Message-ID: <1366388904-13903-3-git-send-email-james.hogan@imgtec.com>
Date:	Fri, 19 Apr 2013 17:28:23 +0100
From:	James Hogan <james.hogan@...tec.com>
To:	Mike Turquette <mturquette@...aro.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
CC:	Stephen Boyd <sboyd@...eaurora.org>,
	James Hogan <james.hogan@...tec.com>
Subject: [PATCH v2 2/3] clk: add support for clock reparent on set_rate

Add core support to allow clock implementations to select the best
parent clock when rounding a rate, e.g. the one which can provide the
closest clock rate to that requested. This is by way of adding a new
clock op, determine_rate(), which is like round_rate() but has an extra
parameter to allow the clock implementation to optionally select a
different parent clock. The core then takes care of reparenting the
clock when setting the rate.

The parent change takes place with the help of two new private data
members. struct clk::new_parent specifies a clock's new parent (NULL
indicates no change), and struct clk::new_child specifies a clock's new
child (whose new_parent member points back to it). The purpose of these
are to allow correct walking of the future tree for notifications prior
to actually reparenting any clocks, specifically to skip child clocks
who are being reparented to another clock (they will be notified via the
new parent), and to include any new child clock. These pointers are set
by clk_calc_subtree(), and the new_child pointer gets cleared when a
child is actually reparented to avoid duplicate POST_RATE_CHANGE
notifications.

Each place where round_rate() is called, determine_rate is checked first
and called in preference, passing NULL to the new parent argument if not
needed (e.g. in __clk_round_rate). This restructures a few of the call
sites to simplify the logic into if/else blocks.

A new __clk_set_parent_no_recalc() is created similar to
clk_set_parent() but without calling __clk_recalc_rates(). This is for
clk_change_rate() to use, where rate recalculation and notifications are
already handled.

Signed-off-by: James Hogan <james.hogan@...tec.com>
---
 Documentation/clk.txt        |   4 ++
 drivers/clk/clk.c            | 146 ++++++++++++++++++++++++++++++-------------
 include/linux/clk-private.h  |   2 +
 include/linux/clk-provider.h |   7 +++
 4 files changed, 116 insertions(+), 43 deletions(-)

diff --git a/Documentation/clk.txt b/Documentation/clk.txt
index 1943fae..502c033 100644
--- a/Documentation/clk.txt
+++ b/Documentation/clk.txt
@@ -70,6 +70,10 @@ the operations defined in clk.h:
 						unsigned long parent_rate);
 		long		(*round_rate)(struct clk_hw *hw, unsigned long,
 						unsigned long *);
+		long		(*determine_rate)(struct clk_hw *hw,
+						unsigned long rate,
+						unsigned long *best_parent_rate,
+						struct clk **best_parent_clk);
 		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);
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 79d5deb..cc0e618 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -27,6 +27,8 @@ static HLIST_HEAD(clk_root_list);
 static HLIST_HEAD(clk_orphan_list);
 static LIST_HEAD(clk_notifier_list);
 
+static int __clk_set_parent_no_recalc(struct clk *clk, struct clk *parent);
+
 /***        debugfs support        ***/
 
 #ifdef CONFIG_COMMON_CLK_DEBUG
@@ -727,17 +729,20 @@ unsigned long __clk_round_rate(struct clk *clk, unsigned long rate)
 	if (!clk)
 		return 0;
 
-	if (!clk->ops->round_rate) {
-		if (clk->flags & CLK_SET_RATE_PARENT)
-			return __clk_round_rate(clk->parent, rate);
-		else
-			return clk->rate;
-	}
 
 	if (clk->parent)
 		parent_rate = clk->parent->rate;
 
-	return clk->ops->round_rate(clk->hw, rate, &parent_rate);
+	if (clk->ops->determine_rate)
+		return clk->ops->determine_rate(clk->hw, rate, &parent_rate,
+						NULL);
+	else if (clk->ops->round_rate)
+		return clk->ops->round_rate(clk->hw, rate, &parent_rate);
+	else if (clk->flags & CLK_SET_RATE_PARENT)
+		return __clk_round_rate(clk->parent, rate);
+	else
+		return clk->rate;
+
 }
 
