[PATCH v2 3/9] clk: Add set_rate_and_parent() op

Stephen Boyd
2013-10-02T19:07:21Z

Some of Qualcomm's clocks can change their parent and rate at the
same time with a single register write. Add support for this
hardware to the common clock framework by adding a new
set_rate_and_parent() op. When the clock framework determines
that both the parent and the rate are going to change during
clk_set_rate() it will call the .set_rate_and_parent() op if
available and fall back to calling .set_parent() followed by
.set_rate() otherwise.

Reviewed-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---
Documentation/clk.txt | 3 ++
drivers/clk/clk.c | 78 +++++++++++++++++++++++++++++++++-----------
include/linux/clk-provider.h | 15 +++++++++
3 files changed, 77 insertions(+), 19 deletions(-)

diff --git a/Documentation/clk.txt b/Documentation/clk.txt
index 3aeb5c4..79700ea 100644
--- a/Documentation/clk.txt
+++ b/Documentation/clk.txt
@@ -77,6 +77,9 @@ the operations defined in clk.h:
int (*set_parent)(struct clk_hw *hw, u8 index);
u8 (*get_parent)(struct clk_hw *hw);
int (*set_rate)(struct clk_hw *hw, unsigned long);
+ int (*set_rate_and_parent)(struct clk_hw *hw,
+ unsigned long rate,
+ unsigned long parent_rate, u8 index);
void (*init)(struct clk_hw *hw);
};

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 7e4519b..a814dd1 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1194,10 +1194,9 @@ static void clk_reparent(struct clk *clk, struct clk *new_parent)
clk->parent = new_parent;
}

-static int __clk_set_parent(struct clk *clk, struct clk *parent, u8 p_index)
+static struct clk *__clk_set_parent_before(struct clk *clk, struct clk *parent)
{
unsigned long flags;
- int ret = 0;
struct clk *old_parent = clk->parent;

/*
@@ -1228,6 +1227,34 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent, u8 p_index)
clk_reparent(clk, parent);
clk_enable_unlock(flags);

+ return old_parent;
+}
+
+static void __clk_set_parent_after(struct clk *clk, struct clk *parent,
+ struct clk *old_parent)
+{
+ /*
+ * Finish the migration of prepare state and undo the changes done
+ * for preventing a race with clk_enable().
+ */
+ if (clk->prepare_count) {
+ clk_disable(clk);
+ clk_disable(old_parent);
+ __clk_unprepare(old_parent);
+ }
+
+ /* update debugfs with new clk tree topology */
+ clk_debug_reparent(clk, parent);
+}
+
+static int __clk_set_parent(struct clk *clk, struct clk *parent, u8 p_index)
+{
+ unsigned long flags;
+ int ret = 0;
+ struct clk *old_parent;
+
+ old_parent = __clk_set_parent_before(clk, parent);
+
/* change clock input source */
if (parent && clk->ops->set_parent)
ret = clk->ops->set_parent(clk->hw, p_index);
@@ -1245,18 +1272,8 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent, u8 p_index)
return ret;
}

- /*
- * Finish the migration of prepare state and undo the changes done
- * for preventing a race with clk_enable().
- */
- if (clk->prepare_count) {
- clk_disable(clk);
- clk_disable(old_parent);
- __clk_unprepare(old_parent);
- }
+ __clk_set_parent_after(clk, parent, old_parent);

- /* update debugfs with new clk tree topology */
- clk_debug_reparent(clk, parent);
return 0;
}

@@ -1441,17 +1458,32 @@ static void clk_change_rate(struct clk *clk)
struct clk *child;
unsigned long old_rate;
unsigned long best_parent_rate = 0;
+ bool skip_set_rate = false;
+ struct clk *old_parent;

old_rate = clk->rate;

- /* set parent */
- if (clk->new_parent && clk->new_parent != clk->parent)
- __clk_set_parent(clk, clk->new_parent, clk->new_parent_index);
-
- if (clk->parent)
+ if (clk->new_parent)
+ best_parent_rate = clk->new_parent->rate;
+ else if (clk->parent)
best_parent_rate = clk->parent->rate;

- if (clk->ops->set_rate)
+ if (clk->new_parent && clk->new_parent != clk->parent) {
+ old_parent = __clk_set_parent_before(clk, clk->new_parent);
+
+ if (clk->ops->set_rate_and_parent) {
+ skip_set_rate = true;
+ clk->ops->set_rate_and_parent(clk->hw, clk->new_rate,
+ best_parent_rate,
+ clk->new_parent_index);
+ } else if (clk->ops->set_parent) {
+ clk->ops->set_parent(clk->hw, clk->new_parent_index);
+ }
+
+ __clk_set_parent_after(clk, clk->new_parent, old_parent);
+ }
+
+ if (!skip_set_rate && clk->ops->set_rate)
clk->ops->set_rate(clk->hw, clk->new_rate, best_parent_rate);

if (clk->ops->recalc_rate)
@@ -1743,6 +1775,14 @@ int __clk_init(struct device *dev, struct clk *clk)
goto out;
}

+ if (clk->ops->set_rate_and_parent &&
+ !(clk->ops->set_parent && clk->ops->set_rate)) {
+ pr_warn("%s: %s must implement .set_parent & .set_rate\n",
+ __func__, clk->name);
+ ret = -EINVAL;
+ goto out;
+ }
+
/* throw a WARN if any entries in parent_names are NULL */
for (i = 0; i < clk->num_parents; i++)
WARN(!clk->parent_names[i],
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 4087a9b..2bd6617 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -108,6 +108,18 @@ struct clk_hw;
* which is likely helpful for most .set_rate implementation.
* Returns 0 on success, -EERROR otherwise.
*
+ * @set_rate_and_parent: Change the rate and the parent of this clock. The
+ * requested rate is specified by the second argument, which
+ * should typically be the return of .round_rate call. The
+ * third argument gives the parent rate which is likely helpful
+ * for most .set_rate_and_parent implementation. The fourth
+ * argument gives the parent index. This callback is optional (and
+ * unnecessary) for clocks with 0 or 1 parents as well as
+ * for clocks that can tolerate switching the rate and the parent
+ * separately via calls to .set_parent and .set_rate.
+ * Returns 0 on success, -EERROR otherwise.
+ *
+ *
* 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 enabling a clock requires code that might sleep,
@@ -139,6 +151,9 @@ struct clk_ops {
u8 (*get_parent)(struct clk_hw *hw);
int (*set_rate)(struct clk_hw *hw, unsigned long,
unsigned long);
+ int (*set_rate_and_parent)(struct clk_hw *hw,
+ unsigned long rate,
+ unsigned long parent_rate, u8 index);
void (*init)(struct clk_hw *hw);
};