powerpc/time: refactor MFTB() to limit number of ifdefs

The 8xx cannot access the TBL and TBU registers using mfspr/mtspr
It must be accessed using mftb/mftbu

Due to this, there is a number of places with #ifdef CONFIG_8xx

This patch defines new macros MFTBL(x) and MFTBU(x) on the same model
as MFTB(x) and tries to make use of them as much as possible.

In arch/powerpc/include/asm/timex.h, we also remove the ifdef
for the asm() operands as the compiler doesn't mind unused operands

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/boot/ppc_asm.h

@@ -80,4 +80,12 @@
 	.long 0xa6037b7d; /* mtsrr1 r11				*/ \
 	.long 0x2400004c  /* rfid				*/
 
+#ifdef CONFIG_PPC_8xx
+#define MFTBL(dest)			mftb dest
+#define MFTBU(dest)			mftbu dest
+#else
+#define MFTBL(dest)			mfspr dest, SPRN_TBRL
+#define MFTBU(dest)			mfspr dest, SPRN_TBRU
+#endif
+
 #endif /* _PPC64_PPC_ASM_H */

arch/powerpc/boot/util.S

@@ -71,32 +71,18 @@ udelay:
 	add	r4,r4,r5
 	addi	r4,r4,-1
 	divw	r4,r4,r5	/* BUS ticks */
-#ifdef CONFIG_8xx
-1:	mftbu	r5
-	mftb	r6
-	mftbu	r7
-#else
-1:	mfspr	r5, SPRN_TBRU
-	mfspr	r6, SPRN_TBRL
-	mfspr	r7, SPRN_TBRU
-#endif
+1:	MFTBU(r5)
+	MFTBL(r6)
+	MFTBU(r7)
 	cmpw	0,r5,r7
 	bne	1b		/* Get [synced] base time */
 	addc	r9,r6,r4	/* Compute end time */
 	addze	r8,r5
-#ifdef CONFIG_8xx
-2:	mftbu	r5
-#else
-2:	mfspr	r5, SPRN_TBRU
-#endif
+2:	MFTBU(r5)
 	cmpw	0,r5,r8
 	blt	2b
 	bgt	3f
-#ifdef CONFIG_8xx
-	mftb	r6
-#else
-	mfspr	r6, SPRN_TBRL
-#endif
+	MFTBL(r6)
 	cmpw	0,r6,r9
 	blt	2b
 3:	blr