[v2,3/6] clocksource: exynos_mct: Add arch_timer cooperation mode for ARM64

Message ID 20181015123112.9379-4-m.szyprowski@samsung.com
State New
Headers show
Series
  • Proper arch timer support for Exynos5433-based TM2(e) boards
Related show

Commit Message

Marek Szyprowski Oct. 15, 2018, 12:31 p.m.
To get ARM Architected Timers working on Samsung Exynos SoCs, one has to
first configure and enable Exynos Multi-Core Timer, because they both
share some common hardware blocks. This patch adds a mode of cooperation
with arch_timer driver, so kernel can use CP15 based timer interface via
arch_timer driver, which is mandatory on ARM64. In such mode driver only
configures MCT registers and starts the timer but don't register any
clocksource or events in the system. Those are left to be handled by
arch_timer driver.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

---
 drivers/clocksource/exynos_mct.c | 52 +++++++++++++++++++++-----------
 1 file changed, 35 insertions(+), 17 deletions(-)

-- 
2.17.1

Comments

Mark Rutland Oct. 15, 2018, 1:26 p.m. | #1
On Mon, Oct 15, 2018 at 02:31:09PM +0200, Marek Szyprowski wrote:
> To get ARM Architected Timers working on Samsung Exynos SoCs, one has to

> first configure and enable Exynos Multi-Core Timer, because they both

> share some common hardware blocks.


Could you please elaborate on what exactly is shared with the MCT?

Architecturally, the OS shouldn't have to do anything to put the timers
into a usable state. All instances should be fed (directly) from the
system counter, which FW is tasked with configuring and enabling, and
all other state is private to the instance.

If we have to poke things to make them usable, that means we can't
assume that it's always safe to use the timers or counters, as the
architecture lets us, and I'd like to understand what the impact is.

e.g. does this mean that there are windows where the counters don't
tick?

Are all the counters fed the same underlying counter value? ... or are
those independent?

Thanks,
Mark.

> This patch adds a mode of cooperation with arch_timer driver, so

> kernel can use CP15 based timer interface via arch_timer driver, which

> is mandatory on ARM64. In such mode driver only configures MCT

> registers and starts the timer but don't register any clocksource or

> events in the system. Those are left to be handled by arch_timer

> driver.

> 

> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---

>  drivers/clocksource/exynos_mct.c | 52 +++++++++++++++++++++-----------

>  1 file changed, 35 insertions(+), 17 deletions(-)

> 

> diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c

> index a379f11fad2d..06cd30a6d59a 100644

> --- a/drivers/clocksource/exynos_mct.c

> +++ b/drivers/clocksource/exynos_mct.c

> @@ -57,6 +57,7 @@

>  #define TICK_BASE_CNT	1

>  

>  enum {

> +	MCT_INT_NONE = 0,

>  	MCT_INT_SPI,

>  	MCT_INT_PPI

>  };

> @@ -238,6 +239,9 @@ static int __init exynos4_clocksource_init(void)

>  {

>  	exynos4_mct_frc_start();

>  

> +	if (!mct_int_type)

> +		return 0;

> +

>  #if defined(CONFIG_ARM)

>  	exynos4_delay_timer.read_current_timer = &exynos4_read_current_timer;

>  	exynos4_delay_timer.freq = clk_rate;

> @@ -343,6 +347,9 @@ static struct irqaction mct_comp_event_irq = {

>  

>  static int exynos4_clockevent_init(void)

>  {

> +	if (!mct_int_type)

> +		return 0;

> +

>  	mct_comp_device.cpumask = cpumask_of(0);

>  	clockevents_config_and_register(&mct_comp_device, clk_rate,

>  					0xf, 0xffffffff);

> @@ -476,12 +483,12 @@ static int exynos4_mct_starting_cpu(unsigned int cpu)

>  

>  		irq_force_affinity(evt->irq, cpumask_of(cpu));

>  		enable_irq(evt->irq);

> -	} else {

> +	} else if (mct_int_type == MCT_INT_PPI) {

>  		enable_percpu_irq(mct_irqs[MCT_L0_IRQ], 0);

>  	}

> -	clockevents_config_and_register(evt, clk_rate / (TICK_BASE_CNT + 1),

> -					0xf, 0x7fffffff);

> -

> +	if (mct_int_type)

> +		clockevents_config_and_register(evt,

> +			       clk_rate / (TICK_BASE_CNT + 1), 0xf, 0x7fffffff);

>  	return 0;

>  }

>  

> @@ -496,7 +503,7 @@ static int exynos4_mct_dying_cpu(unsigned int cpu)

