ARCv2: clocksource: Introduce 64bit local RTC counter

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/Kconfig

@@ -372,6 +372,11 @@ config ARC_HAS_LL64
 	  dest operands with 2 possible source operands.
 	default y
 
+config ARC_HAS_RTC
+	bool "Local 64-bit r/o cycle counter"
+	default n
+	depends on !SMP
+
 config ARC_NUMBER_OF_INTERRUPTS
 	int "Number of interrupts"
 	range 8 240

arch/arc/kernel/setup.c

@@ -200,9 +200,11 @@ static char *arc_cpu_mumbojumbo(int cpu_id, char *buf, int len)
 		       (unsigned int)(arc_get_core_freq() / 1000000),
 		       (unsigned int)(arc_get_core_freq() / 10000) % 100);
 
-	n += scnprintf(buf + n, len - n, "Timers\t\t: %s%s\nISA Extn\t: ",
+	n += scnprintf(buf + n, len - n, "Timers\t\t: %s%s%s%s\nISA Extn\t: ",
 		       IS_AVAIL1(cpu->timers.t0, "Timer0 "),
-		       IS_AVAIL1(cpu->timers.t1, "Timer1 "));
+		       IS_AVAIL1(cpu->timers.t1, "Timer1 "),
+		       IS_AVAIL2(cpu->timers.rtc, "64-bit RTC ",
+				 CONFIG_ARC_HAS_RTC));
 
 	n += i = scnprintf(buf + n, len - n, "%s%s%s%s%s",
 			   IS_AVAIL2(atomic, "atomic ", CONFIG_ARC_HAS_LLSC),
@@ -290,6 +292,9 @@ static void arc_chk_core_config(void)
 	if (!cpu->timers.t1)
 		panic("Timer1 is not present!\n");
 
+	if (IS_ENABLED(CONFIG_ARC_HAS_RTC) && !cpu->timers.rtc)
+		panic("RTC is not present\n");
+
 #ifdef CONFIG_ARC_HAS_DCCM
 	/*
 	 * DCCM can be arbit placed in hardware.

arch/arc/kernel/time.c

@@ -60,6 +60,54 @@
 
 /********** Clock Source Device *********/
 
+#ifdef CONFIG_ARC_HAS_RTC
+
+#define AUX_RTC_CTRL	0x103
+#define AUX_RTC_LOW	0x104
+#define AUX_RTC_HIGH	0x105
+
+int arc_counter_setup(void)
+{
+	write_aux_reg(AUX_RTC_CTRL, 1);
+
+	/* Not usable in SMP */
+	return !IS_ENABLED(CONFIG_SMP);
+}
+
+static cycle_t arc_counter_read(struct clocksource *cs)
+{
+	unsigned long status;
+	union {
+#ifdef CONFIG_CPU_BIG_ENDIAN
+		struct { u32 high, low; };
+#else
+		struct { u32 low, high; };
+#endif
+		cycle_t  full;
+	} stamp;
+
+
+	__asm__ __volatile(
+	"1:						\n"
+	"	lr		%0, [AUX_RTC_LOW]	\n"
+	"	lr		%1, [AUX_RTC_HIGH]	\n"
+	"	lr		%2, [AUX_RTC_CTRL]	\n"
+	"	bbit0.nt	%2, 31, 1b		\n"
+	: "=r" (stamp.low), "=r" (stamp.high), "=r" (status));
+
+	return stamp.full;
+}
+
+static struct clocksource arc_counter = {
+	.name   = "ARCv2 RTC",
+	.rating = 350,
+	.read   = arc_counter_read,
+	.mask   = CLOCKSOURCE_MASK(64),
+	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+#else /* !CONFIG_ARC_HAS_RTC */
+
 /*
  * set 32bit TIMER1 to keep counting monotonically and wraparound
  */
@@ -86,6 +134,8 @@ static struct clocksource arc_counter = {
 	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
+#endif
+
 /********** Clock Event Device *********/
 
 /*