MXC family: Add clock handling

Internal clock path handling for the mxc CPUs.

Changed against the original Freescale code (and against clocklib for example):
- clock rate is always calculated whenever one ask for the current rate
(means struct clk has no more a member called "rate"). So switching the PLL
base frequency will propagate immediately to all other clocks that are
depending on this frequency.

Signed-off-by: Juergen Beisert <[e-mail]>

arch/arm/plat-mxc/Makefile

···
 #
 
 # Common support
-obj-y := irq.o
+obj-y := irq.o clock.o

arch/arm/plat-mxc/clock.c

···
+/*
+ * Based on arch/arm/plat-omap/clock.c
+ *
+ * Copyright (C) 2004 - 2005 Nokia corporation
+ * Written by Tuukka Tikkanen <[e-mail]>
+ * Modified for omap shared clock framework by Tony Lindgren <[e-mail]>
+ * Copyright 2007 Freescale Semiconductor, Inc. All Rights Reserved.
+ * Copyright 2008 Juergen Beisert, [e-mail]
+ *
+ * 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., 51 Franklin Street, Fifth Floor, Boston,
+ * MA  02110-1301, USA.
+ */
+
+/* #define DEBUG */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/platform_device.h>
+#include <linux/proc_fs.h>
+#include <linux/semaphore.h>
+#include <linux/string.h>
+#include <linux/version.h>
+
+#include <asm/arch/clock.h>
+
+static LIST_HEAD(clocks);
+static DEFINE_MUTEX(clocks_mutex);
+
+/*-------------------------------------------------------------------------
+ * Standard clock functions defined in include/linux/clk.h
+ *-------------------------------------------------------------------------*/
+
+/*
+ * Retrieve a clock by name.
+ *
+ * Note that we first try to use device id on the bus
+ * and clock name. If this fails, we try to use "<name>.<id>". If this fails,
+ * we try to use clock name only.
+ * The reference count to the clock's module owner ref count is incremented.
+ */
+struct clk *clk_get(struct device *dev, const char *id)
+{
+	struct clk *p, *clk = ERR_PTR(-ENOENT);
+	int idno;
+	const char *str;
+
+	if (id == NULL)
+		return clk;
+
+	if (dev == NULL || dev->bus != &platform_bus_type)
+		idno = -1;
+	else
+		idno = to_platform_device(dev)->id;
+
+	mutex_lock(&clocks_mutex);
+
+	list_for_each_entry(p, &clocks, node) {
+		if (p->id == idno &&
+		    strcmp(id, p->name) == 0 && try_module_get(p->owner)) {
+			clk = p;
+			goto found;
+		}
+	}
+
+	str = strrchr(id, '.');
+	if (str) {
+		int cnt = str - id;
+		str++;
+		idno = simple_strtol(str, NULL, 10);
+		list_for_each_entry(p, &clocks, node) {
+			if (p->id == idno &&
+			    strlen(p->name) == cnt &&
+			    strncmp(id, p->name, cnt) == 0 &&
+			    try_module_get(p->owner)) {
+				clk = p;
+				goto found;
+			}
+		}
+	}
+
+	list_for_each_entry(p, &clocks, node) {
+		if (strcmp(id, p->name) == 0 && try_module_get(p->owner)) {
+			clk = p;
+			goto found;
+		}
+	}
+
+	printk(KERN_WARNING "clk: Unable to get requested clock: %s\n", id);
+
+found:
+	mutex_unlock(&clocks_mutex);
+
+	return clk;
+}
+EXPORT_SYMBOL(clk_get);
+
+static void __clk_disable(struct clk *clk)
+{
+	if (clk == NULL || IS_ERR(clk))
+		return;
+
+	__clk_disable(clk->parent);
+	__clk_disable(clk->secondary);
+
+	if (!(--clk->usecount) && clk->disable)
+		clk->disable(clk);
+}
+
+static int __clk_enable(struct clk *clk)
+{
+	if (clk == NULL || IS_ERR(clk))
+		return -EINVAL;
+
+	__clk_enable(clk->parent);
+	__clk_enable(clk->secondary);
+
+	if (clk->usecount++ == 0 && clk->enable)
+		clk->enable(clk);
+
+	return 0;
+}
+
+/* This function increments the reference count on the clock and enables the
+ * clock if not already enabled. The parent clock tree is recursively enabled
+ */
+int clk_enable(struct clk *clk)
+{
+	int ret = 0;
+
+	if (clk == NULL || IS_ERR(clk))
+		return -EINVAL;
+
+	mutex_lock(&clocks_mutex);
+	ret = __clk_enable(clk);
+	mutex_unlock(&clocks_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL(clk_enable);
+
+/* This function decrements the reference count on the clock and disables
