[Blackfin] arch: initial generic time and clock sources

This patch enables Hight-Res Timers and tickless kernel

Signed-off-by: Vitja Makarov <vitja.makarov@gmail.com>
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

4 files changed, 253 insertions, 20 deletions

diff --git a/arch/blackfin/Kconfig b/arch/blackfin/Kconfig
index 2dd1f300a5cf..a3cf9d0a528b 100644
--- a/arch/blackfin/Kconfig
+++ b/arch/blackfin/Kconfig
@@ -47,10 +47,6 @@ config GENERIC_IRQ_PROBE
         bool
         default y
 
-config GENERIC_TIME
-        bool
-        default n
-
 config GENERIC_GPIO
         bool
         default y
@@ -415,6 +411,30 @@ comment "Kernel Timer/Scheduler"
 
 source kernel/Kconfig.hz
 
+config GENERIC_TIME
+        bool "Generic time"
+        default y
+
+config GENERIC_CLOCKEVENTS
+        bool "Generic clock events"
+        depends on GENERIC_TIME
+        default y
+
+config CYCLES_CLOCKSOURCE
+        bool "Use 'CYCLES' as a clocksource (EXPERIMENTAL)"
+        depends on EXPERIMENTAL
+        depends on GENERIC_CLOCKEVENTS
+        depends on !BFIN_SCRATCH_REG_CYCLES
+        default n
+        help
+          If you say Y here, you will enable support for using the 'cycles'
+          registers as a clock source.  Doing so means you will be unable to
+          safely write to the 'cycles' register during runtime.  You will
+          still be able to read it (such as for performance monitoring), but
+          writing the registers will most likely crash the kernel.
+
+source kernel/time/Kconfig
+
 comment "Memory Setup"
 
 config MEM_SIZE
diff --git a/arch/blackfin/kernel/Makefile b/arch/blackfin/kernel/Makefile
index 318b9b692a48..6140cd69c782 100644
--- a/arch/blackfin/kernel/Makefile
+++ b/arch/blackfin/kernel/Makefile
@@ -6,9 +6,15 @@ extra-y := init_task.o vmlinux.lds
 
 obj-y := \
         entry.o process.o bfin_ksyms.o ptrace.o setup.o signal.o \
-        sys_bfin.o time.o traps.o irqchip.o dma-mapping.o flat.o \
+        sys_bfin.o traps.o irqchip.o dma-mapping.o flat.o \
         fixed_code.o reboot.o bfin_gpio.o
 
+ifeq ($(CONFIG_GENERIC_CLOCKEVENTS),y)
+    obj-y += time-ts.o
+else
+    obj-y += time.o
+endif
+
 obj-$(CONFIG_BFIN_GPTIMERS)          += gptimers.o
 obj-$(CONFIG_MODULES)                += module.o
 obj-$(CONFIG_BFIN_DMA_5XX)           += bfin_dma_5xx.o
diff --git a/arch/blackfin/kernel/process.c b/arch/blackfin/kernel/process.c
index 6b8459c66163..6dedb2da8b67 100644
--- a/arch/blackfin/kernel/process.c
+++ b/arch/blackfin/kernel/process.c
@@ -32,6 +32,8 @@
 #include <linux/unistd.h>
 #include <linux/user.h>
 #include <linux/uaccess.h>
+#include <linux/sched.h>
+#include <linux/tick.h>
 #include <linux/fs.h>
 #include <linux/err.h>
 
@@ -69,33 +71,44 @@ EXPORT_SYMBOL(pm_power_off);
  * The idle loop on BFIN
  */
 #ifdef CONFIG_IDLE_L1
-void default_idle(void)__attribute__((l1_text));
+static void default_idle(void)__attribute__((l1_text));
 void cpu_idle(void)__attribute__((l1_text));
 #endif
 
