Sometimes clocks can't accept their parent source turning off
while the source is reprogrammed to a different rate. Most
notably some CPU clocks require a way to switch away from the
current PLL they're running on, reprogram that PLL to a new rate,
and then switch back to the PLL with the new rate once they're
done. Add a hook that drivers can implement allowing them to
return a 'safe parent' that they can switch their parent to while
the upstream source is reprogrammed.
Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
---
drivers/clk/clk.c | 53 ++++++++++++++++++++++++++++++++++++++------
include/linux/clk-private.h | 2 ++
include/linux/clk-provider.h | 1 +
3 files changed, 49 insertions(+), 7 deletions(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 255ec8c92919..b23e2b9c9102 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1368,6 +1368,7 @@ static void clk_calc_subtree(struct clk *clk, unsigned long new_rate,
struct clk *new_parent, u8 p_index)
{
struct clk *child;
+ struct clk *parent;
clk->new_rate = new_rate;
clk->new_parent = new_parent;
@@ -1377,6 +1378,17 @@ static void clk_calc_subtree(struct clk *clk, unsigned long new_rate,
if (new_parent && new_parent != clk->parent)
new_parent->new_child = clk;
+ if (clk->ops->get_safe_parent) {
+ parent = clk->ops->get_safe_parent(clk->hw);
+ if (parent) {
+ p_index = clk_fetch_parent_index(clk, parent);
+ clk->safe_parent_index = p_index;
+ clk->safe_parent = parent;
+ }
+ } else {
+ clk->safe_parent = NULL;
+ }
+
hlist_for_each_entry(child, &clk->children, child_node) {
child->new_rate = clk_recalc(child, new_rate);
clk_calc_subtree(child, child->new_rate, NULL, 0);
@@ -1459,14 +1471,42 @@ out:
static struct clk *clk_propagate_rate_change(struct clk *clk, unsigned long event)
{
struct clk *child, *tmp_clk, *fail_clk = NULL;
+ struct clk *old_parent;
int ret = NOTIFY_DONE;
- if (clk->rate == clk->new_rate)
+ if (clk->rate == clk->new_rate && event != POST_RATE_CHANGE)
return NULL;
+ switch (event) {
+ case PRE_RATE_CHANGE:
+ if (clk->safe_parent)
+ clk->ops->set_parent(clk->hw, clk->safe_parent_index);
+ break;
+ case POST_RATE_CHANGE:
+ if (clk->safe_parent) {
+ old_parent = __clk_set_parent_before(clk,
+ clk->new_parent);
+ if (clk->ops->set_rate_and_parent) {
+ clk->ops->set_rate_and_parent(clk->hw,
+ clk->new_rate,
+ clk->new_parent ?
+ clk->new_parent->rate : 0,
+ 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);
+ }
+ break;
+ }
+
if (clk->notifier_count) {
- ret = __clk_notify(clk, event, clk->rate, clk->new_rate);
- if (ret & NOTIFY_STOP_MASK)
+ if (event != POST_RATE_CHANGE)
+ ret = __clk_notify(clk, event, clk->rate,
+ clk->new_rate);
+ if (ret & NOTIFY_STOP_MASK && event != POST_RATE_CHANGE)
fail_clk = clk;
}
@@ -1508,7 +1548,8 @@ static void clk_change_rate(struct clk *clk)
else if (clk->parent)
best_parent_rate = clk->parent->rate;
- if (clk->new_parent && clk->new_parent != clk->parent) {
+ if (clk->new_parent && clk->new_parent != clk->parent &&
+ !clk->safe_parent) {
old_parent = __clk_set_parent_before(clk, clk->new_parent);
if (clk->ops->set_rate_and_parent) {
@@ -1528,9 +1569,6 @@ static void clk_change_rate(struct clk *clk)
clk->rate = clk_recalc(clk, best_parent_rate);
- 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) {
/* Skip children who will be reparented to another clock */
if (child->new_parent && child->new_parent != clk)
@@ -1604,6 +1642,7 @@ int clk_set_rate(struct clk *clk, unsigned long rate)
/* change the rates */
clk_change_rate(top);
+ clk_propagate_rate_change(top, POST_RATE_CHANGE);
out:
clk_prepare_unlock();
diff --git a/include/linux/clk-private.h b/include/linux/clk-private.h
index efbf70b9fd84..f48684af4d8f 100644
--- a/include/linux/clk-private.h
+++ b/include/linux/clk-private.h
@@ -38,8 +38,10 @@ struct clk {
struct clk **parents;
u8 num_parents;
u8 new_parent_index;
+ u8 safe_parent_index;
unsigned long rate;
unsigned long new_rate;
+ struct clk *safe_parent;
struct clk *new_parent;
struct clk *new_child;
unsigned long flags;
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 32d39613d217..6dec0b306336 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -170,6 +170,7 @@ struct clk_ops {
struct clk **best_parent_clk);
int (*set_parent)(struct clk_hw *hw, u8 index);
u8 (*get_parent)(struct clk_hw *hw);
+ struct clk *(*get_safe_parent)(struct clk_hw *hw);
int (*set_rate)(struct clk_hw *hw, unsigned long rate,
unsigned long parent_rate);
int (*set_rate_and_parent)(struct clk_hw *hw,
--
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