From b070a03f6490b0ac8d95c51b55a64e433d9160ab Mon Sep 17 00:00:00 2001 From: Oskar Schirmer Date: Mon, 11 May 2009 15:43:36 +0200 Subject: [PATCH] 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 Signed-off-by: Chris Zankel --- arch/xtensa/Kconfig | 1 + arch/xtensa/variants/s6000/Makefile | 1 + arch/xtensa/variants/s6000/delay.c | 27 +++++++++++++++++++++++++++ 3 files changed, 29 insertions(+) create mode 100644 arch/xtensa/variants/s6000/delay.c 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 bool "s6000 - Stretch software configurable processor" select VARIANT_IRQ_SWITCH select ARCH_REQUIRE_GPIOLIB + select XTENSA_CALIBRATE_CCOUNT endchoice config 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 @@ # 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 +#include +#include +#include + +#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)); +} -- 2.30.2