, Ye Joey wrote:
> Ramana,
>
> This patch breaks combined build for Cortex-M, i.e., configured with
>
> --with-mode=thumb --with-cpu=cortex-m3
> combine/src/libgloss/arm/cpu-init/rdimon-aem.S:84: Error: thumb
> conditional instruction should be in IT block -- `moveq r4,#0'
>
>
> I think when configured for M-profile, it shouldn't build rdimon-aem.S at all.

Ugggh ... sorry about the breakage.

Agreed - and something's off in the way in which we're multilibbing in 
the cpu-init directory which is why I've not seen this.

The way I'm planning on fixing this is to

* Turn rdimon-aem.S into an empty file for M class cores.
* Force everything into ARM state anyway as it doesn't matter in T32 
state whether one runs cpu-init in ARM or Thumb state.

Patch under testing.

regards
Ramana

> - Joey
>
> On Thu, Sep 19, 2013 at 9:34 PM, Ramana Radhakrishnan <ramrad01@arm.com> wrote:
> > Hi,
> >
> >          Increasingly we've found the need for a start-up routine required
> > for bare-metal applications that need to initialize the mmu and the caches
> > for use during hardware bring-up and/or for bare-metal testing on ARM's
> > propreitary models as well as allow for semi-hosting to happen at the same
> > time. This has been found to be useful in a number of situations and this is
> > just the initial patch set required for this to work on A profile CPUs.  I
> > would recommend that this not be used for earlier cores without testing.
> >
> > The way this is implemented is by adding a new weak function called
> > _rdimon_init_hook that deals with this initialization. I expect this to work
> > on newer hardware because our testing involves testing with the AEM models
> > that model the newer hardware but I don't have access to any such hardware
> > to test this right now.
> >
> > The SMP enable bit in the ACTLR is enabled only for A15 and A7 but not for
> > any other cores as this is needed only on those cores. We use this
> > internally for some of our GCC test runs on our fast models, we've tried it
> > in the past to run some simple applications on bare-metal A7 and A15 boards.
> >
> > This necessitates the use of a new specs file aprofile-ve.specs which I've
> > added and provided as an example. I have tested this on an AEM model but am
> > confident that this will work just fine on a bare-metal board connected via
> > D-Stream or anything that implements the standard Angel API.
> >
> > If people want to use a different base address for the text section and / or
> > for the vectors page in the cpu init code this is available by doing
> > --defsym _rdimon_vector_base=FOO or -Ttext_section=BAR . The specs file only
> > eases the use for this.
> >
> >
> > Tested with an arm-eabi bare-metal GCC multilib build across architecture
> > variants, Thumbness and fpu abi variants using the new specs file in my
> > baremetal build script and tested with --specs=aprofile-ve.specs passed by
> > default in my site.exp - tested on AEM VE model internally .
> >
> >
> > Ok to apply ?
> >
> > regards
> > Ramana
> >
> > <DATE>  Matthew Gretton-Dann  <matthew.gretton-dann@arm.com>
> >       Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
> >       Greta Yorsh  <greta.yorsh@arm.com>
> >
> >          * arm/Makefile.in: Add support for cpu-init directory and add
> >            elf-aprofile-ve.specs.
> >          * arm/configure.in: Likewise.
> >          * arm/configure: Regenerate.
> >          * arm/cpu-init: New directory.
> >          * arm/cpu-init/Makefile.in: New file.
> >          * arm/cpu-init/rdimon-aem.S: Likewise.
> >          * arm/crt0.S: Call _rdimon_init_hook
> >          * arm/elf-aprofile-ve.specs: New file.