 /**
@@ -906,18 +911,23 @@ out:
 	return ret;
 }
 
-static void clk_calc_subtree(struct clk *clk, unsigned long new_rate)
+static void clk_calc_subtree(struct clk *clk, unsigned long new_rate,
+			     struct clk *new_parent)
 {
 	struct clk *child;
 
 	clk->new_rate = new_rate;
+	clk->new_parent = new_parent;
+	clk->new_child = NULL;
+	if (new_parent && new_parent != clk->parent)
+		new_parent->new_child = clk;
 
 	hlist_for_each_entry(child, &clk->children, child_node) {
 		if (child->ops->recalc_rate)
 			child->new_rate = child->ops->recalc_rate(child->hw, new_rate);
 		else
 			child->new_rate = new_rate;
-		clk_calc_subtree(child, child->new_rate);
+		clk_calc_subtree(child, child->new_rate, NULL);
 	}
 }
 
@@ -928,6 +938,7 @@ static void clk_calc_subtree(struct clk *clk, unsigned long new_rate)
 static struct clk *clk_calc_new_rates(struct clk *clk, unsigned long rate)
 {
 	struct clk *top = clk;
+	struct clk *old_parent, *parent;
 	unsigned long best_parent_rate = 0;
 	unsigned long new_rate;
 
@@ -936,42 +947,43 @@ static struct clk *clk_calc_new_rates(struct clk *clk, unsigned long rate)
 		return NULL;
 
 	/* save parent rate, if it exists */
-	if (clk->parent)
-		best_parent_rate = clk->parent->rate;
-
-	/* never propagate up to the parent */
-	if (!(clk->flags & CLK_SET_RATE_PARENT)) {
-		if (!clk->ops->round_rate) {
-			clk->new_rate = clk->rate;
-			return NULL;
-		}
-		new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
+	parent = old_parent = clk->parent;
+	if (parent)
+		best_parent_rate = parent->rate;
+
+	/* find the closest rate and parent clk/rate */
+	if (clk->ops->determine_rate) {
+		new_rate = clk->ops->determine_rate(clk->hw, rate,
+						    &best_parent_rate,
+						    &parent);
+	} else if (clk->ops->round_rate) {
+		new_rate = clk->ops->round_rate(clk->hw, rate,
+						&best_parent_rate);
+	} else if (!parent || !(clk->flags & CLK_SET_RATE_PARENT)) {
+		/* pass-through clock without adjustable parent */
+		clk->new_rate = clk->rate;
+		return NULL;
+	} else {
+		/* pass-through clock with adjustable parent */
+		top = clk_calc_new_rates(parent, rate);
+		new_rate = parent->new_rate;
 		goto out;
 	}
 
-	/* need clk->parent from here on out */
-	if (!clk->parent) {
-		pr_debug("%s: %s has NULL parent\n", __func__, clk->name);
+	/* some clocks must be gated to change parent */
+	if (parent != old_parent &&
+	    (clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count) {
+		pr_debug("%s: %s not gated but wants to reparent\n",
+			 __func__, clk->name);
 		return NULL;
 	}
 
-	if (!clk->ops->round_rate) {
-		top = clk_calc_new_rates(clk->parent, rate);
-		new_rate = clk->parent->new_rate;
-
-		goto out;
-	}
-
-	new_rate = clk->ops->round_rate(clk->hw, rate, &best_parent_rate);
-
-	if (best_parent_rate != clk->parent->rate) {
-		top = clk_calc_new_rates(clk->parent, best_parent_rate);
-
-		goto out;
-	}
+	if ((clk->flags & CLK_SET_RATE_PARENT) && parent &&
+	    best_parent_rate != parent->rate)
+		top = clk_calc_new_rates(parent, best_parent_rate);
 
 out:
-	clk_calc_subtree(clk, new_rate);
+	clk_calc_subtree(clk, new_rate, parent);
 
 	return top;
 }
@@ -983,7 +995,7 @@ out:
  */
 static struct clk *clk_propagate_rate_change(struct clk *clk, unsigned long event)
 {
-	struct clk *child, *fail_clk = NULL;
+	struct clk *child, *tmp_clk, *fail_clk = NULL;
 	int ret = NOTIFY_DONE;
 
 	if (clk->rate == clk->new_rate)
@@ -996,9 +1008,19 @@ static struct clk *clk_propagate_rate_change(struct clk *clk, unsigned long even
 	}
 
 	hlist_for_each_entry(child, &clk->children, child_node) {
-		clk = clk_propagate_rate_change(child, event);
-		if (clk)
-			fail_clk = clk;
+		/* Skip children who will be reparented to another clock */
+		if (child->new_parent && child->new_parent != clk)
+			continue;
+		tmp_clk = clk_propagate_rate_change(child, event);
+		if (tmp_clk)
+			fail_clk = tmp_clk;
+	}
+
+	/* handle the new child who might not be in clk->children yet */
+	if (clk->new_child) {
+		tmp_clk = clk_propagate_rate_change(clk->new_child, event);
+		if (tmp_clk)
+			fail_clk = tmp_clk;
 	}
 
 	return fail_clk;
@@ -1016,6 +1038,10 @@ static void clk_change_rate(struct clk *clk)
 
 	old_rate = clk->rate;
 