-void default_idle(void)
+/*
+ * This is our default idle handler.  We need to disable
+ * interrupts here to ensure we don't miss a wakeup call.
+ */
+static void default_idle(void)
 {
-        while (!need_resched()) {
-                local_irq_disable();
-                if (likely(!need_resched()))
-                        idle_with_irq_disabled();
-                local_irq_enable();
-        }
-}
+        local_irq_disable();
+        if (!need_resched())
+                idle_with_irq_disabled();
 
-void (*idle)(void) = default_idle;
+        local_irq_enable();
+}
 
 /*
- * The idle thread. There's no useful work to be
- * done, so just try to conserve power and have a
- * low exit latency (ie sit in a loop waiting for
- * somebody to say that they'd like to reschedule)
+ * The idle thread.  We try to conserve power, while trying to keep
+ * overall latency low.  The architecture specific idle is passed
+ * a value to indicate the level of "idleness" of the system.
  */
 void cpu_idle(void)
 {
         /* endless idle loop with no priority at all */
         while (1) {
-                idle();
+                void (*idle)(void) = pm_idle;
+
+#ifdef CONFIG_HOTPLUG_CPU
+                if (cpu_is_offline(smp_processor_id()))
+                        cpu_die();
+#endif
+                if (!idle)
+                        idle = default_idle;
+                tick_nohz_stop_sched_tick();
+                while (!need_resched())
+                        idle();
+                tick_nohz_restart_sched_tick();
                 preempt_enable_no_resched();
                 schedule();
                 preempt_disable();
diff --git a/arch/blackfin/kernel/time-ts.c b/arch/blackfin/kernel/time-ts.c
new file mode 100644
index 000000000000..3aad6d710726
--- /dev/null
+++ b/arch/blackfin/kernel/time-ts.c
@@ -0,0 +1,194 @@
+/*
+ * linux/arch/kernel/time-ts.c
+ *
+ * Based on arm clockevents implementation and old bfin time tick.
+ *
+ * Copyright(C) 2008, GeoTechnologies, Vitja Makarov
+ *
+ * This code is licenced under the GPL version 2. For details see
+ * kernel-base/COPYING.
+ */
+#include <linux/module.h>
+#include <linux/profile.h>
+#include <linux/interrupt.h>
+#include <linux/time.h>
+#include <linux/irq.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+
+#include <asm/blackfin.h>
+
+#ifdef CONFIG_CYCLES_CLOCKSOURCE
+
+static unsigned long cyc2ns_scale;
+#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
+
+static inline void set_cyc2ns_scale(unsigned long cpu_khz)
+{
+        cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR) / cpu_khz;
+}
+
+static inline unsigned long long cycles_2_ns(cycle_t cyc)
+{
+        return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
+}
+
+static cycle_t read_cycles(void)
+{
+        unsigned long tmp, tmp2;
+        asm("%0 = cycles; %1 = cycles2;" : "=d"(tmp), "=d"(tmp2));
+        return tmp | ((cycle_t)tmp2 << 32);
+}
+
+unsigned long long sched_clock(void)
+{
+        return cycles_2_ns(read_cycles());
+}
+
+static struct clocksource clocksource_bfin = {
+        .name           = "bfin_cycles",
+        .rating         = 350,
+        .read           = read_cycles,
+        .mask           = CLOCKSOURCE_MASK(64),
+        .shift          = 22,
+        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static int __init bfin_clocksource_init(void)
+{
+        set_cyc2ns_scale(get_cclk() / 1000);
+
+        clocksource_bfin.mult = clocksource_hz2mult(get_cclk(), clocksource_bfin.shift);
+
+        if (clocksource_register(&clocksource_bfin))
+                panic("failed to register clocksource");
+
+        return 0;
+}
+
+#else
+# define bfin_clocksource_init()
+#endif
+
+static int bfin_timer_set_next_event(unsigned long cycles,
+                                     struct clock_event_device *evt)
