1 files changed, 226 insertions, 125 deletions

diff --git a/arch/arm/mach-tegra/clock.c b/arch/arm/mach-tegra/clock.c
index 8fd96bfb0cde..aff4c5b8c378 100644
--- a/arch/arm/mach-tegra/clock.c
+++ b/arch/arm/mach-tegra/clock.c
@@ -18,83 +18,117 @@
 
 #include <linux/kernel.h>
 #include <linux/clk.h>
-#include <linux/list.h>
+#include <linux/clkdev.h>
+#include <linux/debugfs.h>
+#include <linux/delay.h>
 #include <linux/init.h>
+#include <linux/list.h>
 #include <linux/module.h>
-#include <linux/debugfs.h>
-#include <linux/slab.h>
+#include <linux/sched.h>
 #include <linux/seq_file.h>
-#include <linux/clkdev.h>
+#include <linux/slab.h>
+
+#include <mach/clk.h>
 
 #include "board.h"
 #include "clock.h"
 
+/*
+ * Locking:
+ *
+ * Each struct clk has a spinlock.
+ *
+ * To avoid AB-BA locking problems, locks must always be traversed from child
+ * clock to parent clock.  For example, when enabling a clock, the clock's lock
+ * is taken, and then clk_enable is called on the parent, which take's the
+ * parent clock's lock.  There is one exceptions to this ordering: When dumping
+ * the clock tree through debugfs.  In this case, clk_lock_all is called,
+ * which attemps to iterate through the entire list of clocks and take every
+ * clock lock.  If any call to spin_trylock fails, all locked clocks are
+ * unlocked, and the process is retried.  When all the locks are held,
+ * the only clock operation that can be called is clk_get_rate_all_locked.
+ *
+ * Within a single clock, no clock operation can call another clock operation
+ * on itself, except for clk_get_rate_locked and clk_set_rate_locked.  Any
+ * clock operation can call any other clock operation on any of it's possible
+ * parents.
+ *
+ * An additional mutex, clock_list_lock, is used to protect the list of all
+ * clocks.
+ *
+ * The clock operations must lock internally to protect against
+ * read-modify-write on registers that are shared by multiple clocks
+ */
+static DEFINE_MUTEX(clock_list_lock);
 static LIST_HEAD(clocks);
 
-static DEFINE_SPINLOCK(clock_lock);
 struct clk *tegra_get_clock_by_name(const char *name)
 {
         struct clk *c;
         struct clk *ret = NULL;
-        unsigned long flags;
-        spin_lock_irqsave(&clock_lock, flags);
+        mutex_lock(&clock_list_lock);
         list_for_each_entry(c, &clocks, node) {
                 if (strcmp(c->name, name) == 0) {
                         ret = c;
                         break;
                 }
         }
-        spin_unlock_irqrestore(&clock_lock, flags);
+        mutex_unlock(&clock_list_lock);
         return ret;
 }
 
-static void clk_recalculate_rate(struct clk *c)
+/* Must be called with c->spinlock held */
+static unsigned long clk_predict_rate_from_parent(struct clk *c, struct clk *p)
 {
         u64 rate;
 
-        if (!c->parent)
-                return;
-
-        rate = c->parent->rate;
+        rate = clk_get_rate(p);
 
         if (c->mul != 0 && c->div != 0) {
-                rate = rate * c->mul;
+                rate *= c->mul;
                 do_div(rate, c->div);
         }
 
-        if (rate > c->max_rate)
-                pr_warn("clocks: Set clock %s to rate %llu, max is %lu\n",
-                        c->name, rate, c->max_rate);
-
-        c->rate = rate;
+        return rate;
 }
 
-int clk_reparent(struct clk *c, struct clk *parent)
+/* Must be called with c->spinlock held */
+unsigned long clk_get_rate_locked(struct clk *c)
 {
-        c->parent = parent;
-        list_del(&c->sibling);
-        list_add_tail(&c->sibling, &parent->children);
-        return 0;
-}
+        unsigned long rate;
 
