ARM: tegra: clock: Convert global lock to a lock per clock
Give each clock its own lock, and remove all lock traversals from
parent to child clocks to prevent AB-BA deadlocks.
This brings the locking in line with the common struct clk
patches and should make conversion simple.
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Colin Cross <ccross@android.com>
diff --git a/arch/arm/mach-tegra/clock.c b/arch/arm/mach-tegra/clock.c
index 8fd96bfb..aff4c5b8 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/init.h>
-#include <linux/module.h>
-#include <linux/debugfs.h>
-#include <linux/slab.h>
-#include <linux/seq_file.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/sched.h>
+#include <linux/seq_file.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;
}
+/* Must be called with c->spinlock held */
+unsigned long clk_get_rate_locked(struct clk *c)
+{
+ unsigned long rate;
+
+ if (c->parent)
+ rate = clk_predict_rate_from_parent(c, c->parent);
+ else
+ rate = c->rate;
+
+ return rate;
+}
+
+unsigned long clk_get_rate(struct clk *c)
+{
+ unsigned long flags;
+ unsigned long rate;
+
+ spin_lock_irqsave(&c->spinlock, flags);
+
+ 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;
- list_del(&c->sibling);
- list_add_tail(&c->sibling, &parent->children);
return 0;
}
-static void propagate_rate(struct clk *c)
-{
- struct clk *clkp;
-
- list_for_each_entry(clkp, &c->children, sibling) {
- clk_recalculate_rate(clkp);
- propagate_rate(clkp);
- }
-}
-
void clk_init(struct clk *c)
{
- unsigned long flags;
-
- spin_lock_irqsave(&clock_lock, flags);
-
- INIT_LIST_HEAD(&c->children);
- INIT_LIST_HEAD(&c->sibling);
+ spin_lock_init(&c->spinlock);
if (c->ops && c->ops->init)
c->ops->init(c);
@@ -108,33 +142,31 @@
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 @@
}
}
c->refcnt++;
-
- return 0;
-}
-
-int clk_enable(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);
-
+out:
+ spin_unlock_irqrestore(&c->spinlock, flags);
return ret;
}
EXPORT_SYMBOL(clk_enable);
-void clk_disable_locked(struct clk *c)
+void clk_disable(struct clk *c)
{
+ unsigned long flags;
+
+ spin_lock_irqsave(&c->spinlock, flags);
+
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 @@
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 ret;
-
- if (!c->ops || !c->ops->set_parent)
- return -ENOSYS;
-
- ret = c->ops->set_parent(c, parent);
-
- if (ret)
- return ret;
-
- clk_recalculate_rate(c);
-
- propagate_rate(c);
-
- return 0;
-}
-
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);
+ unsigned long new_rate;
+ unsigned long old_rate;
+
+ spin_lock_irqsave(&c->spinlock, flags);
+
+ if (!c->ops || !c->ops->set_parent) {
+ ret = -ENOSYS;
+ goto out;
+ }
+
+ new_rate = clk_predict_rate_from_parent(c, parent);
+ old_rate = clk_get_rate_locked(c);
+
+ ret = c->ops->set_parent(c, parent);
+ if (ret)
+ goto out;
+
+out:
+ spin_unlock_irqrestore(&c->spinlock, flags);
return ret;
}
EXPORT_SYMBOL(clk_set_parent);
@@ -226,62 +242,75 @@
int clk_set_rate_locked(struct clk *c, unsigned long rate)
{
- int ret;
+ if (!c->ops || !c->ops->set_rate)
+ return -ENOSYS;
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);
-
- 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)
+
+/* Must be called with clocks lock and all indvidual clock locks held */
+unsigned long clk_get_rate_all_locked(struct clk *c)
{
- unsigned long flags;
- unsigned long ret;
+ u64 rate;
+ int mul = 1;
+ int div = 1;
+ struct clk *p = c;
- spin_lock_irqsave(&clock_lock, flags);
+ 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 @@
}
#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 @@
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 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;
}