The DB8500 PRCMU Timer is a low resolution timer (32KHz) but have
the advantage of beeing always on. I.e continue to count in all
cpuidle sleep states.
To be able to alternate between another sched_clk driver an config
option is added to be able to remove the sched_clk part.
Signed-off-by: Mattias Wallin <[email protected]>
Acked-by: Linus Walleij <[email protected]>
---
drivers/clocksource/Kconfig | 15 +++++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/clksrc-db8500-prcmu.c | 90 +++++++++++++++++++++++++++++
include/linux/clksrc-db8500-prcmu.h | 17 ++++++
4 files changed, 123 insertions(+), 0 deletions(-)
create mode 100644 drivers/clocksource/clksrc-db8500-prcmu.c
create mode 100644 include/linux/clksrc-db8500-prcmu.h
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 96c9219..d7ee415 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -3,3 +3,18 @@ config CLKSRC_I8253
config CLKSRC_MMIO
bool
+
+config CLKSRC_DB8500_PRCMU
+ bool "Clocksource PRCMU Timer"
+ depends on MFD_DB8500_PRCMU
+ default y
+ help
+ Use the always on PRCMU Timer as clocksource
+
+config CLKSRC_DB8500_PRCMU_SCHED_CLOCK
+ bool "Clocksource PRCMU Timer sched_clock"
+ depends on (CLKSRC_DB8500_PRCMU && !NOMADIK_MTU_SCHED_CLOCK)
+ select HAVE_SCHED_CLOCK
+ default y
+ help
+ Use the always on PRCMU Timer as sched_clock
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index b995942..f2308ba 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -8,3 +8,4 @@ obj-$(CONFIG_SH_TIMER_MTU2) += sh_mtu2.o
obj-$(CONFIG_SH_TIMER_TMU) += sh_tmu.o
obj-$(CONFIG_CLKSRC_I8253) += i8253.o
obj-$(CONFIG_CLKSRC_MMIO) += mmio.o
+obj-$(CONFIG_CLKSRC_DB8500_PRCMU) += clksrc-db8500-prcmu.o
diff --git a/drivers/clocksource/clksrc-db8500-prcmu.c b/drivers/clocksource/clksrc-db8500-prcmu.c
new file mode 100644
index 0000000..f18973d
--- /dev/null
+++ b/drivers/clocksource/clksrc-db8500-prcmu.c
@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ *
+ * License Terms: GNU General Public License v2
+ * Author: Mattias Wallin <[email protected]> for ST-Ericsson
+ * sched_clock implementation is based on:
+ * plat-nomadik/timer.c Linus Walleij <[email protected]>
+ *
+ * Clocksource DB8500 PRCMU Timer
+ * The PRCMU in the DB8500 chip has 5 timers which
+ * are available in an always-on power domain.
+ * Timer 4 is dedicated to our always-on clock source.
+ */
+#include <linux/clockchips.h>
+#include <linux/clksrc-db8500-prcmu.h>
+#include <asm/sched_clock.h>
+#include <mach/setup.h>
+#include <mach/db8500-regs.h>
+#include <mach/hardware.h>
+
+#define RATE_32K (32768)
+
+#define TIMER_MODE_CONTINOUS (0x1)
+#define TIMER_DOWNCOUNT_VAL (0xffffffff)
+
+/* PRCMU Timer 4 */
+#define PRCMU_TIMER_4_REF (prcmu_base + 0x450)
+#define PRCMU_TIMER_4_DOWNCOUNT (prcmu_base + 0x454)
+#define PRCMU_TIMER_4_MODE (prcmu_base + 0x458)
+
+static __iomem void *prcmu_base;
+
+#define SCHED_CLOCK_MIN_WRAP (131072) /* 2^32 / 32768 */
+
+/*
+ * We read the timer twice to make sure the value is stable.
+ * Timer glitches will otherwise occur when reading during a transition.
+ */
+static cycle_t clksrc_db8500_prcmu_read(struct clocksource *cs)
+{
+ u32 count, count2;
+
+ do {
+ count = readl(PRCMU_TIMER_4_DOWNCOUNT);
+ count2 = readl(PRCMU_TIMER_4_DOWNCOUNT);
+ } while (count2 != count);
+
+ /* Negate because the timer is a decrementing counter */
+ return ~count;
+}
+
+static struct clocksource clocksource_db8500_prcmu = {
+ .name = "clksrc-db8500-prcmu-timer4",
+ .rating = 300,
+ .read = clksrc_db8500_prcmu_read,
+ .shift = 10,
+ .mask = CLOCKSOURCE_MASK(32),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+#ifdef CONFIG_CLKSRC_DB8500_PRCMU_SCHED_CLOCK
+static DEFINE_CLOCK_DATA(cd);
+
+static void notrace clksrc_db8500_prcmu_update_sched_clock(void)
+{
+ u32 cyc = clksrc_db8500_prcmu_read(&clocksource_db8500_prcmu);
+ update_sched_clock(&cd, cyc, (u32)~0);
+}
+#endif
+
+void __init clksrc_db8500_prcmu_init(void)
+{
+ prcmu_base = __io_address(U8500_PRCMU_BASE);
+
+ /*
+ * The A9 sub system expects the timer to be configured as
+ * a continous looping timer.
+ * The PRCMU should configure it but if it for some reason
+ * don't we do it here.
+ */
+ if (readl(PRCMU_TIMER_4_MODE) != TIMER_MODE_CONTINOUS) {
+ writel(TIMER_MODE_CONTINOUS, PRCMU_TIMER_4_MODE);
+ writel(TIMER_DOWNCOUNT_VAL, PRCMU_TIMER_4_REF);
+ }
+#ifdef CONFIG_CLKSRC_DB8500_PRCMU_SCHED_CLOCK
+ init_sched_clock(&cd, clksrc_db8500_prcmu_update_sched_clock,
+ 32, RATE_32K);
+#endif
+ clocksource_register_hz(&clocksource_db8500_prcmu, RATE_32K);
+}
diff --git a/include/linux/clksrc-db8500-prcmu.h b/include/linux/clksrc-db8500-prcmu.h
new file mode 100644
index 0000000..42b8587
--- /dev/null
+++ b/include/linux/clksrc-db8500-prcmu.h
@@ -0,0 +1,17 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ *
+ * License Terms: GNU General Public License v2
+ * Author: Mattias Wallin <[email protected]>
+ *
+ */
+#ifndef __CLKSRC_DB8500_PRCMU_H
+#define __CLKSRC_DB8500_PRCMU_H
+
+#ifdef CONFIG_CLKSRC_DB8500_PRCMU
+void __init clksrc_db8500_prcmu_init(void);
+#else
+void __init clksrc_db8500_prcmu_init(void) {}
+#endif
+
+#endif
--
1.7.4.3