[PATCH v5] clocksource:arm_global_timer: Add ARM global timer support.

[PATCH v5] clocksource:arm_global_timer: Add ARM global timer support.

[Srinivas KANDAGATLA]

From: Stuart Menefy <stuart.menefy@st.com>

This is a simple driver for the global timer module found in the Cortex
A9-MP cores from revision r1p0 onwards. This should be able to perform
the functions of the system timer and the local timer in an SMP system.

The global timer has the following features:
    The global timer is a 64-bit incrementing counter with an
auto-incrementing feature. It continues incrementing after sending
interrupts. The global timer is memory mapped in the private memory
region.
    The global timer is accessible to all Cortex-A9 processors in the
cluster. Each Cortex-A9 processor has a private 64-bit comparator that
is used to assert a private interrupt when the global timer has reached
the comparator value. All the Cortex-A9 processors in a design use the
banked ID, ID27, for this interrupt. ID27 is sent to the Interrupt
Controller as a Private Peripheral Interrupt. The global timer is
clocked by PERIPHCLK.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
CC: Arnd Bergmann <arnd@arndb.de>
CC: Rob Herring <robherring2@gmail.com>
CC: Linus Walleij <linus.walleij@linaro.org>
CC: Will Deacon <will.deacon@arm.com>
CC: Thomas Gleixner <tglx@linutronix.de>
---

Thankyou for reveiwing the v4 patch.
This patch is split out of the orignal 10 patches submitted for Stixxxx SOC
support to arm-kernel mailing list. This patch has undergone 3 cycles of
reviews in arm-kernel mailing list.

Arnd already picked up SOC support patches [4-10] and merged them via arm-soc
tree for 3.11.

If its not too late can this patch be considered for 3.11 via clocksource tree?
This patch has no build dependencies.

Thanks,
srini

Changes since v4:
	All the comments are from Thomas G.
	- disabled irq and comp enable bits while setting one-shot mode.
	- remove double pointer usage of clock_event_device structure.
	- remove spaces from device name.
	- remove few un-necessary comments.
	- Fix error checks and error case handling in global_timer_of_register

Changes since v3:
	- Arnd suggested to replaced all __raw_readl/__raw_writel with
	readl/writel or readl_relaxed/writel_relaxed(for optimized path)
	as __raw* apis are not Endian safe.

Changes since v2:
	- cleaned up arm-global-timer code for non-dt as suggested by Linus W and
	- fixed minmum clock tick setting pointed by Linus W.

Changes since RFC:
	Most of the comments are suggested by Linus W.
	- moved to drivers/clocksource.
	- added revision check in driver.
	- removed unused header file.
	- moved to u64 from union gt_counter
	- comments added in get_counter
	- removed leftover debug code.
	- moved code to use __raw_readl/writel.
	- used DIV_ROUND_CLOSEST
	- added check in interrupt handler.
	- expanded CE and CS acronyms usage.
	- Fixed minimum clock ticks value.
	- move to use clocksource_register_hz
	- added arch sched_clock support.
	- added ERRATA 740657 workaround.
 .../devicetree/bindings/arm/global_timer.txt       |   21 ++
 drivers/clocksource/Kconfig                        |   13 +
 drivers/clocksource/Makefile                       |    1 +
 drivers/clocksource/arm_global_timer.c             |  320 ++++++++++++++++++++
 4 files changed, 355 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/arm/global_timer.txt
 create mode 100644 drivers/clocksource/arm_global_timer.c

diff --git a/Documentation/devicetree/bindings/arm/global_timer.txt b/Documentation/devicetree/bindings/arm/global_timer.txt
new file mode 100644
index 0000000..b64abac
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/global_timer.txt
@@ -0,0 +1,21 @@
+
+* ARM Global Timer
+	Cortex-A9 are often associated with a per-core Global timer.
+
+** Timer node required properties:
+
+- compatible : Should be "arm,cortex-a9-global-timer"
+		Driver supports versions r2p0 and above.
+
+- interrupts : One interrupt to each core
+
+- reg : Specify the base address and the size of the GT timer
+	register window.
+
+Example:
+
+	timer@2c000600 {
+		compatible = "arm,cortex-a9-global-timer";
+		reg = <0x2c000600 0x20>;
+		interrupts = <1 13 0xf01>;
+	};
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 5871933..33e4453 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -69,6 +69,19 @@ config ARM_ARCH_TIMER
 	bool
 	select CLKSRC_OF if OF
 