>  		if (evt->irq != -1)

>  			disable_irq_nosync(evt->irq);

>  		exynos4_mct_write(0x1, mevt->base + MCT_L_INT_CSTAT_OFFSET);

> -	} else {

> +	} else if (mct_int_type == MCT_INT_PPI) {

>  		disable_percpu_irq(mct_irqs[MCT_L0_IRQ]);

>  	}

>  	return 0;

> @@ -529,7 +536,7 @@ static int __init exynos4_timer_resources(struct device_node *np, void __iomem *

>  					 &percpu_mct_tick);

>  		WARN(err, "MCT: can't request IRQ %d (%d)\n",

>  		     mct_irqs[MCT_L0_IRQ], err);

> -	} else {

> +	} else if (mct_int_type == MCT_INT_SPI) {

>  		for_each_possible_cpu(cpu) {

>  			int mct_irq = mct_irqs[MCT_L0_IRQ + cpu];

>  			struct mct_clock_event_device *pcpu_mevt =

> @@ -564,7 +571,7 @@ static int __init exynos4_timer_resources(struct device_node *np, void __iomem *

>  out_irq:

>  	if (mct_int_type == MCT_INT_PPI) {

>  		free_percpu_irq(mct_irqs[MCT_L0_IRQ], &percpu_mct_tick);

> -	} else {

> +	} else if (mct_int_type == MCT_INT_SPI) {

>  		for_each_possible_cpu(cpu) {

>  			struct mct_clock_event_device *pcpu_mevt =

>  				per_cpu_ptr(&percpu_mct_tick, cpu);

> @@ -585,17 +592,28 @@ static int __init mct_init_dt(struct device_node *np, unsigned int int_type)

>  

>  	mct_int_type = int_type;

>  

> -	/* This driver uses only one global timer interrupt */

> -	mct_irqs[MCT_G0_IRQ] = irq_of_parse_and_map(np, MCT_G0_IRQ);

> +	if (IS_ENABLED(CONFIG_ARM64) && IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) {

> +		struct device_node *np = of_find_compatible_node(NULL, NULL,

> +							     "arm,armv8-timer");

> +		if (np) {

> +			mct_int_type = MCT_INT_NONE;

> +			of_node_put(np);

> +		}

> +	}

>  

> -	/*

> -	 * Find out the number of local irqs specified. The local

> -	 * timer irqs are specified after the four global timer

> -	 * irqs are specified.

> -	 */

> -	nr_irqs = of_irq_count(np);

> -	for (i = MCT_L0_IRQ; i < nr_irqs; i++)

> -		mct_irqs[i] = irq_of_parse_and_map(np, i);

> +	if (mct_int_type) {

> +		/* This driver uses only one global timer interrupt */

> +		mct_irqs[MCT_G0_IRQ] = irq_of_parse_and_map(np, MCT_G0_IRQ);

> +

> +		/*

> +		 * Find out the number of local irqs specified. The local

> +		 * timer irqs are specified after the four global timer

> +		 * irqs are specified.

> +		 */

> +		nr_irqs = of_irq_count(np);

> +		for (i = MCT_L0_IRQ; i < nr_irqs; i++)

> +			mct_irqs[i] = irq_of_parse_and_map(np, i);

> +	}

>  

>  	ret = exynos4_timer_resources(np, of_iomap(np, 0));

>  	if (ret)

> -- 

> 2.17.1

>
Krzysztof Kozlowski Oct. 16, 2018, 1:11 p.m. | #2
On Mon, 15 Oct 2018 at 14:31, Marek Szyprowski <m.szyprowski@samsung.com> wrote:
>

> To get ARM Architected Timers working on Samsung Exynos SoCs, one has to

> first configure and enable Exynos Multi-Core Timer, because they both

> share some common hardware blocks. This patch adds a mode of cooperation

> with arch_timer driver, so kernel can use CP15 based timer interface via

> arch_timer driver, which is mandatory on ARM64. In such mode driver only

> configures MCT registers and starts the timer but don't register any

> clocksource or events in the system. Those are left to be handled by

> arch_timer driver.

>

> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---

>  drivers/clocksource/exynos_mct.c | 52 +++++++++++++++++++++-----------

>  1 file changed, 35 insertions(+), 17 deletions(-)


Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>


Best regards,
Krzysztof
Chanwoo Choi Oct. 17, 2018, 5 a.m. | #3
Hi Marek,

I tested it about kernel booting and CPU hotplug through sysfs path 
on ARM64 Exynos5433-based TM2 board. It is well working.

Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>

Tested-by: Chanwoo Choi <cw00.choi@samsung.com>


But,
I have a minor comment for code clean-up.
On exynos4_mct_starting_cpu() function, the initialization of 'evt' instance
are not mandatory because 'evt' instance is not registered
by clockevents_config_and_register(). 


On 2018년 10월 15일 21:31, Marek Szyprowski wrote:
> To get ARM Architected Timers working on Samsung Exynos SoCs, one has to

> first configure and enable Exynos Multi-Core Timer, because they both

> share some common hardware blocks. This patch adds a mode of cooperation

> with arch_timer driver, so kernel can use CP15 based timer interface via

> arch_timer driver, which is mandatory on ARM64. In such mode driver only

> configures MCT registers and starts the timer but don't register any

> clocksource or events in the system. Those are left to be handled by

> arch_timer driver.

> 

> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---

>  drivers/clocksource/exynos_mct.c | 52 +++++++++++++++++++++-----------

>  1 file changed, 35 insertions(+), 17 deletions(-)

> 

> diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c

> index a379f11fad2d..06cd30a6d59a 100644

> --- a/drivers/clocksource/exynos_mct.c

> +++ b/drivers/clocksource/exynos_mct.c

> @@ -57,6 +57,7 @@

>  #define TICK_BASE_CNT	1

>  

>  enum {

> +	MCT_INT_NONE = 0,

>  	MCT_INT_SPI,

>  	MCT_INT_PPI

>  };

> @@ -238,6 +239,9 @@ static int __init exynos4_clocksource_init(void)

>  {

>  	exynos4_mct_frc_start();

>  

> +	if (!mct_int_type)

> +		return 0;

> +

>  #if defined(CONFIG_ARM)

>  	exynos4_delay_timer.read_current_timer = &exynos4_read_current_timer;

>  	exynos4_delay_timer.freq = clk_rate;

> @@ -343,6 +347,9 @@ static struct irqaction mct_comp_event_irq = {

>  

>  static int exynos4_clockevent_init(void)

>  {

> +	if (!mct_int_type)

> +		return 0;

> +

>  	mct_comp_device.cpumask = cpumask_of(0);

>  	clockevents_config_and_register(&mct_comp_device, clk_rate,

>  					0xf, 0xffffffff);

> @@ -476,12 +483,12 @@ static int exynos4_mct_starting_cpu(unsigned int cpu)

>  

>  		irq_force_affinity(evt->irq, cpumask_of(cpu));

>  		enable_irq(evt->irq);

> -	} else {

> +	} else if (mct_int_type == MCT_INT_PPI) {

>  		enable_percpu_irq(mct_irqs[MCT_L0_IRQ], 0);

>  	}

> -	clockevents_config_and_register(evt, clk_rate / (TICK_BASE_CNT + 1),

> -					0xf, 0x7fffffff);

> -

> +	if (mct_int_type)

> +		clockevents_config_and_register(evt,

> +			       clk_rate / (TICK_BASE_CNT + 1), 0xf, 0x7fffffff);

>  	return 0;

>  }

>  

> @@ -496,7 +503,7 @@ static int exynos4_mct_dying_cpu(unsigned int cpu)

>  		if (evt->irq != -1)

>  			disable_irq_nosync(evt->irq);

>  		exynos4_mct_write(0x1, mevt->base + MCT_L_INT_CSTAT_OFFSET);

> -	} else {

> +	} else if (mct_int_type == MCT_INT_PPI) {

>  		disable_percpu_irq(mct_irqs[MCT_L0_IRQ]);

>  	}

>  	return 0;

> @@ -529,7 +536,7 @@ static int __init exynos4_timer_resources(struct device_node *np, void __iomem *

>  					 &percpu_mct_tick);

>  		WARN(err, "MCT: can't request IRQ %d (%d)\n",

>  		     mct_irqs[MCT_L0_IRQ], err);

> -	} else {

> +	} else if (mct_int_type == MCT_INT_SPI) {

>  		for_each_possible_cpu(cpu) {

>  			int mct_irq = mct_irqs[MCT_L0_IRQ + cpu];

>  			struct mct_clock_event_device *pcpu_mevt =

> @@ -564,7 +571,7 @@ static int __init exynos4_timer_resources(struct device_node *np, void __iomem *

>  out_irq:

>  	if (mct_int_type == MCT_INT_PPI) {

>  		free_percpu_irq(mct_irqs[MCT_L0_IRQ], &percpu_mct_tick);

