ARM: S3C2440: move handling of fclk/n clock to platform code

s3c2440 uses fclk/n (fclk divided by n) clock as one of the possible clocks used
to generate the baud rate clock. The divider 'n' in this case can be logically
represented outside of the uart controller.

This patch creates a new clock by name "fclk_n" for s3c2440 based platforms to
represent the fclk/n clock in the platform code. This clock provides a get_rate
callback that checks the UCON0/1/2 registers to determine the clock rate. The
samsung uart driver would receive the "fclk_n" clock name as one of the possible
baud rate clock options and the driver need not determine clock rate of fclk/n.

Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Vasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/arch/arm/mach-s3c2440/clock.c b/arch/arm/mach-s3c2440/clock.c
index f9e6bdaf41d..f85853c5d5e 100644
--- a/arch/arm/mach-s3c2440/clock.c
+++ b/arch/arm/mach-s3c2440/clock.c
@@ -34,6 +34,7 @@
 #include <linux/mutex.h>
 #include <linux/clk.h>
 #include <linux/io.h>
+#include <linux/serial_core.h>
 
 #include <mach/hardware.h>
 #include <linux/atomic.h>
@@ -43,6 +44,7 @@
 
 #include <plat/clock.h>
 #include <plat/cpu.h>
+#include <plat/regs-serial.h>
 
 /* S3C2440 extended clock support */
 
@@ -108,6 +110,40 @@ static struct clk s3c2440_clk_ac97 = {
 	.ctrlbit	= S3C2440_CLKCON_CAMERA,
 };
 
+static unsigned long  s3c2440_fclk_n_getrate(struct clk *clk)
+{
+	unsigned long ucon0, ucon1, ucon2, divisor;
+
+	/* the fun of calculating the uart divisors on the s3c2440 */
+	ucon0 = __raw_readl(S3C24XX_VA_UART0 + S3C2410_UCON);
+	ucon1 = __raw_readl(S3C24XX_VA_UART1 + S3C2410_UCON);
+	ucon2 = __raw_readl(S3C24XX_VA_UART2 + S3C2410_UCON);
+
+	ucon0 &= S3C2440_UCON0_DIVMASK;
+	ucon1 &= S3C2440_UCON1_DIVMASK;
+	ucon2 &= S3C2440_UCON2_DIVMASK;
+
+	if (ucon0 != 0)
+		divisor = (ucon0 >> S3C2440_UCON_DIVSHIFT) + 6;
+	else if (ucon1 != 0)
+		divisor = (ucon1 >> S3C2440_UCON_DIVSHIFT) + 21;
+	else if (ucon2 != 0)
+		divisor = (ucon2 >> S3C2440_UCON_DIVSHIFT) + 36;
+	else
+		/* manual calims 44, seems to be 9 */
+		divisor = 9;
+
+	return clk_get_rate(clk->parent) / divisor;
+}
+
+static struct clk s3c2440_clk_fclk_n = {
+	.name		= "fclk_n",
+	.parent		= &clk_f,
+	.ops		= &(struct clk_ops) {
+		.get_rate	= s3c2440_fclk_n_getrate,
+	},
+};
+
 static int s3c2440_clk_add(struct sys_device *sysdev)
 {
 	struct clk *clock_upll;
@@ -126,6 +162,7 @@ static int s3c2440_clk_add(struct sys_device *sysdev)
 	s3c2440_clk_cam.parent = clock_h;
 	s3c2440_clk_ac97.parent = clock_p;
 	s3c2440_clk_cam_upll.parent = clock_upll;
+	s3c24xx_register_clock(&s3c2440_clk_fclk_n);
 
 	s3c24xx_register_clock(&s3c2440_clk_ac97);
 	s3c24xx_register_clock(&s3c2440_clk_cam);