[ARM] 3638/1: S3C2412: core clocks

Patch from Ben Dooks

Clock support for the clocks on the Samsung S3C2412
and S3C2413 SoCs. This provides clock enables and
parent selection for all the standard clocks.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 711 insertions, 0 deletions

diff --git a/arch/arm/mach-s3c2410/s3c2412-clock.c b/arch/arm/mach-s3c2410/s3c2412-clock.c
new file mode 100644
index 00000000000..c95ed3e1858
--- /dev/null
+++ b/arch/arm/mach-s3c2410/s3c2412-clock.c
@@ -0,0 +1,711 @@
+/* linux/arch/arm/mach-s3c2410/s3c2412-clock.c
+ *
+ * Copyright (c) 2006 Simtec Electronics
+ *	Ben Dooks <ben@simtec.co.uk>
+ *
+ * S3C2412,S3C2413 Clock control support
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+*/
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/errno.h>
+#include <linux/err.h>
+#include <linux/sysdev.h>
+#include <linux/clk.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+
+#include <asm/hardware.h>
+#include <asm/io.h>
+
+#include <asm/arch/regs-clock.h>
+#include <asm/arch/regs-gpio.h>
+
+#include "clock.h"
+#include "cpu.h"
+
+/* We currently have to assume that the system is running
+ * from the XTPll input, and that all ***REFCLKs are being
+ * fed from it, as we cannot read the state of OM[4] from
+ * software.
+ *
+ * It would be possible for each board initialisation to
+ * set the correct muxing at initialisation
+*/
+
+int s3c2412_clkcon_enable(struct clk *clk, int enable)
+{
+	unsigned int clocks = clk->ctrlbit;
+	unsigned long clkcon;
+
+	clkcon = __raw_readl(S3C2410_CLKCON);
+
+	if (enable)
+		clkcon |= clocks;
+	else
+		clkcon &= ~clocks;
+
+	__raw_writel(clkcon, S3C2410_CLKCON);
+
+	return 0;
+}
+
+static int s3c2412_upll_enable(struct clk *clk, int enable)
+{
+	unsigned long upllcon = __raw_readl(S3C2410_UPLLCON);
+	unsigned long orig = upllcon;
+
+	if (!enable)
+		upllcon |= S3C2412_PLLCON_OFF;
+	else
+		upllcon &= ~S3C2412_PLLCON_OFF;
+
+	__raw_writel(upllcon, S3C2410_UPLLCON);
+
+	/* allow ~150uS for the PLL to settle and lock */
+
+	if (enable && (orig & S3C2412_PLLCON_OFF))
+		udelay(150);
+
+	return 0;
+}
+
+/* clock selections */
+
+/* CPU EXTCLK input */
+static struct clk clk_ext = {
+	.name		= "extclk",
+	.id		= -1,
+};
+
+static struct clk clk_erefclk = {
+	.name		= "erefclk",
+	.id		= -1,
+};
+
+static struct clk clk_urefclk = {
+	.name		= "urefclk",
+	.id		= -1,
+};
+
+static int s3c2412_setparent_usysclk(struct clk *clk, struct clk *parent)
+{
+	unsigned long clksrc = __raw_readl(S3C2412_CLKSRC);
+
+	if (parent == &clk_urefclk)
+		clksrc &= ~S3C2412_CLKSRC_USYSCLK_UPLL;
+	else if (parent == &clk_upll)
+		clksrc |= S3C2412_CLKSRC_USYSCLK_UPLL;
+	else
+		return -EINVAL;
+
+	clk->parent = parent;
+
+	__raw_writel(clksrc, S3C2412_CLKSRC);
+	return 0;
+}
+
+static struct clk clk_usysclk = {
+	.name		= "usysclk",
+	.id		= -1,
+	.parent		= &clk_xtal,
+	.set_parent	= s3c2412_setparent_usysclk,
+};
+
+static struct clk clk_mrefclk = {
+	.name		= "mrefclk",
+	.parent		= &clk_xtal,
+	.id		= -1,
+};
+
+static struct clk clk_mdivclk = {
+	.name		= "mdivclk",
+	.parent		= &clk_xtal,
+	.id		= -1,
+};
+
+static int s3c2412_setparent_usbsrc(struct clk *clk, struct clk *parent)
+{
+	unsigned long clksrc = __raw_readl(S3C2412_CLKSRC);
+
+	if (parent == &clk_usysclk)