> -	} else {

> +	} else if (mct_int_type == MCT_INT_SPI) {

>  		for_each_possible_cpu(cpu) {

>  			struct mct_clock_event_device *pcpu_mevt =

>  				per_cpu_ptr(&percpu_mct_tick, cpu);

> @@ -585,17 +592,28 @@ static int __init mct_init_dt(struct device_node *np, unsigned int int_type)

>  

>  	mct_int_type = int_type;

>  

> -	/* This driver uses only one global timer interrupt */

> -	mct_irqs[MCT_G0_IRQ] = irq_of_parse_and_map(np, MCT_G0_IRQ);

> +	if (IS_ENABLED(CONFIG_ARM64) && IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) {

> +		struct device_node *np = of_find_compatible_node(NULL, NULL,

> +							     "arm,armv8-timer");

> +		if (np) {

> +			mct_int_type = MCT_INT_NONE;

> +			of_node_put(np);

> +		}

> +	}

>  

> -	/*

> -	 * Find out the number of local irqs specified. The local

> -	 * timer irqs are specified after the four global timer

> -	 * irqs are specified.

> -	 */

> -	nr_irqs = of_irq_count(np);

> -	for (i = MCT_L0_IRQ; i < nr_irqs; i++)

> -		mct_irqs[i] = irq_of_parse_and_map(np, i);

> +	if (mct_int_type) {

> +		/* This driver uses only one global timer interrupt */

> +		mct_irqs[MCT_G0_IRQ] = irq_of_parse_and_map(np, MCT_G0_IRQ);

> +

> +		/*

> +		 * Find out the number of local irqs specified. The local

> +		 * timer irqs are specified after the four global timer

> +		 * irqs are specified.

> +		 */

> +		nr_irqs = of_irq_count(np);

> +		for (i = MCT_L0_IRQ; i < nr_irqs; i++)

> +			mct_irqs[i] = irq_of_parse_and_map(np, i);

> +	}

>  

>  	ret = exynos4_timer_resources(np, of_iomap(np, 0));

>  	if (ret)

> 



-- 
Best Regards,
Chanwoo Choi
Samsung Electronics
Marek Szyprowski Oct. 17, 2018, 12:36 p.m. | #4
Hi Mark,

On 2018-10-15 15:26, Mark Rutland wrote:
> On Mon, Oct 15, 2018 at 02:31:09PM +0200, Marek Szyprowski wrote:

>> To get ARM Architected Timers working on Samsung Exynos SoCs, one has to

>> first configure and enable Exynos Multi-Core Timer, because they both

>> share some common hardware blocks.

> Could you please elaborate on what exactly is shared with the MCT?

>

> Architecturally, the OS shouldn't have to do anything to put the timers

> into a usable state. All instances should be fed (directly) from the

> system counter, which FW is tasked with configuring and enabling, and

> all other state is private to the instance.

>

> If we have to poke things to make them usable, that means we can't

> assume that it's always safe to use the timers or counters, as the

> architecture lets us, and I'd like to understand what the impact is.

>

> e.g. does this mean that there are windows where the counters don't

> tick?


Good question is always a helpful advice. I don't have such hardware
details and I've did my patches basing on what I've observed while
playing with the hardware.

I've checked again and I found that the only things that need to be
done to get ARM arch timer working are:

1. enable multi core timer clock,
2. set MCT_G_TCON_START (Timer enable) bit in MCT_G_TCON (Global timer
control) register.

Otherwise arch timer doesn't get any tick.

Changing CPUHP priorities nor any other MCT register writes are not
needed. It looks that they were leftovers from my older approaches
and I've kept them without really checking if they are needed in the
final version.

I will send a new simplified version of this patchset then.

> Are all the counters fed the same underlying counter value? ... or are

> those independent?


My summary above suggests that ARM architected timers are fed from the
physical counter, which is controlled by MCT registers.

> ...


Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Patch

diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
index a379f11fad2d..06cd30a6d59a 100644
--- a/drivers/clocksource/exynos_mct.c
+++ b/drivers/clocksource/exynos_mct.c
@@ -57,6 +57,7 @@ 
 #define TICK_BASE_CNT	1
 
 enum {
+	MCT_INT_NONE = 0,
 	MCT_INT_SPI,
 	MCT_INT_PPI
 };
@@ -238,6 +239,9 @@  static int __init exynos4_clocksource_init(void)
 {
 	exynos4_mct_frc_start();
 