+config ARM_GLOBAL_TIMER
+	bool
+	select CLKSRC_OF if OF
+	help
+	  This options enables support for the ARM global timer unit
+
+config CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
+	bool
+	depends on ARM_GLOBAL_TIMER
+	default y
+	help
+	 Use ARM global timer clock source as sched_clock
+
 config CLKSRC_METAG_GENERIC
 	def_bool y if METAG
 	help
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 8d979c7..b2363cb 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -28,4 +28,5 @@ obj-$(CONFIG_CLKSRC_EXYNOS_MCT)	+= exynos_mct.o
 obj-$(CONFIG_CLKSRC_SAMSUNG_PWM)	+= samsung_pwm_timer.o
 
 obj-$(CONFIG_ARM_ARCH_TIMER)		+= arm_arch_timer.o
+obj-$(CONFIG_ARM_GLOBAL_TIMER)		+= arm_global_timer.o
 obj-$(CONFIG_CLKSRC_METAG_GENERIC)	+= metag_generic.o
diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c
new file mode 100644
index 0000000..8ae6e01
--- /dev/null
+++ b/drivers/clocksource/arm_global_timer.c
@@ -0,0 +1,320 @@
+/*
+ * drivers/clocksource/arm_global_timer.c
+ *
+ * Copyright (C) 2013 STMicroelectronics (R&D) Limited.
+ * Author: Stuart Menefy <stuart.menefy@st.com>
+ * Author: Srinivas Kandagatla <srinivas.kandagatla@st.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/clk.h>
+#include <linux/clkdev.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
+
+#include <asm/sched_clock.h>
+#include <asm/mach/irq.h>
+#include <asm/cputype.h>
+#include <asm/localtimer.h>
+
+#define GT_COUNTER0	0x00
+#define GT_COUNTER1	0x04
+
+#define GT_CONTROL	0x08
+#define GT_CONTROL_TIMER_ENABLE		BIT(0)  /* this bit is NOT banked */
+#define GT_CONTROL_COMP_ENABLE		BIT(1)	/* banked */
+#define GT_CONTROL_IRQ_ENABLE		BIT(2)	/* banked */
+#define GT_CONTROL_AUTO_INC		BIT(3)	/* banked */
+
+#define GT_INT_STATUS	0x0c
+#define GT_INT_STATUS_EVENT_FLAG	BIT(0)
+
+#define GT_COMP0	0x10
+#define GT_COMP1	0x14
+#define GT_AUTO_INC	0x18
+
+/*
+ * We are expecting to be clocked by the ARM peripheral clock.
+ *
+ * Note: it is assumed we are using a prescaler value of zero, so this is
+ * the units for all operations.
+ */
+static void __iomem *gt_base;
+static unsigned long gt_clk_rate;
+static int gt_ppi;
+static struct clock_event_device __percpu *gt_evt;
+
+/*
+ * To get the value from the Global Timer Counter register proceed as follows:
+ * 1. Read the upper 32-bit timer counter register
+ * 2. Read the lower 32-bit timer counter register
+ * 3. Read the upper 32-bit timer counter register again. If the value is
+ *  different to the 32-bit upper value read previously, go back to step 2.
+ *  Otherwise the 64-bit timer counter value is correct.
+ */
+static u64 gt_counter_read(void)
+{
+	u64 counter;
+	u32 lower;
+	u32 upper, old_upper;
+
+	upper = readl_relaxed(gt_base + GT_COUNTER1);
+	do {
+		old_upper = upper;
+		lower = readl_relaxed(gt_base + GT_COUNTER0);
+		upper = readl_relaxed(gt_base + GT_COUNTER1);
+	} while (upper != old_upper);
+
+	counter = upper;
+	counter <<= 32;
+	counter |= lower;
+	return counter;
+}
+
+/**
+ * To ensure that updates to comparator value register do not set the
+ * Interrupt Status Register proceed as follows:
