When the 32k sync timer is used for sched_clock(), it should count
time from the kernel boot (clocksource init) instead of the last HW
reset. Otherwise printk.time values will jump suddenly during the boot:
[ 0.000000] calling omap2_clk_arch_init+0x0/0x138 @ 1
[ 0.000000] initcall omap2_clk_arch_init+0x0/0x138 returned -22
after 0 usecs
[ 0.000000] initcall omap2_clk_arch_init+0x0/0x138 returned with
error code -22
[ 0.000000] calling omap_init_clocksource_32k+0x0/0x98 @ 1
[ 508.697937] initcall omap_init_clocksource_32k+0x0/0x98 returned 0
after 0 usecs
[ 508.697967] calling omap_init_devices+0x0/0x38 @ 1
[ 508.698425] initcall omap_init_devices+0x0/0x38 returned 0 after 0
usecs
This will confuse tools such as scripts/bootgraph.pl.
Signed-off-by: Aaro Koskinen <[email protected]>
Acked-by: Kevin Hilman <[email protected]>
---
v2: Added a comment explaining the offset_32k variable.
The previous version of the patch:
https://patchwork.kernel.org/patch/86945/
arch/arm/plat-omap/common.c | 19 ++++++++++++++-----
1 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/arch/arm/plat-omap/common.c b/arch/arm/plat-omap/common.c
index 088c1a0..bd2df89 100644
--- a/arch/arm/plat-omap/common.c
+++ b/arch/arm/plat-omap/common.c
@@ -100,10 +100,17 @@ EXPORT_SYMBOL(omap_get_var_config);
#include <linux/clocksource.h>
+/*
+ * offset_32k holds the init time counter value. It is then subtracted
+ * from every counter read to achieve a counter that counts time from the
+ * kernel boot (needed for sched_clock()).
+ */
+static u32 offset_32k __read_mostly;
+
#ifdef CONFIG_ARCH_OMAP16XX
static cycle_t omap16xx_32k_read(struct clocksource *cs)
{
- return omap_readl(OMAP16XX_TIMER_32K_SYNCHRONIZED);
+ return omap_readl(OMAP16XX_TIMER_32K_SYNCHRONIZED) - offset_32k;
}
#else
#define omap16xx_32k_read NULL
@@ -112,7 +119,7 @@ static cycle_t omap16xx_32k_read(struct clocksource *cs)
#ifdef CONFIG_ARCH_OMAP2420
static cycle_t omap2420_32k_read(struct clocksource *cs)
{
- return omap_readl(OMAP2420_32KSYNCT_BASE + 0x10);
+ return omap_readl(OMAP2420_32KSYNCT_BASE + 0x10) - offset_32k;
}
#else
#define omap2420_32k_read NULL
@@ -121,7 +128,7 @@ static cycle_t omap2420_32k_read(struct clocksource *cs)
#ifdef CONFIG_ARCH_OMAP2430
static cycle_t omap2430_32k_read(struct clocksource *cs)
{
- return omap_readl(OMAP2430_32KSYNCT_BASE + 0x10);
+ return omap_readl(OMAP2430_32KSYNCT_BASE + 0x10) - offset_32k;
}
#else
#define omap2430_32k_read NULL
@@ -130,7 +137,7 @@ static cycle_t omap2430_32k_read(struct clocksource *cs)
#ifdef CONFIG_ARCH_OMAP3
static cycle_t omap34xx_32k_read(struct clocksource *cs)
{
- return omap_readl(OMAP3430_32KSYNCT_BASE + 0x10);
+ return omap_readl(OMAP3430_32KSYNCT_BASE + 0x10) - offset_32k;
}
#else
#define omap34xx_32k_read NULL
@@ -139,7 +146,7 @@ static cycle_t omap34xx_32k_read(struct clocksource *cs)
#ifdef CONFIG_ARCH_OMAP4
static cycle_t omap44xx_32k_read(struct clocksource *cs)
{
- return omap_readl(OMAP4430_32KSYNCT_BASE + 0x10);
+ return omap_readl(OMAP4430_32KSYNCT_BASE + 0x10) - offset_32k;
}
#else
#define omap44xx_32k_read NULL
@@ -227,6 +234,8 @@ static int __init omap_init_clocksource_32k(void)
clocksource_32k.mult = clocksource_hz2mult(32768,
clocksource_32k.shift);
+ offset_32k = clocksource_32k.read(&clocksource_32k);
+
if (clocksource_register(&clocksource_32k))
printk(err, clocksource_32k.name);
}
--
1.5.6.5
--
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