[PATCH v2 2/2] ARM: am335x: Changed timer

[PATCH v2 2/2] ARM: am335x: Changed timer

[Daniel Schultz]

The dmtimer0 is too inaccurate to be used for measurements.
We switch to the more accurate dmtimer2.

Signed-off-by: Daniel Schultz <d.schultz@phytec.de>
---

 Changes:
	v2:
	- renamed dmtimer2.c in dmtimer.c
	- moved base address defines to global variable

 arch/arm/mach-omap/Kconfig                       |  4 +-
 arch/arm/mach-omap/Makefile                      |  2 +-
 arch/arm/mach-omap/dmtimer.c                     | 91 ++++++++++++++++++++++++
 arch/arm/mach-omap/dmtimer0.c                    | 85 ----------------------
 arch/arm/mach-omap/include/mach/am33xx-silicon.h |  3 +
 5 files changed, 97 insertions(+), 88 deletions(-)
 create mode 100644 arch/arm/mach-omap/dmtimer.c
 delete mode 100644 arch/arm/mach-omap/dmtimer0.c

diff --git a/arch/arm/mach-omap/Kconfig b/arch/arm/mach-omap/Kconfig
index af35975..87e8d44 100644
--- a/arch/arm/mach-omap/Kconfig
+++ b/arch/arm/mach-omap/Kconfig
@@ -43,7 +43,7 @@ config ARCH_AM33XX
 	select CPU_V7
 	select GENERIC_GPIO
 	select OFTREE
-	select OMAP_CLOCK_SOURCE_DMTIMER0
+	select OMAP_CLOCK_SOURCE_DMTIMER
 	help
 	  Say Y here if you are using Texas Instrument's AM33xx based platform
 