+ * 1. Clear the Comp Enable bit in the Timer Control Register.
+ * 2. Write the lower 32-bit Comparator Value Register.
+ * 3. Write the upper 32-bit Comparator Value Register.
+ * 4. Set the Comp Enable bit and, if necessary, the IRQ enable bit.
+ */
+static void gt_compare_set(unsigned long delta, int periodic)
+{
+	u64 counter = gt_counter_read();
+	unsigned long ctrl = readl(gt_base + GT_CONTROL);
+
+	counter += delta;
+	ctrl &=  ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE);
+
+	writel(ctrl, gt_base + GT_CONTROL);
+	writel(lower_32_bits(counter), gt_base + GT_COMP0);
+	writel(upper_32_bits(counter), gt_base + GT_COMP1);
+
+	if (periodic) {
+		writel(delta, gt_base + GT_AUTO_INC);
+		ctrl |= GT_CONTROL_AUTO_INC;
+	}
+
+	ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
+	writel(ctrl, gt_base + GT_CONTROL);
+}
+
+static void gt_clockevent_set_mode(enum clock_event_mode mode,
+				   struct clock_event_device *clk)
+{
+	unsigned long ctrl;
+
+	switch (mode) {
+	case CLOCK_EVT_MODE_PERIODIC:
+		gt_compare_set(DIV_ROUND_CLOSEST(gt_clk_rate, HZ), 1);
+		break;
+	case CLOCK_EVT_MODE_ONESHOT:
+	case CLOCK_EVT_MODE_UNUSED:
+	case CLOCK_EVT_MODE_SHUTDOWN:
+		ctrl = readl(gt_base + GT_CONTROL);
+		ctrl &= ~(GT_CONTROL_COMP_ENABLE |
+				GT_CONTROL_IRQ_ENABLE | GT_CONTROL_AUTO_INC);
+		writel(ctrl, gt_base + GT_CONTROL);
+		break;
+	default:
+		break;
+	}
+}
+
+static int gt_clockevent_set_next_event(unsigned long evt,
+					struct clock_event_device *unused)
+{
+	gt_compare_set(evt, 0);
+	return 0;
+}
+
+static irqreturn_t gt_clockevent_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+
+	if (readl_relaxed(gt_base + GT_INT_STATUS) &
+				GT_INT_STATUS_EVENT_FLAG) {
+		/**
+		 * ERRATA 740657( Global Timer can send 2 interrupts for
+		 * the same event in single-shot mode)
+		 * Workaround:
+		 *	Either disable single-shot mode.
+		 *	Or
+		 *	Modify the Interrupt Handler to avoid the
+		 *	offending sequence. This is achieved by clearing
+		 *	the Global Timer flag _after_ having incremented
+		 *	the Comparator register	value to a higher value.
+		 */
+		if (!(readl_relaxed(gt_base + GT_CONTROL) &
+						GT_CONTROL_AUTO_INC))
+			gt_compare_set(ULONG_MAX, 0);
+
+		writel_relaxed(GT_INT_STATUS_EVENT_FLAG,
+					gt_base + GT_INT_STATUS);
+
+		evt->event_handler(evt);
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+static int __cpuinit gt_clockevents_init(struct clock_event_device *clk)
+{
+	int cpu = smp_processor_id();
+
+	clk->name = "arm_global_timer";
+	clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
+	clk->set_mode = gt_clockevent_set_mode;
+	clk->set_next_event = gt_clockevent_set_next_event;
+	clk->cpumask = cpumask_of(cpu);
+	clk->irq = gt_ppi;
+	clockevents_config_and_register(clk, gt_clk_rate,
+					1, 0xffffffff);
+	enable_percpu_irq(clk->irq, IRQ_TYPE_NONE);
+	return 0;
+}
+
+static void gt_clockevents_stop(struct clock_event_device *clk)
+{
+	gt_clockevent_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
+	disable_percpu_irq(clk->irq);
+}
+