+	if (!mct_int_type)
+		return 0;
+
 #if defined(CONFIG_ARM)
 	exynos4_delay_timer.read_current_timer = &exynos4_read_current_timer;
 	exynos4_delay_timer.freq = clk_rate;
@@ -343,6 +347,9 @@  static struct irqaction mct_comp_event_irq = {
 
 static int exynos4_clockevent_init(void)
 {
+	if (!mct_int_type)
+		return 0;
+
 	mct_comp_device.cpumask = cpumask_of(0);
 	clockevents_config_and_register(&mct_comp_device, clk_rate,
 					0xf, 0xffffffff);
@@ -476,12 +483,12 @@  static int exynos4_mct_starting_cpu(unsigned int cpu)
 
 		irq_force_affinity(evt->irq, cpumask_of(cpu));
 		enable_irq(evt->irq);
-	} else {
+	} else if (mct_int_type == MCT_INT_PPI) {
 		enable_percpu_irq(mct_irqs[MCT_L0_IRQ], 0);
 	}
-	clockevents_config_and_register(evt, clk_rate / (TICK_BASE_CNT + 1),
-					0xf, 0x7fffffff);
-
+	if (mct_int_type)
+		clockevents_config_and_register(evt,
+			       clk_rate / (TICK_BASE_CNT + 1), 0xf, 0x7fffffff);
 	return 0;
 }
 
@@ -496,7 +503,7 @@  static int exynos4_mct_dying_cpu(unsigned int cpu)
 		if (evt->irq != -1)
 			disable_irq_nosync(evt->irq);
 		exynos4_mct_write(0x1, mevt->base + MCT_L_INT_CSTAT_OFFSET);
-	} else {
+	} else if (mct_int_type == MCT_INT_PPI) {
 		disable_percpu_irq(mct_irqs[MCT_L0_IRQ]);
 	}
 	return 0;
@@ -529,7 +536,7 @@  static int __init exynos4_timer_resources(struct device_node *np, void __iomem *
 					 &percpu_mct_tick);
 		WARN(err, "MCT: can't request IRQ %d (%d)\n",
 		     mct_irqs[MCT_L0_IRQ], err);
-	} else {
+	} else if (mct_int_type == MCT_INT_SPI) {
 		for_each_possible_cpu(cpu) {
 			int mct_irq = mct_irqs[MCT_L0_IRQ + cpu];
 			struct mct_clock_event_device *pcpu_mevt =
@@ -564,7 +571,7 @@  static int __init exynos4_timer_resources(struct device_node *np, void __iomem *
 out_irq:
 	if (mct_int_type == MCT_INT_PPI) {
 		free_percpu_irq(mct_irqs[MCT_L0_IRQ], &percpu_mct_tick);
-	} else {
+	} else if (mct_int_type == MCT_INT_SPI) {
 		for_each_possible_cpu(cpu) {
 			struct mct_clock_event_device *pcpu_mevt =
 				per_cpu_ptr(&percpu_mct_tick, cpu);
@@ -585,17 +592,28 @@  static int __init mct_init_dt(struct device_node *np, unsigned int int_type)
 
 	mct_int_type = int_type;
 
-	/* This driver uses only one global timer interrupt */
-	mct_irqs[MCT_G0_IRQ] = irq_of_parse_and_map(np, MCT_G0_IRQ);
+	if (IS_ENABLED(CONFIG_ARM64) && IS_ENABLED(CONFIG_ARM_ARCH_TIMER)) {
+		struct device_node *np = of_find_compatible_node(NULL, NULL,
+							     "arm,armv8-timer");
+		if (np) {
+			mct_int_type = MCT_INT_NONE;
+			of_node_put(np);
+		}
+	}
 
-	/*
-	 * Find out the number of local irqs specified. The local
-	 * timer irqs are specified after the four global timer
-	 * irqs are specified.
-	 */
-	nr_irqs = of_irq_count(np);
-	for (i = MCT_L0_IRQ; i < nr_irqs; i++)
-		mct_irqs[i] = irq_of_parse_and_map(np, i);
+	if (mct_int_type) {
+		/* This driver uses only one global timer interrupt */
+		mct_irqs[MCT_G0_IRQ] = irq_of_parse_and_map(np, MCT_G0_IRQ);
+
+		/*
+		 * Find out the number of local irqs specified. The local
+		 * timer irqs are specified after the four global timer
+		 * irqs are specified.
+		 */
+		nr_irqs = of_irq_count(np);
+		for (i = MCT_L0_IRQ; i < nr_irqs; i++)
+			mct_irqs[i] = irq_of_parse_and_map(np, i);
+	}
 
 	ret = exynos4_timer_resources(np, of_iomap(np, 0));
 	if (ret)