reboot by software

Wolfgang Denk wd at
Tue Dec 16 21:24:51 EST 2003

Dear John,

in message <000101c3c3b8$68333110$b702a8c0 at newrock2> you wrote:
> I have a linux running on my mpc8260 board( power on reset at
> 0xfff00100, I use 32 bit flash, and directly maping 0xF0000000 ~
> 0xFFFFFFF in kernel).
> Now, I want to reboot system by software. But, when I jump to
> 0xfff00100 in kernel mode, it's going dead. Can anybody help me?

Jumping to some address does not cause a reboot of the system.  After
a   reset,  the  CPU  state  (especially  the  state  of  the  memory
controller) is somewhat special. The safest  way  to  cause  a  clean
reboot of the whole system is to actually go through a reset.

Try something like this:

m8260_restart(char *cmd)
	__volatile__	unsigned char	dummy;
	__volatile__	unsigned int	msr;
	uint		bad_addr;

	/* Get base address mapped by BR0/OR0 */
	bad_addr = ((immap_t *)IMAP_ADDR)->im_memctl.memc_br0 & 0xFFFF8000;

	/* Enable CheckStop Reset */
	((immap_t *)IMAP_ADDR)->im_clkrst.car_rmr |= 0x00000001;

	/* Invalidate BR0 mapping */
	((immap_t *)IMAP_ADDR)->im_memctl.memc_br0 = 0;

	/* Set MSR and cause reset */
	__asm__("mfmsr %0" : "=r" (msr) );
	msr &= ~0x1000;
	__asm__("mtmsr %0" : "=r" (msr) );
	dummy = * (unsigned char *) bad_addr;
	printk("Restart failed\n");

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at
Bankers do it with interest (penalty for early withdrawal).

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