clocksource: kona: Add basic use of external clock

Tim Kryger · olofj · commit 50ac20610266 · 2014-01-31T21:04:01.000-08:00
When an clock is specified in the device tree, enable it and use it to
determine the external clock frequency.

Signed-off-by: Tim Kryger &lt;tim.kryger@linaro.org&gt;
Reviewed-by: Markus Mayer &lt;markus.mayer@linaro.org&gt;
Reviewed-by: Matt Porter &lt;matt.porter@linaro.org&gt;
Reviewed-by: Christian Daudt &lt;bcm@fixthebug.org&gt;
Acked-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
Signed-off-by: Christian Daudt &lt;bcm@fixthebug.org&gt;
Signed-off-by: Olof Johansson &lt;olof@lixom.net&gt;
diff --git a/drivers/clocksource/bcm_kona_timer.c b/drivers/clocksource/bcm_kona_timer.c
@@ -17,6 +17,7 @@
 #include <linux/jiffies.h>
 #include <linux/clockchips.h>
 #include <linux/types.h>
+#include <linux/clk.h>
 
 #include <linux/io.h>
 #include <asm/mach/time.h>
@@ -101,11 +102,18 @@ kona_timer_get_counter(void *timer_base, uint32_t *msw, uint32_t *lsw)
 static void __init kona_timers_init(struct device_node *node)
 {
 	u32 freq;
+	struct clk *external_clk;
 
-	if (!of_property_read_u32(node, "clock-frequency", &freq))
+	external_clk = of_clk_get_by_name(node, NULL);
+
+	if (!IS_ERR(external_clk)) {
+		arch_timer_rate = clk_get_rate(external_clk);
+		clk_prepare_enable(external_clk);
+	} else if (!of_property_read_u32(node, "clock-frequency", &freq)) {
 		arch_timer_rate = freq;
-	else
-		panic("clock-frequency not set in the .dts file");
+	} else {
+		panic("unable to determine clock-frequency");
+	}
 
 	/* Setup IRQ numbers */
 	timers.tmr_irq = irq_of_parse_and_map(node, 0);