+static int __cpuinit gt_clockevents_setup(struct clock_event_device *clk)
+{
+	struct clock_event_device *evt = this_cpu_ptr(gt_evt);
+	return evt->name ? 0 : gt_clockevents_init(evt);
+}
+
+static cycle_t gt_clocksource_read(struct clocksource *cs)
+{
+	return gt_counter_read();
+}
+
+static struct clocksource gt_clocksource = {
+	.name	= "arm_global_timer",
+	.rating	= 300,
+	.read	= gt_clocksource_read,
+	.mask	= CLOCKSOURCE_MASK(64),
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
+static u32 gt_sched_clock_read(void)
+{
+	if (!gt_base)
+		return 0;
+
+	return gt_counter_read();
+}
+#endif
+
+static void __init gt_clocksource_init(void)
+{
+	writel(0, gt_base + GT_CONTROL);
+	writel(0, gt_base + GT_COUNTER0);
+	writel(0, gt_base + GT_COUNTER1);
+	/* enables timer on all the cores */
+	writel(GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL);
+
+#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
+	setup_sched_clock(gt_sched_clock_read, 32, gt_clk_rate);
+#endif
+	clocksource_register_hz(&gt_clocksource, gt_clk_rate);
+}
+
+#ifdef CONFIG_LOCAL_TIMERS
+static struct local_timer_ops gt_lt_ops __cpuinitdata = {
+	.setup	= gt_clockevents_setup,
+	.stop	= gt_clockevents_stop,
+};
+#endif
+
+static void __init global_timer_of_register(struct device_node *np)
+{
+	struct clk *gt_clk;
+	int err = 0;
+
+	/*
+	 * In r2p0 the comparators for each processor with the global timer
+	 * fire when the timer value is greater than or equal to. In previous
+	 * revisions the comparators fired when the timer value was equal to.
+	 */
+	if ((read_cpuid_id() & 0xf0000f) < 0x200000) {
+		pr_warn("global-timer: non support for this cpu version.\n");
+		return;
+	}
+
+	gt_ppi = irq_of_parse_and_map(np, 0);
+	if (!gt_ppi) {
+		pr_warn("global-timer: unable to parse irq\n");
+		return;
+	}
+
+	gt_base = of_iomap(np, 0);
+	if (!gt_base) {
+		pr_warn("global-timer: invalid base address\n");
+		return;
+	}
+
+	gt_clk = of_clk_get(np, 0);
+	if (!IS_ERR(gt_clk)) {
+		err = clk_prepare_enable(gt_clk);
+		if (err)
+			goto out_unmap;
+	} else {
+		pr_warn("global-timer: clk not found\n");
+		err = -EINVAL;
+		goto out_unmap;
+	}
+
+	gt_evt = alloc_percpu(struct clock_event_device);
+	if (!gt_evt) {
+		pr_warn("global-timer: can't allocate memory\n");
+		err = -ENOMEM;
+		goto out_clk;
+	}
+
+	err = request_percpu_irq(gt_ppi, gt_clockevent_interrupt,
+				 "gt", gt_evt);
+	if (err) {
+		pr_warn("global-timer: can't register interrupt %d (%d)\n",
+			gt_ppi, err);
+		goto out_free;
+	}
+
+	gt_clk_rate = clk_get_rate(gt_clk);
+	gt_clocksource_init();
+	gt_clockevents_init(this_cpu_ptr(gt_evt));
+
+#ifdef CONFIG_LOCAL_TIMERS
+	if (local_timer_register(&gt_lt_ops))
+		pr_warn("global-timer: unable to register local timer.\n");
+#endif
+
+	return;
+
+out_free:
+	free_percpu(gt_evt);
+out_clk:
+	clk_disable_unprepare(gt_clk);
+out_unmap:
+	iounmap(gt_base);
+	WARN(err, "ARM Global timer register failed (%d)\n", err);
+}
+
+/* Only tested on r2p2 and r3p0  */
+CLOCKSOURCE_OF_DECLARE(arm_gt, "arm,cortex-a9-global-timer",
+			global_timer_of_register);
-- 
1.7.6.5