+ * the clock when reference count is 0. The parent clock tree is
+ * recursively disabled
+ */
+void clk_disable(struct clk *clk)
+{
+	if (clk == NULL || IS_ERR(clk))
+		return;
+
+	mutex_lock(&clocks_mutex);
+	__clk_disable(clk);
+	mutex_unlock(&clocks_mutex);
+}
+EXPORT_SYMBOL(clk_disable);
+
+/* Retrieve the *current* clock rate. If the clock itself
+ * does not provide a special calculation routine, ask
+ * its parent and so on, until one is able to return
+ * a valid clock rate
+ */
+unsigned long clk_get_rate(struct clk *clk)
+{
+	if (clk == NULL || IS_ERR(clk))
+		return 0UL;
+
+	if (clk->get_rate)
+		return clk->get_rate(clk);
+
+	return clk_get_rate(clk->parent);
+}
+EXPORT_SYMBOL(clk_get_rate);
+
+/* Decrement the clock's module reference count */
+void clk_put(struct clk *clk)
+{
+	if (clk && !IS_ERR(clk))
+		module_put(clk->owner);
+}
+EXPORT_SYMBOL(clk_put);
+
+/* Round the requested clock rate to the nearest supported
+ * rate that is less than or equal to the requested rate.
+ * This is dependent on the clock's current parent.
+ */
+long clk_round_rate(struct clk *clk, unsigned long rate)
+{
+	if (clk == NULL || IS_ERR(clk) || !clk->round_rate)
+		return 0;
+
+	return clk->round_rate(clk, rate);
+}
+EXPORT_SYMBOL(clk_round_rate);
+
+/* Set the clock to the requested clock rate. The rate must
+ * match a supported rate exactly based on what clk_round_rate returns
+ */
+int clk_set_rate(struct clk *clk, unsigned long rate)
+{
+	int ret = -EINVAL;
+
+	if (clk == NULL || IS_ERR(clk) || clk->set_rate == NULL || rate == 0)
+		return ret;
+
+	mutex_lock(&clocks_mutex);
+	ret = clk->set_rate(clk, rate);
+	mutex_unlock(&clocks_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL(clk_set_rate);
+
+/* Set the clock's parent to another clock source */
+int clk_set_parent(struct clk *clk, struct clk *parent)
+{
+	int ret = -EINVAL;
+
+	if (clk == NULL || IS_ERR(clk) || parent == NULL ||
+	    IS_ERR(parent) || clk->set_parent == NULL)
+		return ret;
+
+	mutex_lock(&clocks_mutex);
+	ret = clk->set_parent(clk, parent);
+	if (ret == 0)
+		clk->parent = parent;
+	mutex_unlock(&clocks_mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL(clk_set_parent);
+
+/* Retrieve the clock's parent clock source */
+struct clk *clk_get_parent(struct clk *clk)
+{
+	struct clk *ret = NULL;
+
+	if (clk == NULL || IS_ERR(clk))
+		return ret;
+
+	return clk->parent;
+}
+EXPORT_SYMBOL(clk_get_parent);
+
+/*
+ * Add a new clock to the clock tree.
+ */
+int clk_register(struct clk *clk)
+{
+	if (clk == NULL || IS_ERR(clk))
+		return -EINVAL;
+
+	mutex_lock(&clocks_mutex);
+	list_add(&clk->node, &clocks);
+	mutex_unlock(&clocks_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL(clk_register);
+
+/* Remove a clock from the clock tree */
+void clk_unregister(struct clk *clk)
+{
+	if (clk == NULL || IS_ERR(clk))
+		return;
+
+	mutex_lock(&clocks_mutex);
+	list_del(&clk->node);
+	mutex_unlock(&clocks_mutex);
+}
+EXPORT_SYMBOL(clk_unregister);
+
+#ifdef CONFIG_PROC_FS
+static int mxc_clock_read_proc(char *page, char **start, off_t off,
+				int count, int *eof, void *data)
+{
+	struct clk *clkp;
+	char *p = page;
+	int len;
+
+	list_for_each_entry(clkp, &clocks, node) {
+		p += sprintf(p, "%s-%d:\t\t%lu, %d", clkp->name, clkp->id,
+				clk_get_rate(clkp), clkp->usecount);
+		if (clkp->parent)
+			p += sprintf(p, ", %s-%d\n", clkp->parent->name,
+				     clkp->parent->id);
+		else
+			p += sprintf(p, "\n");
+	}
+
+	len = (p - page) - off;
+	if (len < 0)
+		len = 0;
+
+	*eof = (len <= count) ? 1 : 0;
+	*start = page + off;
+
+	return len;
+}
+
+static int __init mxc_setup_proc_entry(void)
+{
+	struct proc_dir_entry *res;
+
+	res = create_proc_read_entry("cpu/clocks", 0, NULL,
+				     mxc_clock_read_proc, NULL);
+	if (!res) {
+		printk(KERN_ERR "Failed to create proc/cpu/clocks\n");
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+late_initcall(mxc_setup_proc_entry);
+#endif

