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authorWill Deacon <will.deacon@arm.com>2012-07-06 15:47:17 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2012-07-09 17:42:23 +0100
commitd0a533b18235d36206b9b422efadb7cee444dfdb (patch)
tree43dcdcf9eebd9c88430df031305ca4eb5c2346f4 /arch/arm/lib/delay-loop.S
parent923df96b9f31b7d08d8438ff9677326d9537accf (diff)
downloadlinux-linaro-stable-d0a533b18235d36206b9b422efadb7cee444dfdb.tar.gz
ARM: 7452/1: delay: allow timer-based delay implementation to be selected
This patch allows a timer-based delay implementation to be selected by switching the delay routines over to use get_cycles, which is implemented in terms of read_current_timer. This further allows us to skip the loop calibration and have a consistent delay function in the face of core frequency scaling. To avoid the pain of dealing with memory-mapped counters, this implementation uses the co-processor interface to the architected timers when they are available. The previous loop-based implementation is kept around for CPUs without the architected timers and we retain both the maximum delay (2ms) and the corresponding conversion factors for determining the number of loops required for a given interval. Since the indirection of the timer routines will only work when called from C, the sa1100 sleep routines are modified to branch to the loop-based delay functions directly. Tested-by: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/lib/delay-loop.S')
-rw-r--r--arch/arm/lib/delay-loop.S67
1 files changed, 67 insertions, 0 deletions
diff --git a/arch/arm/lib/delay-loop.S b/arch/arm/lib/delay-loop.S
new file mode 100644
index 000000000000..36b668d8e121
--- /dev/null
+++ b/arch/arm/lib/delay-loop.S
@@ -0,0 +1,67 @@
+/*
+ * linux/arch/arm/lib/delay.S
+ *
+ * Copyright (C) 1995, 1996 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/linkage.h>
+#include <asm/assembler.h>
+#include <asm/delay.h>
+ .text
+
+.LC0: .word loops_per_jiffy
+.LC1: .word UDELAY_MULT
+
+/*
+ * r0 <= 2000
+ * lpj <= 0x01ffffff (max. 3355 bogomips)
+ * HZ <= 1000
+ */
+
+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
+ moveq pc, lr
+
+/*
+ * loops = r0 * HZ * loops_per_jiffy / 1000000
+ */
+
+@ Delay routine
+ENTRY(__loop_delay)
+ subs r0, r0, #1
+#if 0
+ movls pc, lr
+ subs r0, r0, #1
+ movls pc, lr
+ subs r0, r0, #1
+ movls pc, lr
+ subs r0, r0, #1
+ movls pc, lr
+ subs r0, r0, #1
+ movls pc, lr
+ subs r0, r0, #1
+ movls pc, lr
+ subs r0, r0, #1
+ movls pc, lr
+ subs r0, r0, #1
+#endif
+ bhi __loop_delay
+ mov pc, lr
+ENDPROC(__loop_udelay)
+ENDPROC(__loop_const_udelay)
+ENDPROC(__loop_delay)