From 1d80415db64b54141ef02ae58bd2f273d0ac3c38 Mon Sep 17 00:00:00 2001 From: Chirantan Ekbote Date: Thu, 12 Jun 2014 00:18:48 +0900 Subject: clocksource: exynos_mct: Don't reset the counter during boot and resume Unfortunately on some exynos systems, resetting the mct counter also resets the architected timer counter. This can cause problems if the architected timer driver has already been initialized because the kernel will think that the counter has wrapped around, causing a big jump in printk timestamps and delaying any scheduled clock events until the counter reaches the value it had before it was reset. The kernel code makes no assumptions about the initial value of the mct counter so there is no reason from a software perspective to clear the counter before starting it. This also fixes the problems described in the previous paragraph. Cc: Olof Johansson Cc: Tomasz Figa Signed-off-by: Chirantan Ekbote Reviewed-by: Doug Anderson Tested-by: Doug Anderson Signed-off-by: Kukjin Kim --- drivers/clocksource/exynos_mct.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) (limited to 'drivers/clocksource') diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c index 8d6420013a04..f71d55f5e6e5 100644 --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -153,13 +153,10 @@ static void exynos4_mct_write(unsigned int value, unsigned long offset) } /* Clocksource handling */ -static void exynos4_mct_frc_start(u32 hi, u32 lo) +static void exynos4_mct_frc_start(void) { u32 reg; - exynos4_mct_write(lo, EXYNOS4_MCT_G_CNT_L); - exynos4_mct_write(hi, EXYNOS4_MCT_G_CNT_U); - reg = __raw_readl(reg_base + EXYNOS4_MCT_G_TCON); reg |= MCT_G_TCON_START; exynos4_mct_write(reg, EXYNOS4_MCT_G_TCON); @@ -181,7 +178,7 @@ static cycle_t exynos4_frc_read(struct clocksource *cs) static void exynos4_frc_resume(struct clocksource *cs) { - exynos4_mct_frc_start(0, 0); + exynos4_mct_frc_start(); } struct clocksource mct_frc = { @@ -200,7 +197,7 @@ static u64 notrace exynos4_read_sched_clock(void) static void __init exynos4_clocksource_init(void) { - exynos4_mct_frc_start(0, 0); + exynos4_mct_frc_start(); if (clocksource_register_hz(&mct_frc, clk_rate)) panic("%s: can't register clocksource\n", mct_frc.name); -- cgit v1.2.3 From 89e6a13b88c8bf7ce1011a8a69113f22889f4585 Mon Sep 17 00:00:00 2001 From: Doug Anderson Date: Sat, 5 Jul 2014 06:38:55 +0900 Subject: clocksource: exynos_mct: Fix ftrace In (93bfb76 clocksource: exynos_mct: register sched_clock callback) we supported using the MCT as a scheduler clock. We properly marked exynos4_read_sched_clock() as notrace. However, we then went and called another function that _wasn't_ notrace. That means if you do: cd /sys/kernel/debug/tracing/ echo function_graph > current_tracer You'll get a crash. Fix this (but still let other readers of the MCT be trace-enabled) by adding an extra function. It's important to keep other users of MCT traceable because the MCT is actually quite slow to access and we want exynos4_frc_read() to show up in ftrace profiles if it's the bottleneck. Signed-off-by: Doug Anderson Signed-off-by: Kukjin Kim --- drivers/clocksource/exynos_mct.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'drivers/clocksource') diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c index f71d55f5e6e5..5ce99c07ce8c 100644 --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -162,7 +162,7 @@ static void exynos4_mct_frc_start(void) exynos4_mct_write(reg, EXYNOS4_MCT_G_TCON); } -static cycle_t exynos4_frc_read(struct clocksource *cs) +static cycle_t notrace _exynos4_frc_read(void) { unsigned int lo, hi; u32 hi2 = __raw_readl(reg_base + EXYNOS4_MCT_G_CNT_U); @@ -176,6 +176,11 @@ static cycle_t exynos4_frc_read(struct clocksource *cs) return ((cycle_t)hi << 32) | lo; } +static cycle_t exynos4_frc_read(struct clocksource *cs) +{ + return _exynos4_frc_read(); +} + static void exynos4_frc_resume(struct clocksource *cs) { exynos4_mct_frc_start(); @@ -192,7 +197,7 @@ struct clocksource mct_frc = { static u64 notrace exynos4_read_sched_clock(void) { - return exynos4_frc_read(&mct_frc); + return _exynos4_frc_read(); } static void __init exynos4_clocksource_init(void) -- cgit v1.2.3 From 8bf13a4346996b5a53d5f0c64b0914693c818fc2 Mon Sep 17 00:00:00 2001 From: Amit Daniel Kachhap Date: Sat, 5 Jul 2014 06:40:23 +0900 Subject: clocksource: exynos_mct: Register the timer for stable udelay This patch registers the exynos mct clocksource as the current timer as it has constant clock rate. This will generate correct udelay for the exynos platform and avoid using unnecessary calibrated jiffies. This change has been tested on exynos5420 based board and udelay is very close to expected. Without this patch udelay() on exynos5400 / exynos5800 is wildly inaccurate due to big.LITTLE not adjusting loops_per_jiffy correctly. Also without this patch udelay() on exynos5250 can be innacruate during transitions between frequencies < 800 MHz (you'll go 200 MHz -> 800 MHz -> 300 MHz and will run at 800 MHz for a time with the wrong loops_per_jiffy). [dianders: reworked and created version 3] Signed-off-by: Amit Daniel Kachhap Signed-off-by: Doug Anderson Signed-off-by: Kukjin Kim --- drivers/clocksource/exynos_mct.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'drivers/clocksource') diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c index 5ce99c07ce8c..ab51bf20a3ed 100644 --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -200,10 +200,21 @@ static u64 notrace exynos4_read_sched_clock(void) return _exynos4_frc_read(); } +static struct delay_timer exynos4_delay_timer; + +static cycles_t exynos4_read_current_timer(void) +{ + return _exynos4_frc_read(); +} + static void __init exynos4_clocksource_init(void) { exynos4_mct_frc_start(); + exynos4_delay_timer.read_current_timer = &exynos4_read_current_timer; + exynos4_delay_timer.freq = clk_rate; + register_current_timer_delay(&exynos4_delay_timer); + if (clocksource_register_hz(&mct_frc, clk_rate)) panic("%s: can't register clocksource\n", mct_frc.name); -- cgit v1.2.3