[U-Boot] [PATCH] tegra20: add back USE_PRIVATE_LIBGCC

[Allen Martin]

On Tue, Aug 07, 2012 at 03:42:45PM -0700, Lucas Stach wrote:
> Am Dienstag, den 07.08.2012, 15:28 -0700 schrieb Allen Martin:
> > On Tue, Aug 07, 2012 at 10:53:00AM -0700, Lucas Stach wrote:
> > > Hi Allen,
> > > 
> > > And to answer Tom's question: the failure was that the real U-Boot would
> > > not come up after the SPL. All I could see was the one line printed by
> > > the SPL and nothing more.
> > 
> > I think I found the problem.  It's the following code from start.S:
> > 
> > ENTRY(cpu_init_crit)
> >        /*
> >         * Jump to board specific initialization...
> >         * The Mask ROM will have already initialized
> >         * basic memory. Go here to bump up clock rate and handle
> >         * wake up conditions.
> >         */
> >        mov     ip, lr                  @ persevere link reg across
> >        call
> >        bl      lowlevel_init           @ go setup pll,mux,memory
> >        mov     lr, ip                  @ restore link
> >        mov     pc, lr                  @ back to my caller
> > ENDPROC(cpu_init_crit)
> > 
> > 
> > The "ip" register is not preserved across function calls, and the
> > CodeSourcery compiler is using it in lowlevel_init or one of the
> > functions it calls.  This code was there before the SPL changes, but
> > wasn't being called because CONFIG_SKIP_LOWLEVEL_INIT was set, but now
> > it isn't.
> > 
> > Lucas, can you try the following change?  I tested it on seaboard with
> > CodeSourcery arm-2011.09-70-arm-none-linux-gnueabi and I'm able to
> > boot a kernel.
> 
> Yes I can confirm this fixes the issue without further workarounds.
> Thanks, and:
> 
> Tested-by: Lucas Stach <dev at lynxeye.de>

Digging a little deeper into this, cpu_init_crit() and lowlevel_init()
are called before the stack is setup, so the fact that we call into C
code on tegra here is probably the bigger issue.  I think the correct
fix here is for me to move the code from lowlevel_init() to
board_init_f(). 

-Allen
-- 
nvpublic