@@ -51,7 +51,7 @@ config ARCH_AM33XX
 config OMAP_CLOCK_SOURCE_S32K
 	bool
 
-config OMAP_CLOCK_SOURCE_DMTIMER0
+config OMAP_CLOCK_SOURCE_DMTIMER
 	bool
 
 config OMAP_GPMC
diff --git a/arch/arm/mach-omap/Makefile b/arch/arm/mach-omap/Makefile
index 65072b9..db2856d 100644
--- a/arch/arm/mach-omap/Makefile
+++ b/arch/arm/mach-omap/Makefile
@@ -18,7 +18,7 @@
 obj-$(CONFIG_ARCH_OMAP) += syslib.o omap_devices.o omap_generic.o omap_fb.o
 pbl-$(CONFIG_ARCH_OMAP) += syslib.o
 obj-$(CONFIG_OMAP_CLOCK_SOURCE_S32K) += s32k_clksource.o
-obj-$(CONFIG_OMAP_CLOCK_SOURCE_DMTIMER0) += dmtimer0.o
+obj-$(CONFIG_OMAP_CLOCK_SOURCE_DMTIMER) += dmtimer.o
 obj-$(CONFIG_ARCH_OMAP3) += omap3_generic.o auxcr.o
 pbl-$(CONFIG_ARCH_OMAP3) += omap3_generic.o auxcr.o
 obj-$(CONFIG_ARCH_OMAP4) += omap4_generic.o omap4_clock.o
diff --git a/arch/arm/mach-omap/dmtimer.c b/arch/arm/mach-omap/dmtimer.c
new file mode 100644
index 0000000..81978a8
--- /dev/null
+++ b/arch/arm/mach-omap/dmtimer.c
@@ -0,0 +1,91 @@
+/**
+ * @file
+ * @brief Support DMTimer counter
+ *
+ * FileName: arch/arm/mach-omap/dmtimer.c
+ */
+/*
+ * This File is based on arch/arm/mach-omap/s32k_clksource.c
+ * (C) Copyright 2008
+ * Texas Instruments, <www.ti.com>
+ * Nishanth Menon <x0nishan@ti.com>
+ *
+ * (C) Copyright 2012 Phytec Messtechnik GmbH
+ * Author: Teresa Gámez <t.gamez@phytec.de>
+ * (C) Copyright 2015 Phytec Messtechnik GmbH
+ * Author: Daniel Schultz <d.schultz@phytec.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <clock.h>
+#include <init.h>
+#include <io.h>
+#include <mach/am33xx-silicon.h>
+
+#define CLK_RC32K	32768
+#define CLK_M_OSC	25000000
+
+#define TIDR			0x0
+#define TIOCP_CFG		0x10
+#define IRQ_EOI			0x20
+#define IRQSTATUS_RAW		0x24
+#define IRQSTATUS		0x28
+#define IRQSTATUS_SET		0x2c
+#define IRQSTATUS_CLR		0x30
+#define IRQWAKEEN		0x34
+#define TCLR			0x38
+#define TCRR			0x3C
+#define TLDR			0x40
+#define TTGR			0x44
+#define TWPS			0x48
+#define TMAR			0x4C
+#define TCAR1			0x50
+#define TSICR			0x54
+#define TCAR2			0x58
+
+static void *base = (void *)AM33XX_DMTIMER2_BASE;
+
+/**
+ * @brief Provide a simple counter read
+ *
+ * @return DMTimer counter
+ */
+static uint64_t dmtimer_read(void)
+{
+	return readl(base + TCRR);
+}
+
+static struct clocksource dmtimer_cs = {
+	.read	= dmtimer_read,
+	.mask	= CLOCKSOURCE_MASK(32),
+	.shift	= 10,
+};
+
+/**
+ * @brief Initialize the Clock
+ *
+ * Enable dmtimer.
+ *
+ * @return result of @ref init_clock
+ */
+static int dmtimer_init(void)
+{
+	dmtimer_cs.mult = clocksource_hz2mult(CLK_M_OSC, dmtimer_cs.shift);
+	/* Enable counter */
+	writel(0x3, base + TCLR);
+
+	return init_clock(&dmtimer_cs);
+}
+
+/* Run me at boot time */
+core_initcall(dmtimer_init);
diff --git a/arch/arm/mach-omap/dmtimer0.c b/arch/arm/mach-omap/dmtimer0.c
deleted file mode 100644
index e536f8d..0000000
--- a/arch/arm/mach-omap/dmtimer0.c
+++ /dev/null
@@ -1,85 +0,0 @@
-/**
- * @file
- * @brief Support DMTimer0 counter
- *
- * FileName: arch/arm/mach-omap/dmtimer0.c
- */
-/*
- * This File is based on arch/arm/mach-omap/s32k_clksource.c
- * (C) Copyright 2008
- * Texas Instruments, <www.ti.com>
- * Nishanth Menon <x0nishan@ti.com>
- *
- * (C) Copyright 2012 Teresa Gámez, Phytec Messtechnik GmbH
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of
- * the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- */
-
-#include <clock.h>
-#include <init.h>
-#include <io.h>
-#include <mach/am33xx-silicon.h>
-
-#define CLK_RC32K	32768
-
-#define TIDR			0x0
-#define TIOCP_CFG		0x10
-#define IRQ_EOI			0x20
-#define IRQSTATUS_RAW		0x24
-#define IRQSTATUS		0x28
-#define IRQSTATUS_SET		0x2c
-#define IRQSTATUS_CLR		0x30
-#define IRQWAKEEN		0x34
-#define TCLR			0x38
-#define TCRR			0x3C
-#define TLDR			0x40
-#define TTGR			0x44
-#define TWPS			0x48
-#define TMAR			0x4C
-#define TCAR1			0x50
-#define TSICR			0x54
-#define TCAR2			0x58
-
-/**
- * @brief Provide a simple counter read
- *
- * @return DMTimer0 counter
- */
-static uint64_t dmtimer0_read(void)
-{
-	return readl(AM33XX_DMTIMER0_BASE + TCRR);
-}
-
-static struct clocksource dmtimer0_cs = {
-	.read	= dmtimer0_read,
-	.mask	= CLOCKSOURCE_MASK(32),
-	.shift	= 10,
-};
-
-/**
- * @brief Initialize the Clock
- *
- * Enable dmtimer0.
- *
- * @return result of @ref init_clock
- */
-static int dmtimer0_init(void)
-{
-	dmtimer0_cs.mult = clocksource_hz2mult(CLK_RC32K, dmtimer0_cs.shift);
-	/* Enable counter */
-	writel(0x3, AM33XX_DMTIMER0_BASE + TCLR);
-
-	return init_clock(&dmtimer0_cs);
-}
-
-/* Run me at boot time */
-core_initcall(dmtimer0_init);
diff --git a/arch/arm/mach-omap/include/mach/am33xx-silicon.h b/arch/arm/mach-omap/include/mach/am33xx-silicon.h
index 7c209ec..ee0b846 100644
--- a/arch/arm/mach-omap/include/mach/am33xx-silicon.h
+++ b/arch/arm/mach-omap/include/mach/am33xx-silicon.h
@@ -62,6 +62,9 @@
 