+		clksrc &= ~S3C2412_CLKSRC_USBCLK_HCLK;
+	else if (parent == &clk_h)
+		clksrc |= S3C2412_CLKSRC_USBCLK_HCLK;
+	else
+		return -EINVAL;
+
+	clk->parent = parent;
+
+	__raw_writel(clksrc, S3C2412_CLKSRC);
+	return 0;
+}
+
+static unsigned long s3c2412_roundrate_usbsrc(struct clk *clk,
+					      unsigned long rate)
+{
+	unsigned long parent_rate = clk_get_rate(clk->parent);
+	int div;
+
+	if (rate > parent_rate)
+		return parent_rate;
+
+	div = parent_rate / rate;
+	if (div > 2)
+		div = 2;
+
+	return parent_rate / div;
+}
+
+static unsigned long s3c2412_getrate_usbsrc(struct clk *clk)
+{
+	unsigned long parent_rate = clk_get_rate(clk->parent);
+	unsigned long div = __raw_readl(S3C2410_CLKDIVN);
+
+	return parent_rate / ((div & S3C2412_CLKDIVN_USB48DIV) ? 2 : 1);
+}
+
+static int s3c2412_setrate_usbsrc(struct clk *clk, unsigned long rate)
+{
+	unsigned long parent_rate = clk_get_rate(clk->parent);
+	unsigned long clkdivn = __raw_readl(S3C2410_CLKDIVN);
+
+	rate = s3c2412_roundrate_usbsrc(clk, rate);
+
+	if ((parent_rate / rate) == 2)
+		clkdivn |= S3C2412_CLKDIVN_USB48DIV;
+	else
+		clkdivn &= ~S3C2412_CLKDIVN_USB48DIV;
+
+	__raw_writel(clkdivn, S3C2410_CLKDIVN);
+	return 0;
+}
+
+static struct clk clk_usbsrc = {
+	.name		= "usbsrc",
+	.id		= -1,
+	.get_rate	= s3c2412_getrate_usbsrc,
+	.set_rate	= s3c2412_setrate_usbsrc,
+	.round_rate	= s3c2412_roundrate_usbsrc,
+	.set_parent	= s3c2412_setparent_usbsrc,
+};
+
+static int s3c2412_setparent_msysclk(struct clk *clk, struct clk *parent)
+{
+	unsigned long clksrc = __raw_readl(S3C2412_CLKSRC);
+
+	if (parent == &clk_mdivclk)
+		clksrc &= ~S3C2412_CLKSRC_MSYSCLK_MPLL;
+	else if (parent == &clk_upll)
+		clksrc |= S3C2412_CLKSRC_MSYSCLK_MPLL;
+	else
+		return -EINVAL;
+
+	clk->parent = parent;
+
+	__raw_writel(clksrc, S3C2412_CLKSRC);
+	return 0;
+}
+
+static struct clk clk_msysclk = {
+	.name		= "msysclk",
+	.id		= -1,
+	.set_parent	= s3c2412_setparent_msysclk,
+};
+
+/* these next clocks have an divider immediately after them,
+ * so we can register them with their divider and leave out the
+ * intermediate clock stage
+*/
+static unsigned long s3c2412_roundrate_clksrc(struct clk *clk,
+					      unsigned long rate)
+{
+	unsigned long parent_rate = clk_get_rate(clk->parent);
+	int div;
+
+	if (rate > parent_rate)
+		return parent_rate;
+
+	/* note, we remove the +/- 1 calculations as they cancel out */
+
+	div = (rate / parent_rate);
+
+	if (div < 1)
+		div = 1;
+	else if (div > 16)
+		div = 16;
+
+	return parent_rate / div;
+}
+
+static int s3c2412_setparent_uart(struct clk *clk, struct clk *parent)
+{
+	unsigned long clksrc = __raw_readl(S3C2412_CLKSRC);
+
+	if (parent == &clk_erefclk)
+		clksrc &= ~S3C2412_CLKSRC_UARTCLK_MPLL;
+	else if (parent == &clk_mpll)
+		clksrc |= S3C2412_CLKSRC_UARTCLK_MPLL;
+	else
+		return -EINVAL;
+
+	clk->parent = parent;
+
+	__raw_writel(clksrc, S3C2412_CLKSRC);
+	return 0;
+}
+
+static unsigned long s3c2412_getrate_uart(struct clk *clk)
+{
+	unsigned long parent_rate = clk_get_rate(clk->parent);
+	unsigned long div = __raw_readl(S3C2410_CLKDIVN);
+
+	div &= S3C2412_CLKDIVN_UARTDIV_MASK;
+	div >>= S3C2412_CLKDIVN_UARTDIV_SHIFT;
+
+	return parent_rate / (div + 1);
+}
+
+static int s3c2412_setrate_uart(struct clk *clk, unsigned long rate)
+{
+	unsigned long parent_rate = clk_get_rate(clk->parent);
