Re: [PATCH v3 2/2] ARM: am335x: Changed timer

2015-07-19 Thread Sascha Hauer
On Fri, Jul 17, 2015 at 04:57:48PM +0200, Jan Lübbe wrote:
> On Fr, 2015-07-17 at 15:39 +0200, Daniel Schultz wrote:
> > The dmtimer0 is too inaccurate to be used for measurements.
> > We switch to the more accurate dmtimer2.
> 
> Ah, OK, after looking at the TRM again, the real reason for the
> inaccuracy seems to be that the 32KiHz for dmtimer0 is *not* derived
> from the RTC crystal, but from an internal RC oscillator.
> 
> The kernel uses dmtimer1 for the clocksource by switching it to the
> M_OSC in the PRCM.
> 
> The dmtimer2 is used for clockevents and runs from M_OSC by default.
> While we could set the dmtimer1 source to M_OSC in the clock setup, it
> seems simpler to just use dmtimer2.
> 
> The commit message should explain the reasoning behind the switch.

Changed the commit message while applying to:

The 32KHz from dmtimer0 is derived from a SoC internal RC oscillator
which is quite inaccurate. Switch to dmtimer2 which is driven from
the high frequency oscillator clock.

Sascha

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Re: [PATCH v3 2/2] ARM: am335x: Changed timer

2015-07-17 Thread Jan Lübbe
On Fr, 2015-07-17 at 15:39 +0200, Daniel Schultz wrote:
> The dmtimer0 is too inaccurate to be used for measurements.
> We switch to the more accurate dmtimer2.

Ah, OK, after looking at the TRM again, the real reason for the
inaccuracy seems to be that the 32KiHz for dmtimer0 is *not* derived
from the RTC crystal, but from an internal RC oscillator.

The kernel uses dmtimer1 for the clocksource by switching it to the
M_OSC in the PRCM.

The dmtimer2 is used for clockevents and runs from M_OSC by default.
While we could set the dmtimer1 source to M_OSC in the clock setup, it
seems simpler to just use dmtimer2.

The commit message should explain the reasoning behind the switch.

Regards,
Jan
-- 
Pengutronix e.K.   | |
Industrial Linux Solutions | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0|
Amtsgericht Hildesheim, HRA 2686   | Fax:   +49-5121-206917- |


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[PATCH v3 2/2] ARM: am335x: Changed timer

2015-07-17 Thread Daniel Schultz
The dmtimer0 is too inaccurate to be used for measurements.
We switch to the more accurate dmtimer2.

Signed-off-by: Daniel Schultz 
---
 arch/arm/mach-omap/Kconfig   |   4 +-
 arch/arm/mach-omap/Makefile  |   2 +-
 arch/arm/mach-omap/dmtimer.c | 112 +++
 arch/arm/mach-omap/dmtimer0.c|  85 -
 arch/arm/mach-omap/include/mach/am33xx-silicon.h |   4 +
 5 files changed, 119 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 000..56adda0
--- /dev/null
+++ b/arch/arm/mach-omap/dmtimer.c
@@ -0,0 +1,112 @@
+/**
+ * @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, 
+ * Nishanth Menon 
+ *
+ * (C) Copyright 2012 Phytec Messtechnik GmbH
+ * Author: Teresa Gámez 
+ * (C) Copyright 2015 Phytec Messtechnik GmbH
+ * Author: Daniel Schultz 
+ *
+ * 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 
+#include 
+#include 
+#include 
+
+#include 
+
+#define CLK_RC32K  32768
+
+#define TIDR   0x0
+#define TIOCP_CFG  0x10
+#define IRQ_EOI0x20
+#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)
+{
+   u64 clk_speed;
+   int sysboot;
+
+   sysboot = (readl(AM33XX_CTRL_STATUS) >> 22) & 3;
+   switch (sysboot) {
+   case 0:
+   clk_speed = 1920;
+   break;
+   case 1:
+   clk_speed = 2400;
+   break;
+   case 2:
+   clk_speed = 2500;
+   break;
+   case 3:
+   clk_speed = 2600;
+   break;
+   }
+
+   dmtimer_cs.mult = clocksource_hz2mult(clk_speed, 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 mo