-static void propagate_rate(struct clk *c)
-{
-        struct clk *clkp;
+        if (c->parent)
+                rate = clk_predict_rate_from_parent(c, c->parent);
+        else
+                rate = c->rate;
 
-        list_for_each_entry(clkp, &c->children, sibling) {
-                clk_recalculate_rate(clkp);
-                propagate_rate(clkp);
-        }
+        return rate;
 }
 
-void clk_init(struct clk *c)
+unsigned long clk_get_rate(struct clk *c)
 {
         unsigned long flags;
+        unsigned long rate;
 
-        spin_lock_irqsave(&clock_lock, flags);
+        spin_lock_irqsave(&c->spinlock, flags);
 
-        INIT_LIST_HEAD(&c->children);
-        INIT_LIST_HEAD(&c->sibling);
+        rate = clk_get_rate_locked(c);
+
+        spin_unlock_irqrestore(&c->spinlock, flags);
+
+        return rate;
+}
+EXPORT_SYMBOL(clk_get_rate);
+
+int clk_reparent(struct clk *c, struct clk *parent)
+{
+        c->parent = parent;
+        return 0;
+}
+
+void clk_init(struct clk *c)
+{
+        spin_lock_init(&c->spinlock);
 
         if (c->ops && c->ops->init)
                 c->ops->init(c);
@@ -108,33 +142,31 @@ void clk_init(struct clk *c)
                         c->state = ON;
         }
 
-        clk_recalculate_rate(c);
-
+        mutex_lock(&clock_list_lock);
         list_add(&c->node, &clocks);
-
-        if (c->parent)
-                list_add_tail(&c->sibling, &c->parent->children);
-
-        spin_unlock_irqrestore(&clock_lock, flags);
+        mutex_unlock(&clock_list_lock);
 }
 
-int clk_enable_locked(struct clk *c)
+int clk_enable(struct clk *c)
 {
-        int ret;
+        int ret = 0;
+        unsigned long flags;
+
+        spin_lock_irqsave(&c->spinlock, flags);
 
         if (c->refcnt == 0) {
                 if (c->parent) {
-                        ret = clk_enable_locked(c->parent);
+                        ret = clk_enable(c->parent);
                         if (ret)
-                                return ret;
+                                goto out;
                 }
 
                 if (c->ops && c->ops->enable) {
                         ret = c->ops->enable(c);
                         if (ret) {
                                 if (c->parent)
-                                        clk_disable_locked(c->parent);
-                                return ret;
+                                        clk_disable(c->parent);
+                                goto out;
                         }
                         c->state = ON;
 #ifdef CONFIG_DEBUG_FS
@@ -143,27 +175,21 @@ int clk_enable_locked(struct clk *c)
                 }
         }
         c->refcnt++;
-
-        return 0;
+out:
+        spin_unlock_irqrestore(&c->spinlock, flags);
+        return ret;
 }
+EXPORT_SYMBOL(clk_enable);
 
-int clk_enable(struct clk *c)
+void clk_disable(struct clk *c)
 {
-        int ret;
         unsigned long flags;
 
-        spin_lock_irqsave(&clock_lock, flags);
-        ret = clk_enable_locked(c);
-        spin_unlock_irqrestore(&clock_lock, flags);
+        spin_lock_irqsave(&c->spinlock, flags);
 
-        return ret;
-}
-EXPORT_SYMBOL(clk_enable);
-
-void clk_disable_locked(struct clk *c)
-{
         if (c->refcnt == 0) {
                 WARN(1, "Attempting to disable clock %s with refcnt 0", c->name);
+                spin_unlock_irqrestore(&c->spinlock, flags);
                 return;
         }
         if (c->refcnt == 1) {
@@ -171,49 +197,39 @@ void clk_disable_locked(struct clk *c)
                         c->ops->disable(c);
 
                 if (c->parent)
-                        clk_disable_locked(c->parent);
+                        clk_disable(c->parent);
 
                 c->state = OFF;
         }
         c->refcnt--;
-}
 
-void clk_disable(struct clk *c)
-{
-        unsigned long flags;
-
-        spin_lock_irqsave(&clock_lock, flags);
-        clk_disable_locked(c);
-        spin_unlock_irqrestore(&clock_lock, flags);
+        spin_unlock_irqrestore(&c->spinlock, flags);
 }
 EXPORT_SYMBOL(clk_disable);
 
