aboutsummaryrefslogtreecommitdiffstats
path: root/arch/xtensa
diff options
context:
space:
mode:
authorOskar Schirmer <os@emlix.com>2009-05-11 09:43:36 -0400
committerChris Zankel <chris@zankel.net>2009-05-12 01:00:17 -0400
commitb070a03f6490b0ac8d95c51b55a64e433d9160ab (patch)
tree4715316e494f17980504ee2902a14e1a7d495d05 /arch/xtensa
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')
-rw-r--r--arch/xtensa/Kconfig1
-rw-r--r--arch/xtensa/variants/s6000/Makefile1
-rw-r--r--arch/xtensa/variants/s6000/delay.c27
3 files changed, 29 insertions, 0 deletions
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index 30d21a9e2ef5..ebe228d02b08 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -80,6 +80,7 @@ config XTENSA_VARIANT_S6000
80 bool "s6000 - Stretch software configurable processor" 80 bool "s6000 - Stretch software configurable processor"
81 select VARIANT_IRQ_SWITCH 81 select VARIANT_IRQ_SWITCH
82 select ARCH_REQUIRE_GPIOLIB 82 select ARCH_REQUIRE_GPIOLIB
83 select XTENSA_CALIBRATE_CCOUNT
83endchoice 84endchoice
84 85
85config XTENSA_UNALIGNED_USER 86config XTENSA_UNALIGNED_USER
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 @@
1# s6000 Makefile 1# s6000 Makefile
2 2
3obj-y += irq.o gpio.o 3obj-y += irq.o gpio.o
4obj-$(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 @@
1#include <asm/delay.h>
2#include <asm/timex.h>
3#include <asm/io.h>
4#include <variant/hardware.h>
5
6#define LOOPS 10
7void platform_calibrate_ccount(void)
8{
9 u32 uninitialized_var(a);
10 u32 uninitialized_var(u);
11 u32 b;
12 u32 tstamp = S6_REG_GREG1 + S6_GREG1_GLOBAL_TIMER;
13 int i = LOOPS+1;
14 do {
15 u32 t = u;
16 asm volatile(
17 "1: l32i %0, %2, 0 ;"
18 " beq %0, %1, 1b ;"
19 : "=&a"(u) : "a"(t), "a"(tstamp));
20 b = xtensa_get_ccount();
21 if (i == LOOPS)
22 a = b;
23 } while (--i >= 0);
24 b -= a;
25 nsec_per_ccount = (LOOPS * 10000) / b;
26 ccount_per_jiffy = b * (100000UL / (LOOPS * HZ));
27}