Re: Fwd: [PATCH] Reboot Dreamcast under software control

[Paul M. <le...@li...>]

On Mon, Jul 30, 2007 at 08:49:27PM +0100, Adrian McMenamin wrote:
> On Mon, 2007-07-30 at 07:50 +0900, Paul Mundt wrote:
> > On Sun, Jul 29, 2007 at 07:25:21PM +0100, Adrian McMenamin wrote:
> > > diff --git a/arch/sh/kernel/process.c b/arch/sh/kernel/process.c
> > > index 6334a4c..6f5e9e4 100644
> > > --- a/arch/sh/kernel/process.c
> > > +++ b/arch/sh/kernel/process.c
> > > @@ -97,6 +97,11 @@ void cpu_idle(void)
> > > 
> > >  void machine_restart(char * __unused)
> > >  {
> > > +
> > > +#ifdef CONFIG_SH_DREAMCAST
> > > +       /*reboot the Dreamcast under software control*/
> > > +       writel(0x00007611, 0xA05F6890);
> > > +#endif
> > >         /* SR.BL=1 and invoke address error to let CPU reset (manual reset) */
> > >         asm volatile("ldc %0, sr\n\t"
> > >                      "mov.l @%1, %0" : : "r" (0x10000000), "r" (0x80000001));
> > 
> > No, if you want to do this, at least use a function pointer and leave
> > this as the default implementation. The dreamcast presumably only needs
> > this magic write anyways, rather than the SR.BL trick.
> > 
> OK, stupid question time: How does the build process know what to link
> with - ie how to overload?
> 
If you look at machine_power_off() you can see how there's a function
pointer nested within it that boards can optionally set to their own
implementations, or if it's unset, we just go with the default behaviour.
Something like that is probably more in line with how we want to go.

On the other hand, this isn't crucial for 2.6.23, and if we're going to
do this for 2.6.24, we should probably consider something more like the
i386 machine_ops for implementing these various bits of functionality,
rather than abusing some of the tie-in with the pm ops.

I'll take a look at cobbling something together for the 2.6.24 dev tree,
and move some of the boards over to it. It should be pretty apparent from
this how to wire it up on the dreamcast, with the restart functionality
you're after.