-int clk_set_parent_locked(struct clk *c, struct clk *parent)
+int clk_set_parent(struct clk *c, struct clk *parent)
 {
         int ret;
+        unsigned long flags;
+        unsigned long new_rate;
+        unsigned long old_rate;
 
-        if (!c->ops || !c->ops->set_parent)
-                return -ENOSYS;
+        spin_lock_irqsave(&c->spinlock, flags);
 
-        ret = c->ops->set_parent(c, parent);
-
-        if (ret)
-                return ret;
-
-        clk_recalculate_rate(c);
+        if (!c->ops || !c->ops->set_parent) {
+                ret = -ENOSYS;
+                goto out;
+        }
 
-        propagate_rate(c);
+        new_rate = clk_predict_rate_from_parent(c, parent);
+        old_rate = clk_get_rate_locked(c);
 
-        return 0;
-}
+        ret = c->ops->set_parent(c, parent);
+        if (ret)
+                goto out;
 
-int clk_set_parent(struct clk *c, struct clk *parent)
-{
-        int ret;
-        unsigned long flags;
-        spin_lock_irqsave(&clock_lock, flags);
-        ret = clk_set_parent_locked(c, parent);
-        spin_unlock_irqrestore(&clock_lock, flags);
+out:
+        spin_unlock_irqrestore(&c->spinlock, flags);
         return ret;
 }
 EXPORT_SYMBOL(clk_set_parent);
@@ -226,62 +242,75 @@ EXPORT_SYMBOL(clk_get_parent);
 
 int clk_set_rate_locked(struct clk *c, unsigned long rate)
 {
-        int ret;
-
-        if (rate > c->max_rate)
-                rate = c->max_rate;
-
         if (!c->ops || !c->ops->set_rate)
                 return -ENOSYS;
 
-        ret = c->ops->set_rate(c, rate);
-
-        if (ret)
-                return ret;
-
-        clk_recalculate_rate(c);
-
-        propagate_rate(c);
+        if (rate > c->max_rate)
+                rate = c->max_rate;
 
-        return 0;
+        return c->ops->set_rate(c, rate);
 }
 
 int clk_set_rate(struct clk *c, unsigned long rate)
 {
-        int ret = 0;
+        int ret;
         unsigned long flags;
 
-        spin_lock_irqsave(&clock_lock, flags);
+        spin_lock_irqsave(&c->spinlock, flags);
+
         ret = clk_set_rate_locked(c, rate);
-        spin_unlock_irqrestore(&clock_lock, flags);
+
+        spin_unlock_irqrestore(&c->spinlock, flags);
 
         return ret;
 }
 EXPORT_SYMBOL(clk_set_rate);
 
-unsigned long clk_get_rate(struct clk *c)
-{
-        unsigned long flags;
-        unsigned long ret;
 
-        spin_lock_irqsave(&clock_lock, flags);
+/* Must be called with clocks lock and all indvidual clock locks held */
+unsigned long clk_get_rate_all_locked(struct clk *c)
+{
+        u64 rate;
+        int mul = 1;
+        int div = 1;
+        struct clk *p = c;
+
+        while (p) {
+                c = p;
+                if (c->mul != 0 && c->div != 0) {
+                        mul *= c->mul;
+                        div *= c->div;
+                }
+                p = c->parent;
+        }
 
-        ret = c->rate;
+        rate = c->rate;
+        rate *= mul;
+        do_div(rate, div);
 
-        spin_unlock_irqrestore(&clock_lock, flags);
-        return ret;
+        return rate;
 }
-EXPORT_SYMBOL(clk_get_rate);
 
 long clk_round_rate(struct clk *c, unsigned long rate)
 {
-        if (!c->ops || !c->ops->round_rate)
-                return -ENOSYS;
+        unsigned long flags;
+        long ret;
+
+        spin_lock_irqsave(&c->spinlock, flags);
+
+        if (!c->ops || !c->ops->round_rate) {
+                ret = -ENOSYS;
+                goto out;
+        }
 
         if (rate > c->max_rate)
                 rate = c->max_rate;
 
