clocksource: kona: Add basic use of external clock

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 <tim.kryger@linaro.org>
Reviewed-by: Markus Mayer <markus.mayer@linaro.org>
Reviewed-by: Matt Porter <matt.porter@linaro.org>
Reviewed-by: Christian Daudt <bcm@fixthebug.org>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Christian Daudt <bcm@fixthebug.org>
Signed-off-by: Olof Johansson <olof@lixom.net>

1 files changed, 11 insertions, 3 deletions

diff --git a/drivers/clocksource/bcm_kona_timer.c b/drivers/clocksource/bcm_kona_timer.c
index 5176e761166b..974b2db2fe10 100644
--- 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);