[03/14] clocksource: Add ARM System timer driver
diff mbox

Message ID 1423763164-5606-4-git-send-email-mcoquelin.stm32@gmail.com
State New
Headers show

Commit Message

Maxime Coquelin Feb. 12, 2015, 5:45 p.m. UTC
This patch adds clocksource support for ARMv7-M's System timer,
also known as SysTick.

Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
---
 .../devicetree/bindings/arm/system_timer.txt       | 15 +++++
 drivers/clocksource/Kconfig                        |  7 ++
 drivers/clocksource/Makefile                       |  1 +
 drivers/clocksource/arm_system_timer.c             | 74 ++++++++++++++++++++++
 4 files changed, 97 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/arm/system_timer.txt
 create mode 100644 drivers/clocksource/arm_system_timer.c

Comments

Rob Herring Feb. 15, 2015, 10:31 p.m. UTC | #1
On Thu, Feb 12, 2015 at 11:45 AM, Maxime Coquelin
<mcoquelin.stm32@gmail.com> wrote:
> This patch adds clocksource support for ARMv7-M's System timer,
> also known as SysTick.
>
> Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
> ---
>  .../devicetree/bindings/arm/system_timer.txt       | 15 +++++

Please include v7M in the name. System timer sounds very generic. This
is the only timer architecturally defined IIRC, so perhaps just
"armv7m_systick".

>  drivers/clocksource/Kconfig                        |  7 ++
>  drivers/clocksource/Makefile                       |  1 +
>  drivers/clocksource/arm_system_timer.c             | 74 ++++++++++++++++++++++

Same here.


>  4 files changed, 97 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/system_timer.txt
>  create mode 100644 drivers/clocksource/arm_system_timer.c
>
> diff --git a/Documentation/devicetree/bindings/arm/system_timer.txt b/Documentation/devicetree/bindings/arm/system_timer.txt
> new file mode 100644
> index 0000000..35268b7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/system_timer.txt
> @@ -0,0 +1,15 @@
> +* ARM System Timer
> +
> +ARMv7-M includes a system timer, known as SysTick. Current driver only
> +implements the clocksource feature.
> +
> +Required properties:
> +- compatible : Should be "arm,armv7m-systick"
> +- reg       : The address range of the timer
> +- clocks     : The input clock of the timer

You may want to consider supporting "clock-frequency" here too. In
more simple chips you may just have fixed clocks and may want to run a
kernel with COMMON_CLK disabled for size savings.

> +
> +systick: system-timer {

This should be "systick: timer@e000e010".

Same for your dts file.

