On Wed, 2010-03-17 at 16:02 +0100, Ralf Baechle wrote:
> On Sat, Mar 13, 2010 at 12:34:17PM +0800, Wu Zhangjin wrote:
>
> > - /* reboot via jumping to boot base address */
> > + /* reboot via jumping to boot base address
> > + *
> > + * ".set noat" and ".set at" are used to ensure the address not break
> > + * by the -mfix-loongson2f-jump option provided by binutils 2.20.1 (or
> > + * higher version) which try to change the jumping address to "addr &
> > + * 0xcfffffff" via the at($1) register, this is totally wrong for
> > + * 0xbfc00000 (LOONGSON_BOOT_BASE).
> > + */
> > + __asm__ __volatile__(".set noat\n");
> > ((void (*)(void))ioremap_nocache(LOONGSON_BOOT_BASE, 4)) ();
> > + __asm__ __volatile__(".set at\n");
>
> Ouch. This is fragile and totally puts the kernels fate at the mercy of
> gcc and the ioremap_nocache() implementation. GCC might emit a .set noat
> at any time. Something like
>
> void loongson_restart(char *command)
> {
> void (*func)(void);
>
> /* do preparation for reboot */
> mach_prepare_reboot();
>
> /* reboot via jumping to boot base address */
> func = (void *) ioremap_nocache(LOONGSON_BOOT_BASE, 4);
>
> __asm__ __volatile__(
> " .set noat \n"
> " jr %[func] \n"
> " .set at \n"
> : /* No outputs */
> : [func] "r" (func));
> }
>
> should be safe against -mfix-loongson2f-jump I think.
Thanks very much, will apply it in the revision of this patch.
Regards,
Wu Zhangjin