Re: [PATCH v5] clocksource:arm_global_timer: Add ARM global timer support.

[Thomas Gleixner]

On Mon, 24 Jun 2013, Srinivas KANDAGATLA wrote:

> From: Stuart Menefy <stuart.menefy@st.com>
> 
> This is a simple driver for the global timer module found in the Cortex
> A9-MP cores from revision r1p0 onwards. This should be able to perform
> the functions of the system timer and the local timer in an SMP system.
> 
> The global timer has the following features:
>     The global timer is a 64-bit incrementing counter with an
> auto-incrementing feature. It continues incrementing after sending
> interrupts. The global timer is memory mapped in the private memory
> region.
>     The global timer is accessible to all Cortex-A9 processors in the
> cluster. Each Cortex-A9 processor has a private 64-bit comparator that
> is used to assert a private interrupt when the global timer has reached
> the comparator value. All the Cortex-A9 processors in a design use the
> banked ID, ID27, for this interrupt. ID27 is sent to the Interrupt
> Controller as a Private Peripheral Interrupt. The global timer is
> clocked by PERIPHCLK.
> 
> Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
> CC: Arnd Bergmann <arnd@arndb.de>
> CC: Rob Herring <robherring2@gmail.com>
> CC: Linus Walleij <linus.walleij@linaro.org>
> CC: Will Deacon <will.deacon@arm.com>
> CC: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

Re: [PATCH v5] clocksource:arm_global_timer: Add ARM global timer support.

[Stephen Boyd]

On 06/24/13 08:53, Srinivas KANDAGATLA wrote:
> +
> +static void gt_clockevents_stop(struct clock_event_device *clk)
> +{
> +	gt_clockevent_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
> +	disable_percpu_irq(clk->irq);
> +}
> +
> +static int __cpuinit gt_clockevents_setup(struct clock_event_device *clk)
> +{
> +	struct clock_event_device *evt = this_cpu_ptr(gt_evt);
> +	return evt->name ? 0 : gt_clockevents_init(evt);
> +}

How does this work? gt_clockevents_stop() is using the
clock_event_device struct from the ARM local timer layer whereas
gt_clockevents_setup() is using a driver private allocation. Please just
don't use the local timer API at all and use cpu notifiers instead.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

Re: [PATCH v5] clocksource:arm_global_timer: Add ARM global timer support.

[Srinivas KANDAGATLA]

On 24/06/13 21:06, Stephen Boyd wrote:
> On 06/24/13 08:53, Srinivas KANDAGATLA wrote:
>> +
>> +static void gt_clockevents_stop(struct clock_event_device *clk)
>> +{
>> +	gt_clockevent_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
>> +	disable_percpu_irq(clk->irq);
>> +}
>> +
>> +static int __cpuinit gt_clockevents_setup(struct clock_event_device *clk)
>> +{
>> +	struct clock_event_device *evt = this_cpu_ptr(gt_evt);
>> +	return evt->name ? 0 : gt_clockevents_init(evt);
>> +}
> 
> How does this work? gt_clockevents_stop() is using the
> clock_event_device struct from the ARM local timer layer whereas
> gt_clockevents_setup() is using a driver private allocation.
Thanks for pointing this..
This should fix it.

static void gt_clockevents_stop(struct clock_event_device *clk)
{
	struct clock_event_device *evt = this_cpu_ptr(gt_evt);
	gt_clockevent_set_mode(CLOCK_EVT_MODE_UNUSED, evt);
	disable_percpu_irq(evt->irq);
}

 Please just
> don't use the local timer API at all and use cpu notifiers instead.
Last time when I did try using cpu notifiers like arm_arch_timer, the
broadcast dummy timer did kick off and took over the local timer on the
secondary cpus. Resulting in lot of broadcast IPI's.

If I use cpu notifiers I will end up two clk events on a each core (one
dummy from arm/kernel/smp.c and other gt clk_evt). I think I can only
use cpu notifiers in my case once your patches are in.
Also I cant disable LOCAL_TIMERS as it y by default.

Am I missing something?

Am happy to move to cpu notifiers if it works, else the driver will be
broken.



Thanks,
srini
> 

Re: [PATCH v5] clocksource:arm_global_timer: Add ARM global timer support.

