Execute Reset via CheckStop approach

[bart at ardistech.com]

Hi Wolfgang,

> The DER should be set by your formware. Fix this!
>
I cleared CFG_DER in ppcboot to clear the CHSTP bit. After that I needed to
map in the br0 range and to make the asm's volatile and set the input/output
parameters of the asm to get the HRESET_N pulse. So this is the version
which works (on a MPC823e) in the context of the Linux kernel:

        /* Get base address mapped by BR0/OR0 and map it in */
        val = ((immap_t *)IMAP_ADDR)->im_memctl.memc_br0 & 0xFFFF8000;
	val = (int) ioremap( retval, 0x4000 );
        cli();

        /* Enable CheckStop Reset */
        ((immap_t *)IMAP_ADDR)->im_clkrst.car_plprcr |= 0x00000080;

        /* Invalidate BR0 mapping */
        ((immap_t *)IMAP_ADDR)->im_memctl.memc_br0 &= ~0x1;

        /* Clear ME in MSR and cause CheckStop */
        __asm__ volatile("mfmsr %0" : "=r" (msr) );
        msr &= ~0x1000;
        __asm__ volatile("mtmsr %0": : "r" (msr) );
        val = * (unsigned char *) val;
        printk("Restart failed\n");
        while(1)
	   ;

Cheers,
	Bart

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