> +       compatible = "arm,armv7m-systick";
> +       reg = <0xe000e010 0x10>;
> +       clocks = <&clk_systick>;
> +};
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index fc01ec2..f9fe4ac 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -124,6 +124,13 @@ config CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
>         help
>          Use ARM global timer clock source as sched_clock
>
> +config ARM_SYSTEM_TIMER
> +       bool
> +       select CLKSRC_OF if OF
> +       select CLKSRC_MMIO
> +       help
> +         This options enables support for the ARM system timer unit
> +
>  config ATMEL_PIT
>         select CLKSRC_OF if OF
>         def_bool SOC_AT91SAM9 || SOC_SAMA5
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 94d90b2..194400b 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -42,6 +42,7 @@ obj-$(CONFIG_MTK_TIMER)               += mtk_timer.o
>
>  obj-$(CONFIG_ARM_ARCH_TIMER)           += arm_arch_timer.o
>  obj-$(CONFIG_ARM_GLOBAL_TIMER)         += arm_global_timer.o
> +obj-$(CONFIG_ARM_SYSTEM_TIMER)         += arm_system_timer.o
>  obj-$(CONFIG_CLKSRC_METAG_GENERIC)     += metag_generic.o
>  obj-$(CONFIG_ARCH_HAS_TICK_BROADCAST)  += dummy_timer.o
>  obj-$(CONFIG_ARCH_KEYSTONE)            += timer-keystone.o
> diff --git a/drivers/clocksource/arm_system_timer.c b/drivers/clocksource/arm_system_timer.c
> new file mode 100644
> index 0000000..69e6ef9
> --- /dev/null
> +++ b/drivers/clocksource/arm_system_timer.c
> @@ -0,0 +1,74 @@
> +/*
> + * Copyright (C) Maxime Coquelin 2015
> + * Author:  Maxime Coquelin <mcoquelin.stm32@gmail.com>
> + * License terms:  GNU General Public License (GPL), version 2
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/clocksource.h>
> +#include <linux/clockchips.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/clk.h>
> +#include <linux/bitops.h>
> +
> +#define SYST_CSR       0x00
> +#define SYST_RVR       0x04
> +#define SYST_CVR       0x08
> +#define SYST_CALIB     0x0c
> +
> +#define SYST_CSR_ENABLE BIT(0)
> +
> +#define SYSTICK_LOAD_RELOAD_MASK 0x00FFFFFF
> +
> +static void __init system_timer_of_register(struct device_node *np)
> +{
> +       struct clk *clk;
> +       void __iomem *base;
> +       unsigned long rate;
> +       int ret;
> +
> +       base = of_iomap(np, 0);
> +       if (!base) {
> +               pr_warn("system-timer: invalid base address\n");
> +               return;
> +       }
> +
> +       clk = of_clk_get(np, 0);
> +       if (IS_ERR(clk)) {
> +               pr_warn("system-timer: clk not found\n");
> +               ret = PTR_ERR(clk);
> +               goto out_unmap;
> +       }
> +
> +       ret = clk_prepare_enable(clk);
> +       if (ret)
> +               goto out_clk_put;
> +
> +       rate = clk_get_rate(clk);
> +
> +       writel_relaxed(SYSTICK_LOAD_RELOAD_MASK, base + SYST_RVR);
> +       writel_relaxed(SYST_CSR_ENABLE, base + SYST_CSR);
> +
> +       ret = clocksource_mmio_init(base + SYST_CVR, "arm_system_timer", rate,
> +                       200, 24, clocksource_mmio_readl_down);
> +       if (ret) {
> +               pr_err("failed to init clocksource (%d)\n", ret);
> +               goto out_clk_disable;
> +       }
> +
> +       pr_info("ARM System timer initialized as clocksource\n");
> +
> +       return;
> +
> +out_clk_disable:
> +       clk_disable_unprepare(clk);
> +out_clk_put:
> +       clk_put(clk);
> +out_unmap:
> +       iounmap(base);
> +       WARN(ret, "ARM System timer register failed (%d)\n", ret);
> +}
> +
> +CLOCKSOURCE_OF_DECLARE(arm_systick, "arm,armv7m-systick",
> +                       system_timer_of_register);
> --
> 1.9.1
>
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Andreas Färber Feb. 15, 2015, 11:43 p.m. UTC | #2
Am 12.02.2015 um 18:45 schrieb Maxime Coquelin:
> This patch adds clocksource support for ARMv7-M's System timer,
> also known as SysTick.
> 
> Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
> ---
>  .../devicetree/bindings/arm/system_timer.txt       | 15 +++++
>  drivers/clocksource/Kconfig                        |  7 ++
>  drivers/clocksource/Makefile                       |  1 +
>  drivers/clocksource/arm_system_timer.c             | 74 ++++++++++++++++++++++
>  4 files changed, 97 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/system_timer.txt
>  create mode 100644 drivers/clocksource/arm_system_timer.c
> 
> diff --git a/Documentation/devicetree/bindings/arm/system_timer.txt b/Documentation/devicetree/bindings/arm/system_timer.txt
> new file mode 100644
> index 0000000..35268b7
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/system_timer.txt
> @@ -0,0 +1,15 @@
> +* ARM System Timer
> +
> +ARMv7-M includes a system timer, known as SysTick. Current driver only
> +implements the clocksource feature.
> +
> +Required properties:
> +- compatible : Should be "arm,armv7m-systick"
> +- reg	     : The address range of the timer
> +- clocks     : The input clock of the timer
> +
> +systick: system-timer {
> +	compatible = "arm,armv7m-systick";
> +	reg = <0xe000e010 0x10>;
> +	clocks = <&clk_systick>;
> +};

Binding documentation is supposed to go into its own patch:
https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/Documentation/devicetree/bindings/submitting-patches.txt

> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index fc01ec2..f9fe4ac 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -124,6 +124,13 @@ config CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
>  	help
>  	 Use ARM global timer clock source as sched_clock
>  
> +config ARM_SYSTEM_TIMER
> +	bool
> +	select CLKSRC_OF if OF
> +	select CLKSRC_MMIO
> +	help
> +	  This options enables support for the ARM system timer unit
> +
>  config ATMEL_PIT
>  	select CLKSRC_OF if OF
>  	def_bool SOC_AT91SAM9 || SOC_SAMA5
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 94d90b2..194400b 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -42,6 +42,7 @@ obj-$(CONFIG_MTK_TIMER)		+= mtk_timer.o
>  
>  obj-$(CONFIG_ARM_ARCH_TIMER)		+= arm_arch_timer.o
>  obj-$(CONFIG_ARM_GLOBAL_TIMER)		+= arm_global_timer.o
> +obj-$(CONFIG_ARM_SYSTEM_TIMER)		+= arm_system_timer.o
>  obj-$(CONFIG_CLKSRC_METAG_GENERIC)	+= metag_generic.o
>  obj-$(CONFIG_ARCH_HAS_TICK_BROADCAST)	+= dummy_timer.o
>  obj-$(CONFIG_ARCH_KEYSTONE)		+= timer-keystone.o
> diff --git a/drivers/clocksource/arm_system_timer.c b/drivers/clocksource/arm_system_timer.c
> new file mode 100644
> index 0000000..69e6ef9
> --- /dev/null
> +++ b/drivers/clocksource/arm_system_timer.c
> @@ -0,0 +1,74 @@
> +/*
> + * Copyright (C) Maxime Coquelin 2015
> + * Author:  Maxime Coquelin <mcoquelin.stm32@gmail.com>
> + * License terms:  GNU General Public License (GPL), version 2
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/clocksource.h>
> +#include <linux/clockchips.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/clk.h>
> +#include <linux/bitops.h>
> +
> +#define SYST_CSR	0x00
> +#define SYST_RVR	0x04
> +#define SYST_CVR	0x08
> +#define SYST_CALIB	0x0c
> +
> +#define SYST_CSR_ENABLE BIT(0)
> +
> +#define SYSTICK_LOAD_RELOAD_MASK 0x00FFFFFF
> +
> +static void __init system_timer_of_register(struct device_node *np)
> +{
> +	struct clk *clk;
> +	void __iomem *base;
> +	unsigned long rate;
> +	int ret;
> +
> +	base = of_iomap(np, 0);
> +	if (!base) {
> +		pr_warn("system-timer: invalid base address\n");
> +		return;
> +	}
> +
> +	clk = of_clk_get(np, 0);
> +	if (IS_ERR(clk)) {
> +		pr_warn("system-timer: clk not found\n");
> +		ret = PTR_ERR(clk);
> +		goto out_unmap;
> +	}
> +
> +	ret = clk_prepare_enable(clk);
> +	if (ret)
> +		goto out_clk_put;
> +
> +	rate = clk_get_rate(clk);
> +
> +	writel_relaxed(SYSTICK_LOAD_RELOAD_MASK, base + SYST_RVR);
> +	writel_relaxed(SYST_CSR_ENABLE, base + SYST_CSR);
> +
> +	ret = clocksource_mmio_init(base + SYST_CVR, "arm_system_timer", rate,
> +			200, 24, clocksource_mmio_readl_down);
> +	if (ret) {
> +		pr_err("failed to init clocksource (%d)\n", ret);
> +		goto out_clk_disable;
> +	}
> +
> +	pr_info("ARM System timer initialized as clocksource\n");
> +
> +	return;
> +
> +out_clk_disable:
> +	clk_disable_unprepare(clk);
> +out_clk_put:
> +	clk_put(clk);
> +out_unmap:
> +	iounmap(base);
> +	WARN(ret, "ARM System timer register failed (%d)\n", ret);
> +}
> +
> +CLOCKSOURCE_OF_DECLARE(arm_systick, "arm,armv7m-systick",
> +			system_timer_of_register);

I've used a SysTick based implementation on my stm32 branch myself, but
looking at efm32 I got the impression that it would be better to use one
of the 32-bit TIM2/TIM5 as clocksource and the other as clockevents?

Still this implementation will be handy to have, also for other targets.

Regards,
Andreas
Maxime Coquelin Feb. 16, 2015, 12:08 p.m. UTC | #3
2015-02-15 23:31 GMT+01:00 Rob Herring <robherring2@gmail.com>:
> On Thu, Feb 12, 2015 at 11:45 AM, Maxime Coquelin
> <mcoquelin.stm32@gmail.com> wrote:
>> This patch adds clocksource support for ARMv7-M's System timer,
>> also known as SysTick.
>>
>> Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
>> ---
>>  .../devicetree/bindings/arm/system_timer.txt       | 15 +++++
>
> Please include v7M in the name. System timer sounds very generic. This
> is the only timer architecturally defined IIRC, so perhaps just
> "armv7m_systick".

