powerpc/85xx: resize the boot page TLB before relocating CCSR

On some Freescale systems (e.g. those booted from the on-chip ROM), the
TLB that covers the boot page can also cover CCSR, which breaks the CCSR
relocation code.  To fix this, we resize the boot page TLB so that it only
covers the 4KB boot page.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/cpu/mpc85xx/start.S

@@ -318,6 +318,55 @@ l2_disabled:
 
 #endif /* CONFIG_MPC8569 */
 
+/*
+ * Search for the TLB that covers the code we're executing, and shrink it
+ * so that it covers only this 4K page.  That will ensure that any other
+ * TLB we create won't interfere with it.  We assume that the TLB exists,
+ * which is why we don't check the Valid bit of MAS1.
+ *
+ * This is necessary, for example, when booting from the on-chip ROM,
+ * which (oddly) creates a single 4GB TLB that covers CCSR and DDR.
+ * If we don't shrink this TLB now, then we'll accidentally delete it
+ * in "purge_old_ccsr_tlb" below.
+ */
+	bl	nexti		/* Find our address */
+nexti:	mflr	r1		/* R1 = our PC */
+	li	r2, 0
+	mtspr	MAS6, r2	/* Assume the current PID and AS are 0 */
+	isync
+	msync
+	tlbsx	0, r1		/* This must succeed */
+
+	/* Set the size of the TLB to 4KB */
+	mfspr	r3, MAS1
+	li	r2, 0xF00
+	andc	r3, r3, r2	/* Clear the TSIZE bits */
+	ori	r3, r3, MAS1_TSIZE(BOOKE_PAGESZ_4K)@l
+	mtspr	MAS1, r3
+
+	/*
+	 * Set the base address of the TLB to our PC.  We assume that
+	 * virtual == physical.  We also assume that MAS2_EPN == MAS3_RPN.
+	 */
+	lis	r3, MAS2_EPN@h
+	ori	r3, r3, MAS2_EPN@l	/* R3 = MAS2_EPN */
+
+	and	r1, r1, r3	/* Our PC, rounded down to the nearest page */
+
+	mfspr	r2, MAS2
+	andc	r2, r2, r3
+	or	r2, r2, r1
+	mtspr	MAS2, r2	/* Set the EPN to our PC base address */
+
+	mfspr	r2, MAS3
+	andc	r2, r2, r3
+	or	r2, r2, r1
+	mtspr	MAS3, r2	/* Set the RPN to our PC base address */
+
+	isync
+	msync
+	tlbwe
+
 /*
  * Relocate CCSR, if necessary.  We relocate CCSR if (obviously) the default
  * location is not where we want it.  This typically happens on a 36-bit