+	unsigned long clkdivn = __raw_readl(S3C2410_CLKDIVN);
+
+	rate = s3c2412_roundrate_clksrc(clk, rate);
+
+	clkdivn &= ~S3C2412_CLKDIVN_UARTDIV_MASK;
+	clkdivn |= ((parent_rate / rate) - 1) << S3C2412_CLKDIVN_UARTDIV_SHIFT;
+
+	__raw_writel(clkdivn, S3C2410_CLKDIVN);
+	return 0;
+}
+
+static struct clk clk_uart = {
+	.name		= "uartclk",
+	.id		= -1,
+	.get_rate	= s3c2412_getrate_uart,
+	.set_rate	= s3c2412_setrate_uart,
+	.set_parent	= s3c2412_setparent_uart,
+	.round_rate	= s3c2412_roundrate_clksrc,
+};
+
+static int s3c2412_setparent_i2s(struct clk *clk, struct clk *parent)
+{
+	unsigned long clksrc = __raw_readl(S3C2412_CLKSRC);
+
+	if (parent == &clk_erefclk)
+		clksrc &= ~S3C2412_CLKSRC_I2SCLK_MPLL;
+	else if (parent == &clk_mpll)
+		clksrc |= S3C2412_CLKSRC_I2SCLK_MPLL;
+	else
+		return -EINVAL;
+
+	clk->parent = parent;
+
+	__raw_writel(clksrc, S3C2412_CLKSRC);
+	return 0;
+}
+
+static unsigned long s3c2412_getrate_i2s(struct clk *clk)
+{
+	unsigned long parent_rate = clk_get_rate(clk->parent);
+	unsigned long div = __raw_readl(S3C2410_CLKDIVN);
+
+	div &= S3C2412_CLKDIVN_I2SDIV_MASK;
+	div >>= S3C2412_CLKDIVN_I2SDIV_SHIFT;
+
+	return parent_rate / (div + 1);
+}
+
+static int s3c2412_setrate_i2s(struct clk *clk, unsigned long rate)
+{
+	unsigned long parent_rate = clk_get_rate(clk->parent);
+	unsigned long clkdivn = __raw_readl(S3C2410_CLKDIVN);
+
+	rate = s3c2412_roundrate_clksrc(clk, rate);
+
+	clkdivn &= ~S3C2412_CLKDIVN_I2SDIV_MASK;
+	clkdivn |= ((parent_rate / rate) - 1) << S3C2412_CLKDIVN_I2SDIV_SHIFT;
+
+	__raw_writel(clkdivn, S3C2410_CLKDIVN);
+	return 0;
+}
+
+static struct clk clk_i2s = {
+	.name		= "i2sclk",
+	.id		= -1,
+	.get_rate	= s3c2412_getrate_i2s,
+	.set_rate	= s3c2412_setrate_i2s,
+	.set_parent	= s3c2412_setparent_i2s,
+	.round_rate	= s3c2412_roundrate_clksrc,
+};
+
+static int s3c2412_setparent_cam(struct clk *clk, struct clk *parent)
+{
+	unsigned long clksrc = __raw_readl(S3C2412_CLKSRC);
+
+	if (parent == &clk_usysclk)
+		clksrc &= ~S3C2412_CLKSRC_CAMCLK_HCLK;
+	else if (parent == &clk_h)
+		clksrc |= S3C2412_CLKSRC_CAMCLK_HCLK;
+	else
+		return -EINVAL;
+
+	clk->parent = parent;
+
+	__raw_writel(clksrc, S3C2412_CLKSRC);
+	return 0;
+}
+static unsigned long s3c2412_getrate_cam(struct clk *clk)
+{
+	unsigned long parent_rate = clk_get_rate(clk->parent);
+	unsigned long div = __raw_readl(S3C2410_CLKDIVN);
+
+	div &= S3C2412_CLKDIVN_CAMDIV_MASK;
+	div >>= S3C2412_CLKDIVN_CAMDIV_SHIFT;
+
+	return parent_rate / (div + 1);
+}
+
+static int s3c2412_setrate_cam(struct clk *clk, unsigned long rate)
+{
+	unsigned long parent_rate = clk_get_rate(clk->parent);
+	unsigned long clkdivn = __raw_readl(S3C2410_CLKDIVN);
+
+	rate = s3c2412_roundrate_clksrc(clk, rate);
+
+	clkdivn &= ~S3C2412_CLKDIVN_CAMDIV_MASK;
+	clkdivn |= ((parent_rate / rate) - 1) << S3C2412_CLKDIVN_CAMDIV_SHIFT;
+
+	__raw_writel(clkdivn, S3C2410_CLKDIVN);
+	return 0;
+}
+
+static struct clk clk_cam = {
+	.name		= "camif-upll",	/* same as 2440 name */
+	.id		= -1,
+	.get_rate	= s3c2412_getrate_cam,
+	.set_rate	= s3c2412_setrate_cam,
+	.set_parent	= s3c2412_setparent_cam,
+	.round_rate	= s3c2412_roundrate_clksrc,
+};
+
+/* standard clock definitions */
+
+static struct clk init_clocks_disable[] = {
+	{
+		.name		= "nand",
+		.id		= -1,