Ok, let's go for "armv7m_systick".

>
>>  drivers/clocksource/Kconfig                        |  7 ++
>>  drivers/clocksource/Makefile                       |  1 +
>>  drivers/clocksource/arm_system_timer.c             | 74 ++++++++++++++++++++++
>
> Same here.

Agree, will be in the v2.

>
>
>>  4 files changed, 97 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/arm/system_timer.txt
>>  create mode 100644 drivers/clocksource/arm_system_timer.c
>>
>> diff --git a/Documentation/devicetree/bindings/arm/system_timer.txt b/Documentation/devicetree/bindings/arm/system_timer.txt
>> new file mode 100644
>> index 0000000..35268b7
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/arm/system_timer.txt
>> @@ -0,0 +1,15 @@
>> +* ARM System Timer
>> +
>> +ARMv7-M includes a system timer, known as SysTick. Current driver only
>> +implements the clocksource feature.
>> +
>> +Required properties:
>> +- compatible : Should be "arm,armv7m-systick"
>> +- reg       : The address range of the timer
>> +- clocks     : The input clock of the timer
>
> You may want to consider supporting "clock-frequency" here too. In
> more simple chips you may just have fixed clocks and may want to run a
> kernel with COMMON_CLK disabled for size savings.

Ok, I will add this option in the v2.

>
>> +
>> +systick: system-timer {
>
> This should be "systick: timer@e000e010".
>
> Same for your dts file.

Right, it will be fixed in the v2.

Thanks for the review,
Maxime
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Maxime Coquelin Feb. 16, 2015, 12:21 p.m. UTC | #4
2015-02-16 0:43 GMT+01:00 Andreas Färber <afaerber@suse.de>:
> Am 12.02.2015 um 18:45 schrieb Maxime Coquelin:
>> This patch adds clocksource support for ARMv7-M's System timer,
>> also known as SysTick.
>>
>> Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
>> ---
>>  .../devicetree/bindings/arm/system_timer.txt       | 15 +++++
>>  drivers/clocksource/Kconfig                        |  7 ++
>>  drivers/clocksource/Makefile                       |  1 +
>>  drivers/clocksource/arm_system_timer.c             | 74 ++++++++++++++++++++++
>>  4 files changed, 97 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/arm/system_timer.txt
>>  create mode 100644 drivers/clocksource/arm_system_timer.c
>>
>> diff --git a/Documentation/devicetree/bindings/arm/system_timer.txt b/Documentation/devicetree/bindings/arm/system_timer.txt
>> new file mode 100644
>> index 0000000..35268b7
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/arm/system_timer.txt
>> @@ -0,0 +1,15 @@
>> +* ARM System Timer
>> +
>> +ARMv7-M includes a system timer, known as SysTick. Current driver only
>> +implements the clocksource feature.
>> +
>> +Required properties:
>> +- compatible : Should be "arm,armv7m-systick"
>> +- reg             : The address range of the timer
>> +- clocks     : The input clock of the timer
>> +
>> +systick: system-timer {
>> +     compatible = "arm,armv7m-systick";
>> +     reg = <0xe000e010 0x10>;
>> +     clocks = <&clk_systick>;
>> +};
>
> Binding documentation is supposed to go into its own patch:
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/Documentation/devicetree/bindings/submitting-patches.txt
Ok, will change this in the v2.

>
...
>
> I've used a SysTick based implementation on my stm32 branch myself, but
> looking at efm32 I got the impression that it would be better to use one
> of the 32-bit TIM2/TIM5 as clocksource and the other as clockevents?
>
> Still this implementation will be handy to have, also for other targets.

My view is that we should use as much generic parts of the Cortex-M as possible.
Moreover, doing, that, we can keep one more IP instance under reset
with associated clock gated,
and so maybe reduce the power consumption a little (I haven't done any
measurements)

Do you see a case where it could be better to use the STM32 timers?