[Srinivas KANDAGATLA]

On 24/06/13 21:01, Thomas Gleixner wrote:
> On Mon, 24 Jun 2013, Srinivas KANDAGATLA wrote:
> 
>> From: Stuart Menefy <stuart.menefy@st.com>
>>
>> This is a simple driver for the global timer module found in the Cortex
>> A9-MP cores from revision r1p0 onwards. This should be able to perform
>> the functions of the system timer and the local timer in an SMP system.
>>
>> The global timer has the following features:
>>     The global timer is a 64-bit incrementing counter with an
>> auto-incrementing feature. It continues incrementing after sending
>> interrupts. The global timer is memory mapped in the private memory
>> region.
>>     The global timer is accessible to all Cortex-A9 processors in the
>> cluster. Each Cortex-A9 processor has a private 64-bit comparator that
>> is used to assert a private interrupt when the global timer has reached
>> the comparator value. All the Cortex-A9 processors in a design use the
>> banked ID, ID27, for this interrupt. ID27 is sent to the Interrupt
>> Controller as a Private Peripheral Interrupt. The global timer is
>> clocked by PERIPHCLK.
>>
>> Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
>> CC: Arnd Bergmann <arnd@arndb.de>
>> CC: Rob Herring <robherring2@gmail.com>
>> CC: Linus Walleij <linus.walleij@linaro.org>
>> CC: Will Deacon <will.deacon@arm.com>
>> CC: Thomas Gleixner <tglx@linutronix.de>
> 
> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Thanks Thomas,
I will fix Stephen's comment in next spin.

Thanks,
srini
> _______________________________________________
> devicetree-discuss mailing list
> devicetree-discuss@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/devicetree-discuss
> 

Re: [PATCH v5] clocksource:arm_global_timer: Add ARM global timer support.

[Stephen Boyd]

On 06/24/13 14:08, Srinivas KANDAGATLA wrote:
> On 24/06/13 21:06, Stephen Boyd wrote:
>> On 06/24/13 08:53, Srinivas KANDAGATLA wrote:
>>> +
>>> +static void gt_clockevents_stop(struct clock_event_device *clk)
>>> +{
>>> +	gt_clockevent_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
>>> +	disable_percpu_irq(clk->irq);
>>> +}
>>> +
>>> +static int __cpuinit gt_clockevents_setup(struct clock_event_device *clk)
>>> +{
>>> +	struct clock_event_device *evt = this_cpu_ptr(gt_evt);
>>> +	return evt->name ? 0 : gt_clockevents_init(evt);
>>> +}
>> How does this work? gt_clockevents_stop() is using the
>> clock_event_device struct from the ARM local timer layer whereas
>> gt_clockevents_setup() is using a driver private allocation.
> Thanks for pointing this..
> This should fix it.
>
> static void gt_clockevents_stop(struct clock_event_device *clk)
> {
> 	struct clock_event_device *evt = this_cpu_ptr(gt_evt);
> 	gt_clockevent_set_mode(CLOCK_EVT_MODE_UNUSED, evt);
> 	disable_percpu_irq(evt->irq);
> }

Looks good, but even better would be to not use the local timer API.

>  Please just
>> don't use the local timer API at all and use cpu notifiers instead.
> Last time when I did try using cpu notifiers like arm_arch_timer, the
> broadcast dummy timer did kick off and took over the local timer on the
> secondary cpus. Resulting in lot of broadcast IPI's.
>
> If I use cpu notifiers I will end up two clk events on a each core (one
> dummy from arm/kernel/smp.c and other gt clk_evt). I think I can only
> use cpu notifiers in my case once your patches are in.
> Also I cant disable LOCAL_TIMERS as it y by default.
>
> Am I missing something?
>
> Am happy to move to cpu notifiers if it works, else the driver will be
> broken.

I think the problem is your clockevent has no rating. Please give it a
rating (300?) so that it prevents the dummy from taking over. You don't
need to worry about disabling the local timer API, it will register a
harmless clockevent with a low rating (100) that should be ignored.

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Re: [PATCH v5] clocksource:arm_global_timer: Add ARM global timer support.

[Stephen Boyd]

On 06/24/13 08:53, Srinivas KANDAGATLA wrote:
> +#include <linux/clkdev.h>

Why do you need this include?

> +#include <asm/mach/irq.h>

And this one?

