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 <aaro.koskinen@xxxxxxxxx> Acked-by: Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
