On Thu, Jun 27, 2002 at 02:21:30PM +0200, Maciej W. Rozycki wrote:
> On Wed, 26 Jun 2002, Ladislav Michl wrote:
>
> > +int be_ip22_handler(struct pt_regs *regs, int is_fixup)
> > +{
> > + save_and_clear_buserr();
> > + if (nofault) {
> > + nofault = 0;
> > + compute_return_epc(regs);
> > + return MIPS_BE_DISCARD;
> > + }
> > + return MIPS_BE_FIXUP;
> > +}
>
> I wouldn't use nofault -- it leads to reentrancy problems and I don't
> think you really need it. You probably need to code it like this:
>
> {
> save_and_clear_buserr();
>
> return is_fixup ? MIPS_BE_FIXUP : MIPS_BE_FATAL;
> }
>
> unless:
>
> 1. There is a condition when for is_fixup true you should ignore the fixup
> anyway (e.g. what the bus error logic reports is irrelevant to fixups).
> You should choose between MIPS_BE_FATAL and MIPS_BE_DISCARD then.
>
> 2. There is a condition when for is_fixup false, an error is not fatal and
> execution should get restarted. You should return MIPS_BE_DISCARD then.
There are no such conditions (or I'm missing something). I wrote it as
you suggested:
int be_ip22_handler(struct pt_regs *regs, int is_fixup)
{
DBG("BE exception (%s)\n", is_fixup ? "fixup" : "no fixup");
save_and_clear_buserr();
if (is_fixup)
return MIPS_BE_FIXUP;
print_buserr();
return MIPS_BE_FATAL;
}
try to read status register
addr = KSEG1ADDR(gio_slot_base_addr);
DBG("get_dbe\n");
if (!get_dbe(id, addr)) {
... ok
}
> > +int ip22_baddr(unsigned int *val, unsigned long addr)
> > +{
> > + nofault = 1;
> > + *val = *(volatile unsigned int *) addr;
> > + __asm__ __volatile__("nop;nop;nop;nop");
> > + if (nofault) {
> > + nofault = 0;
> > + return 0;
> > + }
> > + return -EFAULT;
> > +}
>
> Why not simply:
>
> {
> int err;
>
> err = get_dbe(*val, (volatile unsigned int *) addr);
>
> return err ? -EFAULT : 0;
> }
>
> It was designed exactly for this purpose. You may consider using "u32"
> instead of "unsigned int" for hardware accesses to assure the type will
> always be 32-bit.
This way gives following result:
get_dbe
BE exception (no fixup)
Dump of MC registers shows that timeout occurs when accessing nonexistant
memory. Of course it is posible return MIPS_BE_DISCARD than (and
regs->cp0_epc += 4), but how to force get_dbe fail then? Not mentioning
that in such case is better to avoid use of get_dbe... Suggestions are
welcome as always.
Thanks a lot,
Ladis
