Possible bug in PPC4xx dcache() function

Greetings!

If I call the dflush() function in cpu/ppc4xx/start.S on a PPC440EPx as part of initializing SDRAM, I later get the error

    The value of DVLIM special register is incorrect: 0x00000000

from spr_post_test(). I can make the spr_post_test() error message go away by applying the patch

@@ -1711,6 +1711,7 @@ trap_reloc:
 	rlwinm	r8,r9,0,15,13
 	rlwinm	r8,r8,0,17,15
 	mtmsr	r8
+	mfspr	r8,dvlim
 	addi	r3,r0,0x0000
 	mtspr	dvlim,r3
 	mfspr	r3,ivpr

@@ -1725,6 +1726,7 @@ trap_reloc:
 ..ag:	dcbf	r0,r3
 	addi	r3,r3,-32
 	bdnz	..ag
+	mtspr	dvlim,r8
 	sync
 	mtmsr	r9
 	blr

The routine dflush() zeros DVLIM but does not save and restore the original value. Is this the intended behavior? The patch I tried seems safe, although I couldn't easily find the gcc function calling conventions for PowerPC. (Does anyone have a pointer to these?)

-- Best regards, Larry Johnson <[email protected]>