Thanks,
Maxime
>
> Regards,
> Andreas
>
> --
> SUSE Linux GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
> GF: Felix Imendörffer, Jane Smithard, Jennifer Guild, Dilip Upmanyu,
> Graham Norton; HRB 21284 (AG Nürnberg)
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Patch
diff mbox

diff --git a/Documentation/devicetree/bindings/arm/system_timer.txt b/Documentation/devicetree/bindings/arm/system_timer.txt
new file mode 100644
index 0000000..35268b7
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/system_timer.txt
@@ -0,0 +1,15 @@ 
+* ARM System Timer
+
+ARMv7-M includes a system timer, known as SysTick. Current driver only
+implements the clocksource feature.
+
+Required properties:
+- compatible : Should be "arm,armv7m-systick"
+- reg	     : The address range of the timer
+- clocks     : The input clock of the timer
+
+systick: system-timer {
+	compatible = "arm,armv7m-systick";
+	reg = <0xe000e010 0x10>;
+	clocks = <&clk_systick>;
+};
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index fc01ec2..f9fe4ac 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -124,6 +124,13 @@  config CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
 	help
 	 Use ARM global timer clock source as sched_clock
 
+config ARM_SYSTEM_TIMER
+	bool
+	select CLKSRC_OF if OF
+	select CLKSRC_MMIO
+	help
+	  This options enables support for the ARM system timer unit
+
 config ATMEL_PIT
 	select CLKSRC_OF if OF
 	def_bool SOC_AT91SAM9 || SOC_SAMA5
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 94d90b2..194400b 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -42,6 +42,7 @@  obj-$(CONFIG_MTK_TIMER)		+= mtk_timer.o
 
 obj-$(CONFIG_ARM_ARCH_TIMER)		+= arm_arch_timer.o
 obj-$(CONFIG_ARM_GLOBAL_TIMER)		+= arm_global_timer.o
+obj-$(CONFIG_ARM_SYSTEM_TIMER)		+= arm_system_timer.o
 obj-$(CONFIG_CLKSRC_METAG_GENERIC)	+= metag_generic.o
 obj-$(CONFIG_ARCH_HAS_TICK_BROADCAST)	+= dummy_timer.o
 obj-$(CONFIG_ARCH_KEYSTONE)		+= timer-keystone.o
diff --git a/drivers/clocksource/arm_system_timer.c b/drivers/clocksource/arm_system_timer.c
new file mode 100644
index 0000000..69e6ef9
--- /dev/null
+++ b/drivers/clocksource/arm_system_timer.c
@@ -0,0 +1,74 @@ 
+/*
+ * Copyright (C) Maxime Coquelin 2015
+ * Author:  Maxime Coquelin <mcoquelin.stm32@gmail.com>
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+
+#include <linux/kernel.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/clk.h>
+#include <linux/bitops.h>
+
+#define SYST_CSR	0x00
+#define SYST_RVR	0x04
+#define SYST_CVR	0x08
+#define SYST_CALIB	0x0c
+
+#define SYST_CSR_ENABLE BIT(0)
+
+#define SYSTICK_LOAD_RELOAD_MASK 0x00FFFFFF
+
+static void __init system_timer_of_register(struct device_node *np)
+{
+	struct clk *clk;
+	void __iomem *base;
+	unsigned long rate;
+	int ret;
+
+	base = of_iomap(np, 0);
+	if (!base) {
+		pr_warn("system-timer: invalid base address\n");
+		return;
+	}
+
+	clk = of_clk_get(np, 0);
+	if (IS_ERR(clk)) {
+		pr_warn("system-timer: clk not found\n");
+		ret = PTR_ERR(clk);
+		goto out_unmap;
+	}
+
+	ret = clk_prepare_enable(clk);
+	if (ret)
+		goto out_clk_put;
+
+	rate = clk_get_rate(clk);
+
+	writel_relaxed(SYSTICK_LOAD_RELOAD_MASK, base + SYST_RVR);
+	writel_relaxed(SYST_CSR_ENABLE, base + SYST_CSR);
+
+	ret = clocksource_mmio_init(base + SYST_CVR, "arm_system_timer", rate,
+			200, 24, clocksource_mmio_readl_down);
+	if (ret) {
+		pr_err("failed to init clocksource (%d)\n", ret);
+		goto out_clk_disable;
+	}
+
+	pr_info("ARM System timer initialized as clocksource\n");
+
+	return;
+
+out_clk_disable:
+	clk_disable_unprepare(clk);
+out_clk_put:
+	clk_put(clk);
+out_unmap:
+	iounmap(base);
+	WARN(ret, "ARM System timer register failed (%d)\n", ret);
+}
+
+CLOCKSOURCE_OF_DECLARE(arm_systick, "arm,armv7m-systick",
+			system_timer_of_register);