[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>

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

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

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();
-		local_irq_disable();
+	if (!need_resched())
-		if (likely(!need_resched()))
+		idle_with_irq_disabled();
-			idle_with_irq_disabled();
+
-		local_irq_enable();
+	local_irq_enable();
-	}
 }
 
-void (*idle)(void) = default_idle;
-
 /*
- * The idle thread. There's no useful work to be
+ * The idle thread.  We try to conserve power, while trying to keep
- * done, so just try to conserve power and have a
+ * overall latency low.  The architecture specific idle is passed
- * low exit latency (ie sit in a loop waiting for
+ * a value to indicate the level of "idleness" of the system.
- * somebody to say that they'd like to reschedule)
  */
 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();

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();
+}