include/asm-arm/arch-mxc/clock.h

···
+/*
+ * Copyright 2005-2007 Freescale Semiconductor, Inc. All Rights Reserved.
+ * Copyright 2008 Juergen Beisert, [e-mail]
+ *
+ * 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., 51 Franklin Street, Fifth Floor, Boston,
+ * MA  02110-1301, USA.
+ */
+
+#ifndef __ASM_ARCH_MXC_CLOCK_H__
+#define __ASM_ARCH_MXC_CLOCK_H__
+
+#ifndef __ASSEMBLY__
+#include <linux/list.h>
+
+struct module;
+
+struct clk {
+	struct list_head node;
+	struct module *owner;
+	const char *name;
+	int id;
+	/* Source clock this clk depends on */
+	struct clk *parent;
+	/* Secondary clock to enable/disable with this clock */
+	struct clk *secondary;
+	/* Reference count of clock enable/disable */
+	__s8 usecount;
+	/* Register bit position for clock's enable/disable control. */
+	u8 enable_shift;
+	/* Register address for clock's enable/disable control. */
+	u32 enable_reg;
+	u32 flags;
+	/* get the current clock rate (always a fresh value) */
+	unsigned long (*get_rate) (struct clk *);
+	/* Function ptr to set the clock to a new rate. The rate must match a
+	   supported rate returned from round_rate. Leave blank if clock is not
+	   programmable */
+	int (*set_rate) (struct clk *, unsigned long);
+	/* Function ptr to round the requested clock rate to the nearest
+	   supported rate that is less than or equal to the requested rate. */
+	unsigned long (*round_rate) (struct clk *, unsigned long);
+	/* Function ptr to enable the clock. Leave blank if clock can not
+	   be gated. */
+	int (*enable) (struct clk *);
+	/* Function ptr to disable the clock. Leave blank if clock can not
+	   be gated. */
+	void (*disable) (struct clk *);
+	/* Function ptr to set the parent clock of the clock. */
+	int (*set_parent) (struct clk *, struct clk *);
+};
+
+int clk_register(struct clk *clk);
+void clk_unregister(struct clk *clk);
+
+#endif /* __ASSEMBLY__ */
+#endif /* __ASM_ARCH_MXC_CLOCK_H__ */