Re: [PATCH 10/14] arm: reimplement startup code in C

[Sascha Hauer <s.hauer@pengutronix.de>]

On Wed, Apr 28, 2010 at 04:32:35AM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 11:03 Fri 23 Apr     , Sascha Hauer wrote:
> > Lets translate the startup code to a language we all understand better.
> > Tested on pcm038 (arm v5) and pcm043 (arm v6).
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  arch/arm/cpu/Makefile              |    6 +-
> >  arch/arm/cpu/start-arm.S           |  248 ------------------------------------
> >  arch/arm/cpu/start.c               |  107 ++++++++++++++++
> >  arch/arm/include/asm/barebox-arm.h |    3 +
> >  arch/arm/lib/barebox.lds.S         |    2 +-
> >  5 files changed, 112 insertions(+), 254 deletions(-)
> >  delete mode 100644 arch/arm/cpu/start-arm.S
> >  create mode 100644 arch/arm/cpu/start.c
> > 
> > diff --git a/arch/arm/cpu/Makefile b/arch/arm/cpu/Makefile
> > index ae1f762..036768e 100644
> > --- a/arch/arm/cpu/Makefile
> > +++ b/arch/arm/cpu/Makefile
> > @@ -1,15 +1,11 @@
> >  obj-y += cpu.o
> >  obj-y += exceptions.o
> >  obj-y += interrupts.o
> > +obj-y += start.o
> >  
> >  #
> >  # Any variants can be called as start-armxyz.S
> >  #
> > -obj-$(CONFIG_CPU_ARM920T) += start-arm.o
> > -obj-$(CONFIG_CPU_ARM926T) += start-arm.o
> > -obj-$(CONFIG_CPU_V7) += start-arm.o
> > -obj-$(CONFIG_ARCH_IMX31) += start-arm.o
> > -obj-$(CONFIG_ARCH_IMX35) += start-arm.o
> >  obj-$(CONFIG_CMD_ARM_CPUINFO) += cpuinfo.o
> >  obj-$(CONFIG_MMU) += mmu.o
> >  obj-$(CONFIG_CPU_32v4T) += cache-armv4.o
> > diff --git a/arch/arm/cpu/start-arm.S b/arch/arm/cpu/start-arm.S
> > deleted file mode 100644
> > index 4d61cee..0000000
> > --- a/arch/arm/cpu/start-arm.S
> > +++ /dev/null
> > @@ -1,248 +0,0 @@
> > -/*
> > +
> > +	/* disable MMU stuff and caches */
> > +	__asm__ __volatile__("mrc p15, 0, %0, c1, c0, 0":"=r"(r));
> > +	r &= ~0x2387; /* clear bits 13, 9:8, 7, 2:0 (--V- --RS B--- -CAM) */
> > +	r |= 0x1002; /* set bit 2 (A) Align, set bit 12 (I) I-Cache */
> can we use here the CP15 macro
> as CR_M and get_cr and set_cr?

We don't have these macros now, eh wait, we do now ;)
I'll send an update soon.

> > +	__asm__ __volatile__("mcr p15, 0, %0, c1, c0, 0" : : "r"(r));
> > +
> > +#ifdef CONFIG_MACH_DO_LOWLEVEL_INIT
> > +	board_init_lowlevel();
> > +#endif
> why not always avoid the ifdef CONFIG_ in the code and define an inline?

Must think about it a bit further. But since this is the old behaviour
lets just keep it for now, we can always change it later.

> > +	board_init_lowlevel_return();
> > +}
> > +
> otherwise it's really easier than the asm to maintain evenif I prefer to write
> it in asm personnaly

The original motivation was to get the pcm043 lowlevel setup smaller so
that for Nand boot the initial code fits better into 2k of memory. I
could have done some hand optimization in the assembler code, but that
would have made it more unreadable. I didn't want to stop then...
We can always look at the resulting disassembly if we want to.

Sascha

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