ARM: 8306/1: loop_udelay: remove bogomips value limitation

Now that we don't support ARMv3 anymore, the loop based delay code can
convert microsecs into number of loops using a 64-bit multiplication
and more precision.

This allows us to lift the hard limit of 3355 on the bogomips value as
loops_per_jiffy may now safely span the full 32-bit range.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 12 insertions, 14 deletions

diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h
index dff714d886d5..b7a428154355 100644
--- a/arch/arm/include/asm/delay.h
+++ b/arch/arm/include/asm/delay.h
@@ -10,8 +10,8 @@
 #include <asm/param.h>  /* HZ */
 
 #define MAX_UDELAY_MS   2
-#define UDELAY_MULT     ((UL(2199023) * HZ) >> 11)
-#define UDELAY_SHIFT    30
+#define UDELAY_MULT     UL(2047 * HZ + 483648 * HZ / 1000000)
+#define UDELAY_SHIFT    31
 
 #ifndef __ASSEMBLY__
 
@@ -34,7 +34,7 @@ extern struct arm_delay_ops {
  * it, it means that you're calling udelay() with an out of range value.
  *
  * With currently imposed limits, this means that we support a max delay
- * of 2000us. Further limits: HZ<=1000 and bogomips<=3355
+ * of 2000us. Further limits: HZ<=1000
  */
 extern void __bad_udelay(void);
 
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index d8a780799506..27f4d96258a2 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -29,7 +29,10 @@ else
   lib-y += io-readsw-armv4.o io-writesw-armv4.o
 endif
 
-lib-$(CONFIG_ARCH_RPC)          += ecard.o io-acorn.o floppydma.o
+ifeq ($(CONFIG_ARCH_RPC),y)
+  lib-y                         += ecard.o io-acorn.o floppydma.o
+  AFLAGS_delay-loop.o           += -march=armv4
+endif
 
 $(obj)/csumpartialcopy.o:       $(obj)/csumpartialcopygeneric.S
 $(obj)/csumpartialcopyuser.o:   $(obj)/csumpartialcopygeneric.S
diff --git a/arch/arm/lib/delay-loop.S b/arch/arm/lib/delay-loop.S
index 518bf6e93f78..792c59d885bc 100644
--- a/arch/arm/lib/delay-loop.S
+++ b/arch/arm/lib/delay-loop.S
@@ -10,6 +10,7 @@
 #include <linux/linkage.h>
 #include <asm/assembler.h>
 #include <asm/delay.h>
+
                 .text
 
 .LC0:           .word   loops_per_jiffy
@@ -17,7 +18,6 @@
 
 /*
  * r0  <= 2000
- * lpj <= 0x01ffffff (max. 3355 bogomips)
  * HZ  <= 1000
  */
 
@@ -25,16 +25,11 @@ ENTRY(__loop_udelay)
                 ldr     r2, .LC1
                 mul     r0, r2, r0
 ENTRY(__loop_const_udelay)                      @ 0 <= r0 <= 0x7fffff06
-                mov     r1, #-1
                 ldr     r2, .LC0
-                ldr     r2, [r2]                @ max = 0x01ffffff
-                add     r0, r0, r1, lsr #32-14
-                mov     r0, r0, lsr #14         @ max = 0x0001ffff
-                add     r2, r2, r1, lsr #32-10
-                mov     r2, r2, lsr #10         @ max = 0x00007fff
-                mul     r0, r2, r0              @ max = 2^32-1
-                add     r0, r0, r1, lsr #32-6
-                movs    r0, r0, lsr #6
+                ldr     r2, [r2]
+                umull   r1, r0, r2, r0
+                adds    r1, r1, #0xffffffff
+                adcs    r0, r0, r0
                 reteq   lr
 
 /*