[PATCH v3 1/3] ARM: shmobile: sh73a0: wait for completion when kicking the clock

[Guennadi Liakhovetski]

To reconfigure clocks, controlled by FRQCRA and FRQCRB, a kick bit has to
be set and to make sure the setting has taken effect, it has to be read
back repeatedly until it is cleared by the hardware. This patch adds the
waiting part, that was missing until now.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski at gmx.de>
---

As noted in patch 0/3, this patch affects existing systems, but AFAICS 
only theoretically - so far nobody is changing clock rates of any of the 
FRQCRA and FRQCRB clocks. Still, please, handle with care.

 arch/arm/mach-shmobile/clock-sh73a0.c |   23 +++++++++++++++++------
 1 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/arch/arm/mach-shmobile/clock-sh73a0.c b/arch/arm/mach-shmobile/clock-sh73a0.c
index 71843dd..34b5c5a 100644
--- a/arch/arm/mach-shmobile/clock-sh73a0.c
+++ b/arch/arm/mach-shmobile/clock-sh73a0.c
@@ -21,6 +21,7 @@
 #include <linux/io.h>
 #include <linux/sh_clk.h>
 #include <linux/clkdev.h>
+#include <asm/processor.h>
 #include <mach/common.h>
 
 #define FRQCRA		IOMEM(0xe6150000)
@@ -234,14 +235,24 @@ static struct clk *main_clks[] = {
 	&sh73a0_extalr_clk,
 };
 
-static void div4_kick(struct clk *clk)
+static int frqcr_kick(void)
 {
-	unsigned long value;
+	int i;
+
+	/* set KICK bit in FRQCRB to update hardware setting, check success */
+	__raw_writel(__raw_readl(FRQCRB) | (1 << 31), FRQCRB);
+	for (i = 1000; i; i--)
+		if (__raw_readl(FRQCRB) & (1 << 31))
+			cpu_relax();
+		else
+			return i;
+
+	return -ETIMEDOUT;
+}
 
-	/* set KICK bit in FRQCRB to update hardware setting */
-	value = __raw_readl(FRQCRB);
-	value |= (1 << 31);
-	__raw_writel(value, FRQCRB);
+static void div4_kick(struct clk *clk)
+{
+	frqcr_kick();
 }
 
 static int divisors[] = { 2, 3, 4, 6, 8, 12, 16, 18,
-- 
1.7.2.5