gemini_prom.s

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/*
 * BK Id: SCCS/s.gemini_prom.S 1.5 05/17/01 18:14:21 cort
 */
/*
 *  arch/ppc/kernel/gemini_prom.S
 *
 *  Not really prom support code (yet), but sort of anti-prom code.  The current
 *  bootloader does a number of things it shouldn't and doesn't do things that it
 *  should.  The stuff in here is mainly a hodge-podge collection of setup code
 *  to get the board up and running.
 *    ---Dan
 */

#include "ppc_asm.tmpl"
#include "ppc_defs.h"
#include <linux/config.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/gemini.h>

#define HID0_ABE (1<<3)

/*
 *  On 750's the MMU is on when Linux is booted, so we need to clear out the
 *  bootloader's BAT settings, make sure we're in supervisor state (gotcha!),
 *  and turn off the MMU.
 *
 */

_GLOBAL(gemini_prom_init)
#ifdef CONFIG_SMP
	/* Since the MMU's on, get stuff in rom space that we'll need */
	lis	r4,GEMINI_CPUSTAT@h
	ori	r4,r4,GEMINI_CPUSTAT@l
	lbz	r5,0(r4)
	andi.	r5,r5,3
	mr	r24,r5		/* cpu # used later on */
#endif
	mfmsr	r4
	li	r3,MSR_PR	/* ensure supervisor! */
	ori	r3,r3,MSR_IR|MSR_DR
	andc	r4,r4,r3
	mtmsr	r4
	isync
#if 0
	/* zero out the bats now that the MMU is off */
prom_no_mmu:	
	li	r3,0
        mtspr   IBAT0U,r3
        mtspr   IBAT0L,r3
        mtspr   IBAT1U,r3
        mtspr   IBAT1L,r3
        mtspr   IBAT2U,r3
        mtspr   IBAT2L,r3
        mtspr   IBAT3U,r3
        mtspr   IBAT3L,r3

        mtspr   DBAT0U,r3
        mtspr   DBAT0L,r3
        mtspr   DBAT1U,r3
        mtspr   DBAT1L,r3
        mtspr   DBAT2U,r3
	mtspr   DBAT2L,r3
        mtspr   DBAT3U,r3
        mtspr   DBAT3L,r3
#endif

	/* the bootloader (as far as I'm currently aware) doesn't mess with page
	   tables, but since we're already here, might as well zap these, too */
	li	r4,0
	mtspr	SDR1,r4

	li	r4,16
	mtctr	r4
	li	r3,0
	li	r4,0
3:	mtsrin	r3,r4
	addi	r3,r3,1
	bdnz	3b

#ifdef CONFIG_SMP
	/* The 750 book (and Mot/IBM support) says that this will "assist" snooping
	   when in SMP.  Not sure yet whether this should stay or leave... */
	mfspr	r4,HID0
	ori	r4,r4,HID0_ABE
	mtspr	HID0,r4
	sync
#endif /* CONFIG_SMP */
	blr

/*  apparently, SMon doesn't pay attention to HID0[SRST].  Disable the MMU and
    branch to 0xfff00100 */
_GLOBAL(_gemini_reboot)
	lis	r5,GEMINI_BOOT_INIT@h
	ori	r5,r5,GEMINI_BOOT_INIT@l
	li	r6,MSR_IP
	mtspr	SRR0,r5
	mtspr	SRR1,r6
	rfi