[PATCH 2/4] clk: Implement clk_set_rate

Implemenent clk_set_rate by adding a set_rate callback to clk_hw_ops,
and core code to handle propagation of rate changes up and down the
clock tree.

Signed-off-by: Jeremy Kerr <redacted>

---
?drivers/clk/clk.c ? | ? 74 ++++++++++++++++++++++++++++++++++++++++----
?include/linux/clk.h | ? 12 +++++++
?2 files changed, 80 insertions(+), 6 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index ad90a90..3a4d70e 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c

@@ -21,6 +21,8 @@ struct clk {

? ? ? ?unsigned int ? ? ? ? ? ?enable_count;
? ? ? ?unsigned int ? ? ? ? ? ?prepare_count;
? ? ? ?struct clk ? ? ? ? ? ? ?*parent;
+ ? ? ? struct hlist_head ? ? ? children;
+ ? ? ? struct hlist_node ? ? ? child_node;
? ? ? ?unsigned long ? ? ? ? ? rate;
?};

@@ -176,10 +178,61 @@ long clk_round_rate(struct clk *clk, unsigned long rate)

?}
?EXPORT_SYMBOL_GPL(clk_round_rate);

+/*
+ * clk_recalc_rates - Given a clock (with a recently updated clk->rate),
+ * ? ? notify its children that the rate may need to be recalculated, using
+ * ? ? ops->recalc_rate().
+ */
+static void clk_recalc_rates(struct clk *clk)
+{
+ ? ? ? struct hlist_node *tmp;
+ ? ? ? struct clk *child;
+
+ ? ? ? if (clk->ops->recalc_rate)
+ ? ? ? ? ? ? ? clk->rate = clk->ops->recalc_rate(clk->hw);
+
+ ? ? ? hlist_for_each_entry(child, tmp, &clk->children, child_node)
+ ? ? ? ? ? ? ? clk_recalc_rates(child);
+}
+
?int clk_set_rate(struct clk *clk, unsigned long rate)
?{
- ? ? ? /* not yet implemented */
- ? ? ? return -ENOSYS;
+ ? ? ? unsigned long parent_rate, new_rate;
+ ? ? ? int ret;
+
+ ? ? ? if (!clk->ops->set_rate)
+ ? ? ? ? ? ? ? return -ENOSYS;
+
+ ? ? ? new_rate = rate;
+
+ ? ? ? /* prevent racing with updates to the clock topology */
+ ? ? ? mutex_lock(&prepare_lock);
+
+propagate:
+ ? ? ? ret = clk->ops->set_rate(clk->hw, new_rate, &parent_rate);
+
+ ? ? ? if (ret < 0)
+ ? ? ? ? ? ? ? return ret;
+
+ ? ? ? /* ops->set_rate may require the parent's rate to change (to
+ ? ? ? ?* parent_rate), we need to propagate the set_rate call to the
+ ? ? ? ?* parent.
+ ? ? ? ?*/
+ ? ? ? if (ret == CLK_SET_RATE_PROPAGATE) {
+ ? ? ? ? ? ? ? new_rate = parent_rate;
+ ? ? ? ? ? ? ? clk = clk->parent;
+ ? ? ? ? ? ? ? goto propagate;
+ ? ? ? }
+
+ ? ? ? /* If successful (including propagation to the parent clock(s)),
+ ? ? ? ?* recalculate the rates of the clock, including children. ?We'll be
+ ? ? ? ?* calling this on the 'parent-most' clock that we propagated to.
+ ? ? ? ?*/
+ ? ? ? clk_recalc_rates(clk);
+
+ ? ? ? mutex_unlock(&prepare_lock);
+
+ ? ? ? return 0;
?}
?EXPORT_SYMBOL_GPL(clk_set_rate);

@@ -213,16 +266,25 @@ struct clk *clk_register(struct clk_hw_ops *ops, struct clk_hw *hw,

? ? ? ?clk->hw = hw;
? ? ? ?hw->clk = clk;

- ? ? ? /* Query the hardware for parent and initial rate */
+ ? ? ? /* Query the hardware for parent and initial rate. We may alter
+ ? ? ? ?* the clock topology, making this clock available from the parent's
+ ? ? ? ?* children list. So, we need to protect against concurrent
+ ? ? ? ?* accesses through set_rate
+ ? ? ? ?*/
+ ? ? ? mutex_lock(&prepare_lock);

- ? ? ? if (clk->ops->get_parent)
- ? ? ? ? ? ? ? /* We don't to lock against prepare/enable here, as
- ? ? ? ? ? ? ? ?* the clock is not yet accessible from anywhere */
+ ? ? ? if (clk->ops->get_parent) {
? ? ? ? ? ? ? ?clk->parent = clk->ops->get_parent(clk->hw);
+ ? ? ? ? ? ? ? if (clk->parent)
+ ? ? ? ? ? ? ? ? ? ? ? hlist_add_head(&clk->child_node,
+ ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? &clk->parent->children);
+ ? ? ? }

? ? ? ?if (clk->ops->recalc_rate)
? ? ? ? ? ? ? ?clk->rate = clk->ops->recalc_rate(clk->hw);

+ ? ? ? mutex_unlock(&prepare_lock);
+

? ? ? ?return clk;
?}

diff --git a/include/linux/clk.h b/include/linux/clk.h
index 93ff870..e0969d2 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h

@@ -58,6 +58,12 @@ struct clk_hw {

?* ? ? ? ? ? ? parent. Currently only called when the clock is first
?* ? ? ? ? ? ? registered.
?*
+ * @set_rate ? Change the rate of this clock. If this callback returns
+ * ? ? ? ? ? ? CLK_SET_RATE_PROPAGATE, the rate change will be propagated to
+ * ? ? ? ? ? ? the parent clock (which may propagate again). The requested
+ * ? ? ? ? ? ? rate of the parent is passed back from the callback in the
+ * ? ? ? ? ? ? second 'unsigned long *' argument.

+ *
?* The clk_enable/clk_disable and clk_prepare/clk_unprepare pairs allow
?* implementations to split any work between atomic (enable) and sleepable
?* (prepare) contexts. ?If a clock requires sleeping code to be turned on, this

@@ -76,9 +82,15 @@ struct clk_hw_ops {

? ? ? ?void ? ? ? ? ? ?(*disable)(struct clk_hw *);
? ? ? ?unsigned long ? (*recalc_rate)(struct clk_hw *);
? ? ? ?long ? ? ? ? ? ?(*round_rate)(struct clk_hw *, unsigned long);
+ ? ? ? int ? ? ? ? ? ? (*set_rate)(struct clk_hw *,
+ ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? unsigned long, unsigned long *);
? ? ? ?struct clk * ? ?(*get_parent)(struct clk_hw *);
?};

+enum {
+ ? ? ? CLK_SET_RATE_PROPAGATE = 1,
+};
+
?/**
?* clk_prepare - prepare clock for atomic enabling.
?*

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