+		.parent		= &clk_h,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_NAND,
+	}, {
+		.name		= "sdi",
+		.id		= -1,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_SDI,
+	}, {
+		.name		= "adc",
+		.id		= -1,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_ADC,
+	}, {
+		.name		= "i2c",
+		.id		= -1,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_IIC,
+	}, {
+		.name		= "iis",
+		.id		= -1,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_IIS,
+	}, {
+		.name		= "spi",
+		.id		= -1,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_SPI,
+	}
+};
+
+static struct clk init_clocks[] = {
+	{
+		.name		= "dma",
+		.id		= 0,
+		.parent		= &clk_h,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_DMA0,
+	}, {
+		.name		= "dma",
+		.id		= 1,
+		.parent		= &clk_h,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_DMA1,
+	}, {
+		.name		= "dma",
+		.id		= 2,
+		.parent		= &clk_h,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_DMA2,
+	}, {
+		.name		= "dma",
+		.id		= 3,
+		.parent		= &clk_h,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_DMA3,
+	}, {
+		.name		= "lcd",
+		.id		= -1,
+		.parent		= &clk_h,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_LCDC,
+	}, {
+		.name		= "gpio",
+		.id		= -1,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_GPIO,
+	}, {
+		.name		= "usb-host",
+		.id		= -1,
+		.parent		= &clk_h,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_USBH,
+	}, {
+		.name		= "usb-device",
+		.id		= -1,
+		.parent		= &clk_h,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_USBD,
+	}, {
+		.name		= "timers",
+		.id		= -1,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_PWMT,
+	}, {
+		.name		= "uart",
+		.id		= 0,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_UART0,
+	}, {
+		.name		= "uart",
+		.id		= 1,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_UART1,
+	}, {
+		.name		= "uart",
+		.id		= 2,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_UART2,
+	}, {
+		.name		= "rtc",
+		.id		= -1,
+		.parent		= &clk_p,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_RTC,
+	}, {
+		.name		= "watchdog",
+		.id		= -1,
+		.parent		= &clk_p,
+		.ctrlbit	= 0,
+	}, {
+		.name		= "usb-bus-gadget",
+		.id		= -1,
+		.parent		= &clk_usb_bus,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_USB_DEV48,
+	}, {
+		.name		= "usb-bus-host",
+		.id		= -1,
+		.parent		= &clk_usb_bus,
+		.enable		= s3c2412_clkcon_enable,
+		.ctrlbit	= S3C2412_CLKCON_USB_HOST48,
+	}
+};
+
+/* clocks to add where we need to check their parentage */
+
+struct clk_init {
+	struct clk	*clk;
+	unsigned int	 bit;
+	struct clk	*src_0;
+	struct clk	*src_1;
+};
+
+struct clk_init clks_src[] __initdata = {
+	{
+		.clk	= &clk_usysclk,
+		.bit	= S3C2412_CLKSRC_USBCLK_HCLK,
+		.src_0	= &clk_urefclk,
+		.src_1	= &clk_upll,
+	}, {
+		.clk	= &clk_i2s,
+		.bit	= S3C2412_CLKSRC_I2SCLK_MPLL,
+		.src_0	= &clk_erefclk,
+		.src_1	= &clk_mpll,
+	}, {
+		.clk	= &clk_cam,
+		.bit	= S3C2412_CLKSRC_CAMCLK_HCLK,
+		.src_0	= &clk_usysclk,
+		.src_1	= &clk_h,
+	}, {
+		.clk	= &clk_msysclk,
+		.bit	= S3C2412_CLKSRC_MSYSCLK_MPLL,
+		.src_0	= &clk_mdivclk,
+		.src_1	= &clk_mpll,
+	}, {
+		.clk	= &clk_uart,
+		.bit	= S3C2412_CLKSRC_UARTCLK_MPLL,
+		.src_0	= &clk_erefclk,
+		.src_1	= &clk_mpll,
+	}, {
+		.clk	= &clk_usbsrc,