-        return c->ops->round_rate(c, rate);
+        ret = c->ops->round_rate(c, rate);
+
+out:
+        spin_unlock_irqrestore(&c->spinlock, flags);
+        return ret;
 }
 EXPORT_SYMBOL(clk_round_rate);
 
@@ -364,13 +393,75 @@ void __init tegra_init_clock(void)
 }
 
 #ifdef CONFIG_DEBUG_FS
+
+static int __clk_lock_all_spinlocks(void)
+{
+        struct clk *c;
+
+        list_for_each_entry(c, &clocks, node)
+                if (!spin_trylock(&c->spinlock))
+                        goto unlock_spinlocks;
+
+        return 0;
+
+unlock_spinlocks:
+        list_for_each_entry_continue_reverse(c, &clocks, node)
+                spin_unlock(&c->spinlock);
+
+        return -EAGAIN;
+}
+
+static void __clk_unlock_all_spinlocks(void)
+{
+        struct clk *c;
+
+        list_for_each_entry_reverse(c, &clocks, node)
+                spin_unlock(&c->spinlock);
+}
+
+/*
+ * This function retries until it can take all locks, and may take
+ * an arbitrarily long time to complete.
+ * Must be called with irqs enabled, returns with irqs disabled
+ * Must be called with clock_list_lock held
+ */
+static void clk_lock_all(void)
+{
+        int ret;
+retry:
+        local_irq_disable();
+
+        ret = __clk_lock_all_spinlocks();
+        if (ret)
+                goto failed_spinlocks;
+
+        /* All locks taken successfully, return */
+        return;
+
+failed_spinlocks:
+        local_irq_enable();
+        yield();
+        goto retry;
+}
+
+/*
+ * Unlocks all clocks after a clk_lock_all
+ * Must be called with irqs disabled, returns with irqs enabled
+ * Must be called with clock_list_lock held
+ */
+static void clk_unlock_all(void)
+{
+        __clk_unlock_all_spinlocks();
+
+        local_irq_enable();
+}
+
 static struct dentry *clk_debugfs_root;
 
 
 static void clock_tree_show_one(struct seq_file *s, struct clk *c, int level)
 {
         struct clk *child;
-        struct clk *safe;
         const char *state = "uninit";
         char div[8] = {0};
 
@@ -401,8 +492,12 @@ static void clock_tree_show_one(struct seq_file *s, struct clk *c, int level)
                 c->rate > c->max_rate ? '!' : ' ',
                 !c->set ? '*' : ' ',
                 30 - level * 3, c->name,
-                state, c->refcnt, div, c->rate);
-        list_for_each_entry_safe(child, safe, &c->children, sibling) {
+                state, c->refcnt, div, clk_get_rate_all_locked(c));
+
+        list_for_each_entry(child, &clocks, node) {
+                if (child->parent != c)
+                        continue;
+
                 clock_tree_show_one(s, child, level + 1);
         }
 }
@@ -410,14 +505,20 @@ static void clock_tree_show_one(struct seq_file *s, struct clk *c, int level)
 static int clock_tree_show(struct seq_file *s, void *data)
 {
         struct clk *c;
-        unsigned long flags;
         seq_printf(s, "   clock                          state  ref div      rate\n");
         seq_printf(s, "--------------------------------------------------------------\n");
-        spin_lock_irqsave(&clock_lock, flags);
+
+        mutex_lock(&clock_list_lock);
+
+        clk_lock_all();
+
         list_for_each_entry(c, &clocks, node)
                 if (c->parent == NULL)
                         clock_tree_show_one(s, c, 0);
-        spin_unlock_irqrestore(&clock_lock, flags);
+
+        clk_unlock_all();
+
+        mutex_unlock(&clock_list_lock);
         return 0;
 }