+{
+        bfin_write_TCOUNT(cycles);
+        CSYNC();
+        return 0;
+}
+
+static void bfin_timer_set_mode(enum clock_event_mode mode,
+                                struct clock_event_device *evt)
+{
+        switch (mode) {
+        case CLOCK_EVT_MODE_PERIODIC: {
+                unsigned long tcount = ((get_cclk() / (HZ * 1)) - 1);
+                bfin_write_TCNTL(TMPWR);
+                CSYNC();
+                bfin_write_TPERIOD(tcount);
+                bfin_write_TCOUNT(tcount);
+                bfin_write_TCNTL(TMPWR | TMREN | TAUTORLD);
+                CSYNC();
+                break;
+        }
+        case CLOCK_EVT_MODE_ONESHOT:
+                bfin_write_TCOUNT(0);
+                bfin_write_TCNTL(TMPWR | TMREN);
+                CSYNC();
+                break;
+        case CLOCK_EVT_MODE_UNUSED:
+        case CLOCK_EVT_MODE_SHUTDOWN:
+                bfin_write_TCNTL(0);
+                CSYNC();
+                break;
+        case CLOCK_EVT_MODE_RESUME:
+                break;
+        }
+}
+
+static void __init bfin_timer_init(void)
+{
+        /* power up the timer, but don't enable it just yet */
+        bfin_write_TCNTL(TMPWR);
+        CSYNC();
+
+        /*
+         * the TSCALE prescaler counter.
+         */
+        bfin_write_TSCALE(0);
+        bfin_write_TPERIOD(0);
+        bfin_write_TCOUNT(0);
+
+        /* now enable the timer */
+        CSYNC();
+}
+
+/*
+ * timer_interrupt() needs to keep up the real-time clock,
+ * as well as call the "do_timer()" routine every clocktick
+ */
+#ifdef CONFIG_CORE_TIMER_IRQ_L1
+__attribute__((l1_text))
+#endif
+irqreturn_t timer_interrupt(int irq, void *dev_id);
+
+static struct clock_event_device clockevent_bfin = {
+        .name           = "bfin_core_timer",
+        .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+        .shift          = 32,
+        .cpumask        = CPU_MASK_CPU0,
+        .set_next_event = bfin_timer_set_next_event,
+        .set_mode       = bfin_timer_set_mode,
+};
+
+static struct irqaction bfin_timer_irq = {
+        .name           = "Blackfin Core Timer",
+        .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
+        .handler        = timer_interrupt,
+        .dev_id         = &clockevent_bfin,
+};
+
+irqreturn_t timer_interrupt(int irq, void *dev_id)
+{
+        struct clock_event_device *evt = dev_id;
+        evt->event_handler(evt);
+        return IRQ_HANDLED;
+}
+
+static int __init bfin_clockevent_init(void)
+{
+        setup_irq(IRQ_CORETMR, &bfin_timer_irq);
+        bfin_timer_init();
+
+        clockevent_bfin.mult = div_sc(get_cclk(), NSEC_PER_SEC, clockevent_bfin.shift);
+        clockevent_bfin.max_delta_ns = clockevent_delta2ns(-1, &clockevent_bfin);
+        clockevent_bfin.min_delta_ns = clockevent_delta2ns(100, &clockevent_bfin);
+        clockevents_register_device(&clockevent_bfin);
+
+        return 0;
+}
+
+void __init time_init(void)
+{
+        time_t secs_since_1970 = (365 * 37 + 9) * 24 * 60 * 60; /* 1 Jan 2007 */
+
+#ifdef CONFIG_RTC_DRV_BFIN
+        /* [#2663] hack to filter junk RTC values that would cause
+         * userspace to have to deal with time values greater than
+         * 2^31 seconds (which uClibc cannot cope with yet)
+         */
+        if ((bfin_read_RTC_STAT() & 0xC0000000) == 0xC0000000) {
+                printk(KERN_NOTICE "bfin-rtc: invalid date; resetting\n");
+                bfin_write_RTC_STAT(0);
+        }
+#endif
+
+        /* Initialize xtime. From now on, xtime is updated with timer interrupts */
+        xtime.tv_sec = secs_since_1970;
+        xtime.tv_nsec = 0;
+        set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
+
+        bfin_clocksource_init();
+        bfin_clockevent_init();
+}