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authorOskar Schirmer <os@emlix.com>2009-05-11 15:43:36 +0200
committerChris Zankel <chris@zankel.net>2009-05-11 22:00:17 -0700
commitb070a03f6490b0ac8d95c51b55a64e433d9160ab (patch)
tree4715316e494f17980504ee2902a14e1a7d495d05 /arch/xtensa/variants
parentd15f05eb8cc4ad59699c16b8ae834b85c6d39bfe (diff)
xtensa: implement ccount calibration for s6000
Calculate core frequency from timers at boot time instead of assuming a fixed frequency. This is useful as the true frequency is set up by the boot loader, thus variable. Signed-off-by: Oskar Schirmer <os@emlix.com> Signed-off-by: Chris Zankel <chris@zankel.net>
Diffstat (limited to 'arch/xtensa/variants')
-rw-r--r--arch/xtensa/variants/s6000/Makefile1
-rw-r--r--arch/xtensa/variants/s6000/delay.c27
2 files changed, 28 insertions, 0 deletions
diff --git a/arch/xtensa/variants/s6000/Makefile b/arch/xtensa/variants/s6000/Makefile
index 03b3975468bd..d83f3805130c 100644
--- a/arch/xtensa/variants/s6000/Makefile
+++ b/arch/xtensa/variants/s6000/Makefile
@@ -1,3 +1,4 @@
# s6000 Makefile
obj-y += irq.o gpio.o
+obj-$(CONFIG_XTENSA_CALIBRATE_CCOUNT) += delay.o
diff --git a/arch/xtensa/variants/s6000/delay.c b/arch/xtensa/variants/s6000/delay.c
new file mode 100644
index 000000000000..54b2b573f166
--- /dev/null
+++ b/arch/xtensa/variants/s6000/delay.c
@@ -0,0 +1,27 @@
+#include <asm/delay.h>
+#include <asm/timex.h>
+#include <asm/io.h>
+#include <variant/hardware.h>
+
+#define LOOPS 10
+void platform_calibrate_ccount(void)
+{
+ u32 uninitialized_var(a);
+ u32 uninitialized_var(u);
+ u32 b;
+ u32 tstamp = S6_REG_GREG1 + S6_GREG1_GLOBAL_TIMER;
+ int i = LOOPS+1;
+ do {
+ u32 t = u;
+ asm volatile(
+ "1: l32i %0, %2, 0 ;"
+ " beq %0, %1, 1b ;"
+ : "=&a"(u) : "a"(t), "a"(tstamp));
+ b = xtensa_get_ccount();
+ if (i == LOOPS)
+ a = b;
+ } while (--i >= 0);
+ b -= a;
+ nsec_per_ccount = (LOOPS * 10000) / b;
+ ccount_per_jiffy = b * (100000UL / (LOOPS * HZ));
+}

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