[PATCH v7 3/5] clk: Supply the critical clock {init, enable, disable} framework

Lee Jones
2015-07-22T13:19:46Z

These new API calls will firstly provide a mechanisms to tag a clock as
critical and secondly allow any knowledgeable driver to (un)gate clocks,
even if they are marked as critical.

Suggested-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
drivers/clk/clk.c | 45 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/clk-provider.h | 2 ++
include/linux/clk.h | 30 +++++++++++++++++++++++++++++
3 files changed, 77 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 61c3fc5..486b1da 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -46,6 +46,21 @@ static struct clk_core *clk_core_lookup(const char *name);

/*** private data structures ***/

+/**
+ * struct critical - Provides 'play' over critical clocks. A clock can be
+ * marked as critical, meaning that it should not be
+ * disabled. However, if a driver which is aware of the
+ * critical behaviour wants to control it, it can do so
+ * using clk_enable_critical() and clk_disable_critical().
+ *
+ * @enabled Is clock critical? Once set, doesn't change
+ * @leave_on Self explanatory. Can be disabled by knowledgeable drivers
+ */
+struct critical {
+ bool enabled;
+ bool leave_on;
+};
+
struct clk_core {
const char *name;
const struct clk_ops *ops;
@@ -75,6 +90,7 @@ struct clk_core {
struct dentry *dentry;
#endif
struct kref ref;
+ struct critical critical;
};

struct clk {
@@ -995,6 +1011,10 @@ static void clk_core_disable(struct clk_core *clk)
if (WARN_ON(clk->enable_count == 0))
return;

+ /* Refuse to turn off a critical clock */
+ if (clk->enable_count == 1 && clk->critical.leave_on)
+ return;
+
if (--clk->enable_count > 0)
return;

@@ -1037,6 +1057,13 @@ void clk_disable(struct clk *clk)
}
EXPORT_SYMBOL_GPL(clk_disable);

+void clk_disable_critical(struct clk *clk)
+{
+ clk->core->critical.leave_on = false;
+ clk_disable(clk);
+}
+EXPORT_SYMBOL_GPL(clk_disable_critical);
+
static int clk_core_enable(struct clk_core *clk)
{
int ret = 0;
@@ -1100,6 +1127,15 @@ int clk_enable(struct clk *clk)
}
EXPORT_SYMBOL_GPL(clk_enable);

+int clk_enable_critical(struct clk *clk)
+{
+ if (clk->core->critical.enabled)
+ clk->core->critical.leave_on = true;
+
+ return clk_enable(clk);
+}
+EXPORT_SYMBOL_GPL(clk_enable_critical);
+
static unsigned long clk_core_round_rate_nolock(struct clk_core *clk,
unsigned long rate,
unsigned long min_rate,
@@ -2482,6 +2518,15 @@ fail_out:
}
EXPORT_SYMBOL_GPL(clk_register);

+void clk_init_critical(struct clk *clk)
+{
+ struct critical *critical = &clk->core->critical;
+
+ critical->enabled = true;
+ critical->leave_on = true;
+}
+EXPORT_SYMBOL_GPL(clk_init_critical);
+
/*
* Free memory allocated for a clock.
* Caller must hold prepare_lock.
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 5591ea7..15ef8c9 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -563,6 +563,8 @@ struct clk *devm_clk_register(struct device *dev, struct clk_hw *hw);
void clk_unregister(struct clk *clk);
void devm_clk_unregister(struct device *dev, struct clk *clk);

+void clk_init_critical(struct clk *clk);
+
/* helper functions */
const char *__clk_get_name(struct clk *clk);
struct clk_hw *__clk_get_hw(struct clk *clk);
diff --git a/include/linux/clk.h b/include/linux/clk.h
index 8381bbf..9807f3b 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -231,6 +231,19 @@ struct clk *devm_clk_get(struct device *dev, const char *id);
int clk_enable(struct clk *clk);

/**
+ * clk_enable_critical - inform the system when the clock source should be
+ * running, even if clock is critical.
+ * @clk: clock source
+ *
+ * If the clock can not be enabled/disabled, this should return success.
+ *
+ * May be called from atomic contexts.
+ *
+ * Returns success (0) or negative errno.
+ */
+int clk_enable_critical(struct clk *clk);
+
+/**
* clk_disable - inform the system when the clock source is no longer required.
* @clk: clock source
*
@@ -247,6 +260,23 @@ int clk_enable(struct clk *clk);
void clk_disable(struct clk *clk);

/**
+ * clk_disable_critical - inform the system when the clock source is no
+ * longer required, even if clock is critical.
+ * @clk: clock source
+ *
+ * Inform the system that a clock source is no longer required by
+ * a driver and may be shut down.
+ *
+ * May be called from atomic contexts.
+ *
+ * Implementation detail: if the clock source is shared between
+ * multiple drivers, clk_enable_critical() calls must be balanced
+ * by the same number of clk_disable_critical() calls for the clock
+ * source to be disabled.
+ */
+void clk_disable_critical(struct clk *clk);
+
+/**
* clk_get_rate - obtain the current clock rate (in Hz) for a clock source.
* This is only valid once the clock source has been enabled.
* @clk: clock source
--
1.9.1