+		.bit	= S3C2412_CLKSRC_USBCLK_HCLK,
+		.src_0	= &clk_usysclk,
+		.src_1	= &clk_h,
+	},
+};
+
+/* s3c2412_clk_initparents
+ *
+ * Initialise the parents for the clocks that we get at start-time
+*/
+
+static void __init s3c2412_clk_initparents(void)
+{
+	unsigned long clksrc = __raw_readl(S3C2412_CLKSRC);
+	struct clk_init *cip = clks_src;
+	struct clk *src;
+	int ptr;
+	int ret;
+
+	for (ptr = 0; ptr < ARRAY_SIZE(clks_src); ptr++, cip++) {
+		ret = s3c24xx_register_clock(cip->clk);
+		if (ret < 0) {
+			printk(KERN_ERR "Failed to register clock %s (%d)\n",
+			       cip->clk->name, ret);
+		}
+
+		src = (clksrc & cip->bit) ? cip->src_1 : cip->src_0;
+
+		printk(KERN_INFO "%s: parent %s\n", cip->clk->name, src->name);
+		clk_set_parent(cip->clk, src);
+	}
+}
+
+/* clocks to add straight away */
+
+struct clk *clks[] __initdata = {
+	&clk_ext,
+	&clk_usb_bus,
+	&clk_erefclk,
+	&clk_urefclk,
+	&clk_mrefclk,
+};
+
+int __init s3c2412_baseclk_add(void)
+{
+	unsigned long clkcon  = __raw_readl(S3C2410_CLKCON);
+	struct clk *clkp;
+	int ret;
+	int ptr;
+
+	clk_upll.enable = s3c2412_upll_enable;
+	clk_usb_bus.parent = &clk_usbsrc;
+	clk_usb_bus.rate = 0x0;
+
+	s3c2412_clk_initparents();
+
+	for (ptr = 0; ptr < ARRAY_SIZE(clks); ptr++) {
+		clkp = clks[ptr];
+
+		ret = s3c24xx_register_clock(clkp);
+		if (ret < 0) {
+			printk(KERN_ERR "Failed to register clock %s (%d)\n",
+			       clkp->name, ret);
+		}
+	}
+
+	/* ensure usb bus clock is within correct rate of 48MHz */
+
+	if (clk_get_rate(&clk_usb_bus) != (48 * 1000 * 1000)) {
+		printk(KERN_INFO "Warning: USB bus clock not at 48MHz\n");
+
+		/* for the moment, let's use the UPLL, and see if we can
+		 * get 48MHz */
+
+		clk_set_parent(&clk_usysclk, &clk_upll);
+		clk_set_parent(&clk_usbsrc, &clk_usysclk);
+		clk_set_rate(&clk_usbsrc, 48*1000*1000);
+	}
+
+	printk("S3C2412: upll %s, %ld.%03ld MHz, usb-bus %ld.%03ld MHz\n",
+	       (__raw_readl(S3C2410_UPLLCON) & S3C2412_PLLCON_OFF) ? "off":"on",
+	       print_mhz(clk_get_rate(&clk_upll)),
+	       print_mhz(clk_get_rate(&clk_usb_bus)));
+
+	/* register clocks from clock array */
+
+	clkp = init_clocks;
+	for (ptr = 0; ptr < ARRAY_SIZE(init_clocks); ptr++, clkp++) {
+		/* ensure that we note the clock state */
+
+		clkp->usage = clkcon & clkp->ctrlbit ? 1 : 0;
+
+		ret = s3c24xx_register_clock(clkp);
+		if (ret < 0) {
+			printk(KERN_ERR "Failed to register clock %s (%d)\n",
+			       clkp->name, ret);
+		}
+	}
+
+	/* We must be careful disabling the clocks we are not intending to
+	 * be using at boot time, as subsytems such as the LCD which do
+	 * their own DMA requests to the bus can cause the system to lockup
+	 * if they where in the middle of requesting bus access.
+	 *
+	 * Disabling the LCD clock if the LCD is active is very dangerous,
+	 * and therefore the bootloader should be careful to not enable
+	 * the LCD clock if it is not needed.
+	*/
+
+	/* install (and disable) the clocks we do not need immediately */
+
+	clkp = init_clocks_disable;
+	for (ptr = 0; ptr < ARRAY_SIZE(init_clocks_disable); ptr++, clkp++) {
+
+		ret = s3c24xx_register_clock(clkp);
+		if (ret < 0) {
+			printk(KERN_ERR "Failed to register clock %s (%d)\n",
+			       clkp->name, ret);
+		}
+
+		s3c2412_clkcon_enable(clkp, 0);
+	}
+
+	return 0;
+}