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authorJames Hogan <james.hogan@imgtec.com>2013-07-29 12:25:00 +0100
committerMike Turquette <mturquette@linaro.org>2013-08-19 12:27:17 -0700
commit71472c0c06cf9a3d1540762ea205654c584e3bc4 (patch)
tree22db34b3c7bc0d0053fcfac2c95d77adf09107de
parent4935b22c46ea5e2dc44ef0b72db50741649eb3a4 (diff)
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 some 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. This restructures a few of the call sites to simplify the logic into if/else blocks. Signed-off-by: James Hogan <james.hogan@imgtec.com> Reviewed-by: Stephen Boyd <sboyd@codeaurora.org> Cc: Mike Turquette <mturquette@linaro.org> Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Mike Turquette <mturquette@linaro.org>
-rw-r--r--Documentation/clk.txt46
-rw-r--r--drivers/clk/clk.c142
-rw-r--r--include/linux/clk-private.h3
-rw-r--r--include/linux/clk-provider.h7
4 files changed, 132 insertions, 66 deletions
diff --git a/Documentation/clk.txt b/Documentation/clk.txt
index 6f68ba0d1e01..3aeb5c440442 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);
@@ -179,26 +183,28 @@ mandatory, a cell marked as "n" implies that either including that
callback is invalid or otherwise unnecessary. Empty cells are either
optional or must be evaluated on a case-by-case basis.
- clock hardware characteristics
- -----------------------------------------------------------
- | gate | change rate | single parent | multiplexer | root |
- |------|-------------|---------------|-------------|------|
-.prepare | | | | | |
-.unprepare | | | | | |
- | | | | | |
-.enable | y | | | | |
-.disable | y | | | | |
-.is_enabled | y | | | | |
- | | | | | |
-.recalc_rate | | y | | | |
-.round_rate | | y | | | |
-.set_rate | | y | | | |
- | | | | | |
-.set_parent | | | n | y | n |
-.get_parent | | | n | y | n |
- | | | | | |
-.init | | | | | |
- -----------------------------------------------------------
+ clock hardware characteristics
+ -----------------------------------------------------------
+ | gate | change rate | single parent | multiplexer | root |
+ |------|-------------|---------------|-------------|------|
+.prepare | | | | | |
+.unprepare | | | | | |
+ | | | | | |
+.enable | y | | | | |
+.disable | y | | | | |
+.is_enabled | y | | | | |
+ | | | | | |
+.recalc_rate | | y | | | |
+.round_rate | | y [1] | | | |
+.determine_rate | | y [1] | | | |
+.set_rate | | y | | | |
+ | | | | | |
+.set_parent | | | n | y | n |
+.get_parent | | | n | y | n |
+ | | | | | |
+.init | | | | | |
+ -----------------------------------------------------------
+[1] either one of round_rate or determine_rate is required.
Finally, register your clock at run-time with a hardware-specific
registration function. This function simply populates struct clk_foo's
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 3d57cf64c9e7..f33f1ccf1b2f 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -889,21 +889,24 @@ EXPORT_SYMBOL_GPL(clk_enable);
unsigned long __clk_round_rate(struct clk *clk, unsigned long rate)
{
unsigned long parent_rate = 0;
+ struct clk *parent;
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);
+ parent = clk->parent;
+ if (parent)
+ parent_rate = parent->rate;
+
+ if (clk->ops->determine_rate)
+ return clk->ops->determine_rate(clk->hw, rate, &parent_rate,
+ &parent);
+ 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;
}
/**
@@ -1056,6 +1059,10 @@ static u8 clk_fetch_parent_index(struct clk *clk, struct clk *parent)
static void clk_reparent(struct clk *clk, struct clk *new_parent)
{
+ /* avoid duplicate POST_RATE_CHANGE notifications */
+ if (new_parent->new_child == clk)
+ new_parent->new_child = NULL;
+
hlist_del(&clk->child_node);
if (new_parent)
@@ -1176,18 +1183,25 @@ 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, u8 p_index)
{
struct clk *child;
clk->new_rate = new_rate;
+ clk->new_parent = new_parent;
+ clk->new_parent_index = p_index;
+ /* include clk in new parent's PRE_RATE_CHANGE notifications */
+ 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, 0);
}
}
@@ -1198,50 +1212,63 @@ 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;
+ u8 p_index = 0;
/* sanity */
if (IS_ERR_OR_NULL(clk))
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;
+ /* try finding the new parent index */
+ if (parent) {
+ p_index = clk_fetch_parent_index(clk, parent);
+ if (p_index == clk->num_parents) {
+ pr_debug("%s: clk %s can not be parent of clk %s\n",
+ __func__, parent->name, clk->name);
+ return NULL;
+ }
}
- 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, p_index);
return top;
}
@@ -1253,7 +1280,7 @@ 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)
@@ -1266,9 +1293,19 @@ 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;
@@ -1286,6 +1323,10 @@ 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(clk, clk->new_parent, clk->new_parent_index);
+
if (clk->parent)
best_parent_rate = clk->parent->rate;
@@ -1300,8 +1341,16 @@ 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);
+ }
+
+ /* handle the new child who might not be in clk->children yet */
+ if (clk->new_child)
+ clk_change_rate(clk->new_child);
}
/**
@@ -1552,8 +1601,9 @@ int __clk_init(struct device *dev, struct clk *clk)
/* check that clk_ops are sane. See Documentation/clk.txt */
if (clk->ops->set_rate &&
- !(clk->ops->round_rate && clk->ops->recalc_rate)) {
- pr_warning("%s: %s must implement .round_rate & .recalc_rate\n",
+ !((clk->ops->round_rate || clk->ops->determine_rate) &&
+ clk->ops->recalc_rate)) {
+ pr_warning("%s: %s must implement .round_rate or .determine_rate in addition to .recalc_rate\n",
__func__, clk->name);
ret = -EINVAL;
goto out;
diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h
index dd7adff76e81..8138c94409f3 100644
--- a/include/linux/clk-private.h
+++ b/include/linux/clk-private.h
@@ -33,8 +33,11 @@ struct clk {
const char **parent_names;
struct clk **parents;
u8 num_parents;
+ u8 new_parent_index;
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 a83409285a7f..4f525b37c6fd 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -79,6 +79,10 @@ 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
@@ -126,6 +130,9 @@ 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,