linux-kernel - [PATCH v4 7/8] clocksource: kona: Add basic use of external clock

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Date:	Thu, 5 Dec 2013 11:20:43 -0800
From:	Tim Kryger <tim.kryger@...aro.org>
To:	Christian Daudt <bcm@...thebug.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Chris Ball <cjb@...top.org>, Axel Lin <axel.lin@...ics.com>
CC:	Tim Kryger <tim.kryger@...aro.org>,
	Device Tree List <devicetree@...r.kernel.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linaro Patches List <patches@...aro.org>
Subject: [PATCH v4 7/8] 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@...aro.org>
Reviewed-by: Markus Mayer <markus.mayer@...aro.org>
Reviewed-by: Matt Porter <matt.porter@...aro.org>
---
 drivers/clocksource/bcm_kona_timer.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/clocksource/bcm_kona_timer.c b/drivers/clocksource/bcm_kona_timer.c
index 0d7d8c3..8a4ab36 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>
@@ -107,11 +108,18 @@ static const struct of_device_id bcm_timer_ids[] __initconst = {
 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);
-- 
1.8.0.1

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