clocksource: add DBX500 PRCMU Timer support

This patch adds the DBX500 PRCMU Timer driver as a clocksource
and as sched_clock.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Mattias Wallin <mattias.wallin@stericsson.com>
Signed-off-by: Jonas Aaberg <jonas.aberg@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

3 files changed, 120 insertions, 0 deletions

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 34e9c4f88926..999d6a03e436 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -15,3 +15,18 @@ config CLKSRC_MMIO
 
 config DW_APB_TIMER
         bool
+
+config CLKSRC_DBX500_PRCMU
+        bool "Clocksource PRCMU Timer"
+        depends on UX500_SOC_DB5500 || UX500_SOC_DB8500
+        default y
+        help
+          Use the always on PRCMU Timer as clocksource
+
+config CLKSRC_DBX500_PRCMU_SCHED_CLOCK
+        bool "Clocksource PRCMU Timer sched_clock"
+        depends on (CLKSRC_DBX500_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 85ad1646a7b7..8d81a1d32653 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -9,3 +9,4 @@ obj-$(CONFIG_SH_TIMER_TMU)	+= sh_tmu.o
 obj-$(CONFIG_CLKBLD_I8253)      += i8253.o
 obj-$(CONFIG_CLKSRC_MMIO)       += mmio.o
 obj-$(CONFIG_DW_APB_TIMER)      += dw_apb_timer.o
+obj-$(CONFIG_CLKSRC_DBX500_PRCMU)       += clksrc-dbx500-prcmu.o
\ No newline at end of file
diff --git a/drivers/clocksource/clksrc-dbx500-prcmu.c b/drivers/clocksource/clksrc-dbx500-prcmu.c
new file mode 100644
index 000000000000..0ac5093a053a
--- /dev/null
+++ b/drivers/clocksource/clksrc-dbx500-prcmu.c
@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2011
+ *
+ * License Terms: GNU General Public License v2
+ * Author: Mattias Wallin <mattias.wallin@stericsson.com> for ST-Ericsson
+ * Author: Sundar Iyer for ST-Ericsson
+ * sched_clock implementation is based on:
+ * plat-nomadik/timer.c Linus Walleij <linus.walleij@stericsson.com>
+ *
+ * DBx500-PRCMU Timer
+ * The PRCMU has 5 timers which are available in a always-on
+ * power domain.  We use the Timer 4 for our always-on clock
+ * source on DB8500 and Timer 3 on DB5500.
+ */
+#include <linux/clockchips.h>
+#include <linux/clksrc-dbx500-prcmu.h>
+
+#include <asm/sched_clock.h>
+
+#include <mach/setup.h>
+#include <mach/hardware.h>
+
+#define RATE_32K                32768
+
+#define TIMER_MODE_CONTINOUS    0x1
+#define TIMER_DOWNCOUNT_VAL     0xffffffff
+
+#define PRCMU_TIMER_REF         0
+#define PRCMU_TIMER_DOWNCOUNT   0x4
+#define PRCMU_TIMER_MODE        0x8
+
+#define SCHED_CLOCK_MIN_WRAP 131072 /* 2^32 / 32768 */
+
+void __iomem *clksrc_dbx500_timer_base;
+
+static cycle_t clksrc_dbx500_prcmu_read(struct clocksource *cs)
+{
+        u32 count, count2;
+
+        do {
+                count = readl(clksrc_dbx500_timer_base +
+                              PRCMU_TIMER_DOWNCOUNT);
+                count2 = readl(clksrc_dbx500_timer_base +
+                               PRCMU_TIMER_DOWNCOUNT);
+        } while (count2 != count);
+
+        /* Negate because the timer is a decrementing counter */
+        return ~count;
+}
+
+static struct clocksource clocksource_dbx500_prcmu = {
+        .name           = "dbx500-prcmu-timer",
+        .rating         = 300,
+        .read           = clksrc_dbx500_prcmu_read,
+        .shift          = 10,
+        .mask           = CLOCKSOURCE_MASK(32),
+        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+#ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK
+static DEFINE_CLOCK_DATA(cd);
+
+unsigned long long notrace sched_clock(void)
+{
+        u32 cyc;
+
+        if (unlikely(!clksrc_dbx500_timer_base))
+                return 0;
+
+        cyc = clksrc_dbx500_prcmu_read(&clocksource_dbx500_prcmu);
+
+        return cyc_to_sched_clock(&cd, cyc, (u32)~0);
+}
+
+static void notrace clksrc_dbx500_prcmu_update_sched_clock(void)
+{
+        u32 cyc = clksrc_dbx500_prcmu_read(&clocksource_dbx500_prcmu);
+        update_sched_clock(&cd, cyc, (u32)~0);
+}
+#endif
+
+void __init clksrc_dbx500_prcmu_init(void)
+{
+        /*
+         * 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(clksrc_dbx500_timer_base + PRCMU_TIMER_MODE) !=
+            TIMER_MODE_CONTINOUS) {
+                writel(TIMER_MODE_CONTINOUS,
+                       clksrc_dbx500_timer_base + PRCMU_TIMER_MODE);
+                writel(TIMER_DOWNCOUNT_VAL,
+                       clksrc_dbx500_timer_base + PRCMU_TIMER_REF);
+        }
+#ifdef CONFIG_CLKSRC_DBX500_PRCMU_SCHED_CLOCK
+        init_sched_clock(&cd, clksrc_dbx500_prcmu_update_sched_clock,
+                         32, RATE_32K);
+#endif
+        clocksource_calc_mult_shift(&clocksource_dbx500_prcmu,
+                                    RATE_32K, SCHED_CLOCK_MIN_WRAP);
+        clocksource_register(&clocksource_dbx500_prcmu);
+}