clocksource/drivers/tango_xtal: Add new timer for Tango SoCs

Sigma Designs Tango platforms provide a 27 MHz crystal oscillator.
Use it for clocksource, sched_clock, and delay_timer.
Signed-off-by: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/Kconfig

@@ -279,6 +279,10 @@ config CLKSRC_MIPS_GIC
 	depends on MIPS_GIC
 	select CLKSRC_OF
 
+config CLKSRC_TANGO_XTAL
+	bool
+	select CLKSRC_OF
+
 config CLKSRC_PXA
 	def_bool y if ARCH_PXA || ARCH_SA1100
 	select CLKSRC_OF if OF

drivers/clocksource/Makefile

@@ -56,6 +56,7 @@ obj-$(CONFIG_ARCH_KEYSTONE)		+= timer-keystone.o
 obj-$(CONFIG_ARCH_INTEGRATOR_AP)	+= timer-integrator-ap.o
 obj-$(CONFIG_CLKSRC_VERSATILE)		+= versatile.o
 obj-$(CONFIG_CLKSRC_MIPS_GIC)		+= mips-gic-timer.o
+obj-$(CONFIG_CLKSRC_TANGO_XTAL)		+= tango_xtal.o
 obj-$(CONFIG_CLKSRC_IMX_GPT)		+= timer-imx-gpt.o
 obj-$(CONFIG_ASM9260_TIMER)		+= asm9260_timer.o
 obj-$(CONFIG_H8300)			+= h8300_timer8.o

drivers/clocksource/tango_xtal.c

+#include <linux/clocksource.h>
+#include <linux/sched_clock.h>
+#include <linux/of_address.h>
+#include <linux/printk.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/clk.h>
+
+static void __iomem *xtal_in_cnt;
+static struct delay_timer delay_timer;
+
+static unsigned long notrace read_xtal_counter(void)
+{
+	return readl_relaxed(xtal_in_cnt);
+}
+
+static u64 notrace read_sched_clock(void)
+{
+	return read_xtal_counter();
+}
+
+static cycle_t read_clocksource(struct clocksource *cs)
+{
+	return read_xtal_counter();
+}
+
+static struct clocksource tango_xtal = {
+	.name	= "tango-xtal",
+	.rating	= 350,
+	.read	= read_clocksource,
+	.mask	= CLOCKSOURCE_MASK(32),
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static void __init tango_clocksource_init(struct device_node *np)
+{
+	struct clk *clk;
+	int xtal_freq, ret;
+
+	xtal_in_cnt = of_iomap(np, 0);
+	if (xtal_in_cnt == NULL) {
+		pr_err("%s: invalid address\n", np->full_name);
+		return;
+	}
+
+	clk = of_clk_get(np, 0);
+	if (IS_ERR(clk)) {
+		pr_err("%s: invalid clock\n", np->full_name);
+		return;
+	}
+
+	xtal_freq = clk_get_rate(clk);
+	delay_timer.freq = xtal_freq;
+	delay_timer.read_current_timer = read_xtal_counter;
+
+	ret = clocksource_register_hz(&tango_xtal, xtal_freq);
+	if (ret != 0) {
+		pr_err("%s: registration failed\n", np->full_name);
+		return;
+	}
+
+	sched_clock_register(read_sched_clock, 32, xtal_freq);
+	register_current_timer_delay(&delay_timer);
+}
+
+CLOCKSOURCE_OF_DECLARE(tango, "sigma,tick-counter", tango_clocksource_init);