From: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
Sometimes clocks can't accept their parent source turning off
while the source is reprogrammed to a different rate. Most
notably 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' and 'safe frequency' that they can switch their
parent to while the upstream source is reprogrammed to support
this.
Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
Signed-off-by: Georgi Djakov <georgi.djakov@xxxxxxxxxx>
---
drivers/clk/clk.c | 73 +++++++++++++++++++++++++++++++++++++++---
include/linux/clk-provider.h | 2 ++
2 files changed, 70 insertions(+), 5 deletions(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 128ad748b682..df5f5b65833c 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -51,9 +51,13 @@ struct clk_core {
struct clk_core **parents;
u8 num_parents;
u8 new_parent_index;
+ u8 safe_parent_index;
unsigned long rate;
unsigned long req_rate;
+ unsigned long old_rate;
unsigned long new_rate;
+ unsigned long safe_freq;
+ struct clk_core *safe_parent;
struct clk_core *new_parent;
struct clk_core *new_child;
unsigned long flags;
@@ -1271,7 +1275,9 @@ out:
static void clk_calc_subtree(struct clk_core *core, unsigned long new_rate,
struct clk_core *new_parent, u8 p_index)
{
- struct clk_core *child;
+ struct clk_core *child, *parent;
+ struct clk_hw *parent_hw;
+ unsigned long safe_freq = 0;
core->new_rate = new_rate;
core->new_parent = new_parent;
@@ -1281,6 +1287,23 @@ static void clk_calc_subtree(struct clk_core *core, unsigned long new_rate,
if (new_parent && new_parent != core->parent)
new_parent->new_child = core;
+ if (core->ops->get_safe_parent) {
+ parent_hw = core->ops->get_safe_parent(core->hw, &safe_freq);
+ if (parent_hw) {
+ parent = parent_hw->core;
+ p_index = clk_fetch_parent_index(core, parent);
+ core->safe_parent_index = p_index;
+ core->safe_parent = parent;
+ if (safe_freq)
+ core->safe_freq = safe_freq;
+ else
+ core->safe_freq = 0;
+ }
+ } else {
+ core->safe_parent = NULL;
+ core->safe_freq = 0;
+ }
+
hlist_for_each_entry(child, &core->children, child_node) {
child->new_rate = clk_recalc(child, new_rate);
clk_calc_subtree(child, child->new_rate, NULL, 0);
@@ -1393,14 +1416,51 @@ static struct clk_core *clk_propagate_rate_change(struct clk_core *core,
unsigned long event)
{
struct clk_core *child, *tmp_clk, *fail_clk = NULL;
+ struct clk_core *old_parent;
int ret = NOTIFY_DONE;
- if (core->rate == core->new_rate)
+ if (core->rate == core->new_rate && event != POST_RATE_CHANGE)
return NULL;
+ switch (event) {
+ case PRE_RATE_CHANGE:
+ if (core->safe_parent) {
+ if (core->safe_freq)
+ core->ops->set_rate_and_parent(core->hw,
+ core->safe_freq,
+ core->safe_parent->rate,
+ core->safe_parent_index);
+ else
+ core->ops->set_parent(core->hw,
+ core->safe_parent_index);
+ }
+ core->old_rate = core->rate;
+ break;
+ case POST_RATE_CHANGE:
+ if (core->safe_parent) {
+ old_parent = __clk_set_parent_before(core,
+ core->new_parent);
+ if (core->ops->set_rate_and_parent) {
+ core->ops->set_rate_and_parent(core->hw,
+ core->new_rate,
+ core->new_parent ?
+ core->new_parent->rate : 0,
+ core->new_parent_index);
+ } else if (core->ops->set_parent) {
+ core->ops->set_parent(core->hw,
+ core->new_parent_index);
+ }
+ __clk_set_parent_after(core, core->new_parent,
+ old_parent);
+ }
+ break;
+ }
+
if (core->notifier_count) {
- ret = __clk_notify(core, event, core->rate, core->new_rate);
- if (ret & NOTIFY_STOP_MASK)
+ if (event != POST_RATE_CHANGE || core->old_rate != core->rate)
+ ret = __clk_notify(core, event, core->old_rate,
+ core->new_rate);
+ if (ret & NOTIFY_STOP_MASK && event != POST_RATE_CHANGE)
fail_clk = core;
}
@@ -1443,7 +1503,8 @@ static void clk_change_rate(struct clk_core *core)
else if (core->parent)
best_parent_rate = core->parent->rate;
- if (core->new_parent && core->new_parent != core->parent) {
+ if (core->new_parent && core->new_parent != core->parent &&
+ !core->safe_parent) {
old_parent = __clk_set_parent_before(core, core->new_parent);
trace_clk_set_parent(core, core->new_parent);
@@ -1527,6 +1588,8 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
core->req_rate = req_rate;
+ clk_propagate_rate_change(top, POST_RATE_CHANGE);
+
return ret;
}
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 0d3128fbc14e..173f681001f2 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -202,6 +202,8 @@ struct clk_ops {
struct clk_rate_request *req);
int (*set_parent)(struct clk_hw *hw, u8 index);
u8 (*get_parent)(struct clk_hw *hw);
+ struct clk_hw *(*get_safe_parent)(struct clk_hw *hw,
+ unsigned long *safe_freq);
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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