> +static u64 gt_counter_read(void)
> +{
> +	u64 counter;
> +	u32 lower;
> +	u32 upper, old_upper;
> +
> +	upper = readl_relaxed(gt_base + GT_COUNTER1);
> +	do {
> +		old_upper = upper;
> +		lower = readl_relaxed(gt_base + GT_COUNTER0);
> +		upper = readl_relaxed(gt_base + GT_COUNTER1);
[snip]
> +static void gt_compare_set(unsigned long delta, int periodic)
> +{
> +	u64 counter = gt_counter_read();
> +	unsigned long ctrl = readl(gt_base + GT_CONTROL);
> +
> +	counter += delta;
> +	ctrl &=  ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE);
> +
> +	writel(ctrl, gt_base + GT_CONTROL);
> +	writel(lower_32_bits(counter), gt_base + GT_COMP0);
> +	writel(upper_32_bits(counter), gt_base + GT_COMP1);
> +
> +	if (periodic) {
> +		writel(delta, gt_base + GT_AUTO_INC);
> +		ctrl |= GT_CONTROL_AUTO_INC;
> +	}
> +
> +	ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
> +	writel(ctrl, gt_base + GT_CONTROL);
> +}

Why is there a mix of the relaxed and non-relaxed io accessors?

> +#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
> +static u32 gt_sched_clock_read(void)

notrace

> +{
> +	if (!gt_base)
> +		return 0;

Seems impossible? Remove this check?

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Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

Re: [PATCH v5] clocksource:arm_global_timer: Add ARM global timer support.

[Srinivas KANDAGATLA]

Thankyou for the comments.
On 24/06/13 23:08, Stephen Boyd wrote:
> On 06/24/13 08:53, Srinivas KANDAGATLA wrote:
>> +#include <linux/clkdev.h>
> 
> Why do you need this include?
> 
>> +#include <asm/mach/irq.h>
> 
> And this one?
Removed them.
> 
>> +static u64 gt_counter_read(void)
>> +{
>> +	u64 counter;
>> +	u32 lower;
>> +	u32 upper, old_upper;
>> +
>> +	upper = readl_relaxed(gt_base + GT_COUNTER1);
>> +	do {
>> +		old_upper = upper;
>> +		lower = readl_relaxed(gt_base + GT_COUNTER0);
>> +		upper = readl_relaxed(gt_base + GT_COUNTER1);
> [snip]
>> +static void gt_compare_set(unsigned long delta, int periodic)
>> +{
>> +	u64 counter = gt_counter_read();
>> +	unsigned long ctrl = readl(gt_base + GT_CONTROL);
>> +
>> +	counter += delta;
>> +	ctrl &=  ~(GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE);
>> +
>> +	writel(ctrl, gt_base + GT_CONTROL);
>> +	writel(lower_32_bits(counter), gt_base + GT_COMP0);
>> +	writel(upper_32_bits(counter), gt_base + GT_COMP1);
>> +
>> +	if (periodic) {
>> +		writel(delta, gt_base + GT_AUTO_INC);
>> +		ctrl |= GT_CONTROL_AUTO_INC;
>> +	}
>> +
>> +	ctrl |= GT_CONTROL_COMP_ENABLE | GT_CONTROL_IRQ_ENABLE;
>> +	writel(ctrl, gt_base + GT_CONTROL);
>> +}
> 
> Why is there a mix of the relaxed and non-relaxed io accessors?

gt_counter_read will be used very frequently, so using relaxed can
reduce latencies involved in memory barriers.

> 
>> +#ifdef CONFIG_CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
>> +static u32 gt_sched_clock_read(void)
> 
> notrace
> 
Ok, fixed it.
>> +{
>> +	if (!gt_base)
>> +		return 0;
> 
> Seems impossible? Remove this check?
Yep, I agree this case is impossible in the code flow.
> 

Thanks,
srini

Re: [PATCH v5] clocksource:arm_global_timer: Add ARM global timer support.

[Srinivas KANDAGATLA]

Thankyou for the comments,
On 24/06/13 23:00, Stephen Boyd wrote:
> On 06/24/13 14:08, Srinivas KANDAGATLA wrote:
>> On 24/06/13 21:06, Stephen Boyd wrote:
>>> On 06/24/13 08:53, Srinivas KANDAGATLA wrote:
>
> 
> I think the problem is your clockevent has no rating. Please give it a
> rating (300?) so that it prevents the dummy from taking over. You don't
> need to worry about disabling the local timer API, it will register a
> harmless clockevent with a low rating (100) that should be ignored.
> 
I think I forgot to add rating in my last attempt to use cpu notifier.
With rating set to 300, the driver works fine with cpu notifiers.
Will send a new patch.

Thanks,
srini