[U-Boot] Prefetch abort exception

[Albert ARIBAUD <albert.u.boot@aribaud.net>]

Hi Parimala,

On Thu, 16 Jan 2014 17:55:10 +0530, Parimala Baggiri
<baggiriparimala@gmail.com> wrote:

> Hello,
> 
> On Tue, Jan 14, 2014 at 11:30 AM, Albert ARIBAUD
> <albert.u.boot@aribaud.net>wrote:
> 
> > Hi Parimala,
> >
> > On Mon, 13 Jan 2014 19:00:04 +0530, Parimala Baggiri
> > <baggiriparimala@gmail.com> wrote:
> >
> > > Hello,
> > >
> > > I have added interrupt support for armv7 platform, by implementing the
> > > do_irq and irq_install_handler and arch_interrupt_init functions.
> > >
> > > Initially default_isr is the handler function installed for all the
> > > interrupts.
> > >
> > > From my standalone application, I am enabling the interrupts and
> > installing
> > > the handler to be called for my peripheral interrupt.
> > >
> > > If I don't install my handler, U-Boot executes default_isr successfully.
> > >
> > > If I use my handler, when the interrupt occurs I am getting the prefetch
> > > abort exception with the following dump
> > > prefetch abort
> > > pc : [<ebd78002>]          lr : [<bff8f720>]
> > > sp : bfeef200  ip : bfeef358     fp : bfef1d48
> > > r10: bfef1d78  r9 : 00000002     r8 : bfeeff58
> > > r7 : bffac284  r6 : 60000153     r5 : bffbb5c0  r4 : 00000000
> > > r3 : bffab29c  r2 : 00000000     r1 : 000003e8  r0 : 8500178c
> > > Flags: nZCv  IRQs off  FIQs off  Mode IRQ_32
> > > Resetting CPU ...
> > >
> > > resetting ...
> > >
> > > U-Boot SPL 2013.01.-rc1-00003-g43ee87a-dirty (Jan 10 2014 - 16:04:35)
> > > OMAP4460 ES1.1
> > > OMAP SD/MMC: 0
> > > reading u-boot.img
> > > reading u-boot.img
> > >
> > > Can any one please help me to solve this?
> >
> > You're the best suited to tell, since you're the only one who can read
> > or test the code, so the following question is just a wild guess: does
> > the interrupt handler properly save (and restore) the interrupted
> > context, and does it properly establish (and dispose of) its own
> > context?
> >
> > Thank you all for the suggestions
> I found that, using "printf" statement within my ISR is causing the
> prefetch abort.

Well, it usually isn't a good idea to try and use such functions as
printf() within an interrupt handler, if only because you might have
interrupted a call to printf(), and printf() might not be re-entrant,
which could explain the abort you see.

Besides, even with a re-entrant printf() implementation, interrupting
printf() to do a printf() will propably result in mangled output.

> Regards,
> Parimala

Amicalement,
-- 
Albert.