 /* DTMTimer0 */
 #define AM33XX_DMTIMER0_BASE		(AM33XX_L4_WKUP_BASE + 0x205000)
+/* DMTIimer2 */
+#define AM33XX_DMTIMER2_BASE		(AM33XX_L4_PER_BASE + 0x40000)
+#define AM33XX_CM_DPLL			(AM33XX_L4_WKUP_BASE + 0x200500)
 
 /* PRM */
 #define AM33XX_PRM_BASE			(AM33XX_L4_WKUP_BASE + 0x200000)
-- 
1.9.1


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Re: [PATCH v2 2/2] ARM: am335x: Changed timer

[Jan Lübbe]

On Do, 2015-07-16 at 10:51 +0200, Daniel Schultz wrote:
> The dmtimer0 is too inaccurate to be used for measurements.
> We switch to the more accurate dmtimer2.

What are you trying to measure? Is the resolution or the accuracy too
low?

> +#define CLK_M_OSC	25000000

> +static int dmtimer_init(void)
> +{
> +	dmtimer_cs.mult = clocksource_hz2mult(CLK_M_OSC, dmtimer_cs.shift);
> +	/* Enable counter */
> +	writel(0x3, base + TCLR);
> +
> +	return init_clock(&dmtimer_cs);

You use a fixed M_OSC of 25 MHz, but this value actually depends on the
the board. The AM335x supports 19.2, 24 and 26 MHz in addition to 25
MHz.

The advantage of using dmtimer0 is that it is always available and runs
at 32KiHz on every board.

Regards,
Jan
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Re: [PATCH v2 2/2] ARM: am335x: Changed timer

[Daniel Schultz]

Am 17.07.2015 um 11:16 schrieb Jan Lübbe:
> On Do, 2015-07-16 at 10:51 +0200, Daniel Schultz wrote:
>> The dmtimer0 is too inaccurate to be used for measurements.
>> We switch to the more accurate dmtimer2.
>
> What are you trying to measure? Is the resolution or the accuracy too
> low?
While testing with dhrystone on our boards, I figured out that the 
timestamps from dmtimer0 run 20% too quick.

You can also make a quick test on a am335x board with
sleep 10

You will notice that the sleep only takes 8 seconds. This quite too 
inaccurate.

>
>> +#define CLK_M_OSC	25000000
>
>> +static int dmtimer_init(void)
>> +{
>> +	dmtimer_cs.mult = clocksource_hz2mult(CLK_M_OSC, dmtimer_cs.shift);
>> +	/* Enable counter */
>> +	writel(0x3, base + TCLR);
>> +
>> +	return init_clock(&dmtimer_cs);
>
> You use a fixed M_OSC of 25 MHz, but this value actually depends on the
> the board. The AM335x supports 19.2, 24 and 26 MHz in addition to 25
> MHz.
see new patch.
> The advantage of using dmtimer0 is that it is always available and runs
> at 32KiHz on every board.
>
> Regards,
> Jan
>

Kind regards,
Daniel

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