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>

diff --git a/drivers/clocksource/bcm_kona_timer.c b/drivers/clocksource/bcm_kona_timer.c
index 5176e761166b27a0730341ec1688ae5157cf6258..974b2db2fe1087b05499a8dc2aaaa53338c985e4 100644 (file)
--- 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);