ARCv2: SMP: clocksource: Enable Global Real Time counter

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

arch/arc/kernel/mcip.c

@@ -154,4 +154,7 @@ void mcip_init_early_smp(void)
 		__mcip_cmd_data(CMD_DEBUG_SET_SELECT, 0, 0xf);
 		__mcip_cmd_data(CMD_DEBUG_SET_MASK, 0xf, 0xf);
 	}
+
+	if (IS_ENABLED(CONFIG_ARC_HAS_GRTC) && !mp.grtc)
+		panic("kernel trying to use non-existent GRTC\n");
 }

arch/arc/kernel/time.c

@@ -45,6 +45,8 @@
 #include <asm/clk.h>
 #include <asm/mach_desc.h>
 
+#include <asm/mcip.h>
+
 /* Timer related Aux registers */
 #define ARC_REG_TIMER0_LIMIT	0x23	/* timer 0 limit */
 #define ARC_REG_TIMER0_CTRL	0x22	/* timer 0 control */
@@ -60,6 +62,48 @@
 
 /********** Clock Source Device *********/
 
+#ifdef CONFIG_ARC_HAS_GRTC
+
+static int arc_counter_setup(void)
+{
+	return 1;
+}
+
+static cycle_t arc_counter_read(struct clocksource *cs)
+{
+	unsigned long flags;
+	union {
+#ifdef CONFIG_CPU_BIG_ENDIAN
+		struct { u32 h, l; };
+#else
+		struct { u32 l, h; };
+#endif
+		cycle_t  full;
+	} stamp;
+
+	local_irq_save(flags);
+
+	__mcip_cmd(CMD_GRTC_READ_LO, 0);
+	stamp.l = read_aux_reg(ARC_REG_MCIP_READBACK);
+
+	__mcip_cmd(CMD_GRTC_READ_HI, 0);
+	stamp.h = read_aux_reg(ARC_REG_MCIP_READBACK);
+
+	local_irq_restore(flags);
+
+	return stamp.full;
+}
+
+static struct clocksource arc_counter = {
+	.name   = "ARConnect GRTC",
+	.rating = 400,
+	.read   = arc_counter_read,
+	.mask   = CLOCKSOURCE_MASK(64),
+	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+#else
+
 #ifdef CONFIG_ARC_HAS_RTC
 
 #define AUX_RTC_CTRL	0x103
@@ -134,6 +178,7 @@ static struct clocksource arc_counter = {
 	.flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
+#endif
 #endif
 
 /********** Clock Event Device *********/