+	/* set parent */
+	if (clk->new_parent && clk->new_parent != clk->parent)
+		__clk_set_parent_no_recalc(clk, clk->new_parent);
+
 	if (clk->parent)
 		best_parent_rate = clk->parent->rate;
 
@@ -1030,8 +1056,15 @@ static void clk_change_rate(struct clk *clk)
 	if (clk->notifier_count && old_rate != clk->rate)
 		__clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate);
 
-	hlist_for_each_entry(child, &clk->children, child_node)
+	hlist_for_each_entry(child, &clk->children, child_node) {
+		/* Skip children who will be reparented to another clock */
+		if (child->new_parent && child->new_parent != clk)
+			continue;
 		clk_change_rate(child);
+	}
+
+	if (clk->new_child)
+		clk_change_rate(clk->new_child);
 }
 
 /**
@@ -1169,7 +1202,7 @@ out:
 	return ret;
 }
 
-void __clk_reparent(struct clk *clk, struct clk *new_parent)
+void __clk_reparent_no_recalc(struct clk *clk, struct clk *new_parent)
 {
 #ifdef CONFIG_COMMON_CLK_DEBUG
 	struct dentry *d;
@@ -1179,6 +1212,9 @@ void __clk_reparent(struct clk *clk, struct clk *new_parent)
 	if (!clk || !new_parent)
 		return;
 
+	if (new_parent->new_child == clk)
+		new_parent->new_child = NULL;
+
 	hlist_del(&clk->child_node);
 
 	if (new_parent)
@@ -1206,6 +1242,11 @@ out:
 #endif
 
 	clk->parent = new_parent;
+}
+
+void __clk_reparent(struct clk *clk, struct clk *new_parent)
+{
+	__clk_reparent_no_recalc(clk, new_parent);
 
 	__clk_recalc_rates(clk, POST_RATE_CHANGE);
 }
@@ -1270,6 +1311,25 @@ out:
 	return ret;
 }
 
+static int __clk_set_parent_no_recalc(struct clk *clk, struct clk *parent)
+{
+	int ret = 0;
+
+	if (clk->parent == parent)
+		goto out;
+
+	/* only re-parent if the clock is not in use */
+	ret = __clk_set_parent(clk, parent);
+	if (ret)
+		goto out;
+
+	/* reparent, but don't propagate rate recalculation downstream */
+	__clk_reparent_no_recalc(clk, parent);
+
+out:
+	return ret;
+}
+
 /**
  * clk_set_parent - switch the parent of a mux clk
  * @clk: the mux clk whose input we are switching
diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h
index 9c7f580..0826a60 100644
--- a/include/linux/clk-private.h
+++ b/include/linux/clk-private.h
@@ -35,6 +35,8 @@ struct clk {
 	u8			num_parents;
 	unsigned long		rate;
 	unsigned long		new_rate;
+	struct clk		*new_parent;
+	struct clk		*new_child;
 	unsigned long		flags;
 	unsigned int		enable_count;
 	unsigned int		prepare_count;
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 4e0b634..5fe1d38 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -71,6 +71,10 @@ struct clk_hw;
  * @round_rate:	Given a target rate as input, returns the closest rate actually
  * 		supported by the clock.
  *
+ * @determine_rate: Given a target rate as input, returns the closest rate
+ *		actually supported by the clock, and optionally the parent clock
+ *		that should be used to provide the clock rate.
+ *
  * @get_parent:	Queries the hardware to determine the parent of a clock.  The
  * 		return value is a u8 which specifies the index corresponding to
  * 		the parent clock.  This index can be applied to either the
@@ -116,6 +120,9 @@ struct clk_ops {
 					unsigned long parent_rate);
 	long		(*round_rate)(struct clk_hw *hw, unsigned long,
 					unsigned long *);
+	long		(*determine_rate)(struct clk_hw *hw, unsigned long rate,
+					unsigned long *best_parent_rate,
+					struct clk **best_parent_clk);
 	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,
-- 
1.8.1.2


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