This adds a new clk_op, pre_rate_req. It allows clks to setup an
intermediate state when clk rates are changed. One use case for this
is when a clk needs to switch to a safe parent when its PLL ancestor
changes rates. This is needed when a PLL cannot guarantee that it will
not exceed the new rate before it locks. The set_rate, set_parent, and
set_rate_and_parent callbacks are used with the pre_rate_req callback.
Signed-off-by: Derek Basehore <dbasehore@xxxxxxxxxxxx>
---
drivers/clk/clk.c | 136 +++++++++++++++++++++++++++++++++--
include/linux/clk-provider.h | 10 +++
2 files changed, 139 insertions(+), 7 deletions(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 1db44b4e46b0..36a2f929ab8d 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -39,6 +39,7 @@ static int enable_refcnt;
static HLIST_HEAD(clk_root_list);
static HLIST_HEAD(clk_orphan_list);
static LIST_HEAD(clk_notifier_list);
+static LIST_HEAD(pre_change_free_list);
/*** private data structures ***/
@@ -1896,6 +1897,74 @@ static struct clk_core *clk_propagate_rate_change(struct clk_core *core,
return fail_clk;
}
+static int clk_pre_rate_req(struct list_head *pre_list, struct clk_core *core)
+{
+ struct clk_core *child, *parent = core->parent;
+ struct clk_rate_request next, pre;
+ struct clk_change *change;
+ int ret;
+
+ hlist_for_each_entry(child, &core->children, child_node) {
+ ret = clk_pre_rate_req(pre_list, child);
+ if (ret)
+ return ret;
+ }
+
+ if (core->new_child) {
+ ret = clk_pre_rate_req(pre_list, child);
+ if (ret)
+ return ret;
+ }
+
+ if (!core->ops->pre_rate_req)
+ return 0;
+
+ if (core->change.parent)
+ parent = core->change.parent;
+
+ if (parent) {
+ next.best_parent_hw = parent->hw;
+ next.best_parent_rate = parent->change.rate;
+ }
+
+ next.rate = core->change.rate;
+ clk_core_get_boundaries(core, &next.min_rate, &next.max_rate);
+
+ ret = core->ops->pre_rate_req(core->hw, &next, &pre);
+ if (ret < 0)
+ return ret;
+ else if (!ret)
+ goto out;
+
+ /*
+ * We allocate a change for each clk with the pre_rate_req op. If we run
+ * out, that's because we wrapped around to a clk again in the
+ * pre_rate_req step which is not allowed.
+ */
+ change = list_first_entry(&pre_change_free_list, struct clk_change,
+ change_list);
+ if (IS_ERR_OR_NULL(change)) {
+ pr_err("%s: pre_rate_req loop detected on clk %s. All pre_rate_req clk_change structs are used\n",
+ __func__, core->name);
+ return -EDEADLK;
+ }
+
+ change->core = core;
+ change->rate = pre.rate;
+ change->parent = pre.best_parent_hw ? pre.best_parent_hw->core : NULL;
+ list_move(&change->change_list, pre_list);
+
+out:
+ /* If the pre req req pulls in a new parent, add it to the call chain */
+ if (parent != change->parent) {
+ ret = clk_pre_rate_req(pre_list, change->parent);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
/*
* walk down a subtree and set the new rates notifying the rate
* change on the way
@@ -2065,6 +2134,8 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
struct clk_core *top, *fail_clk;
struct clk_change *change, *tmp;
unsigned long rate;
+ LIST_HEAD(pre_changes);
+ LIST_HEAD(post_changes);
LIST_HEAD(changes);
int ret = 0;
@@ -2092,6 +2163,14 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
clk_calc_subtree(core);
+ /* We need a separate list for these changes due to error handling. */
+ ret = clk_pre_rate_req(&pre_changes, top);
+ if (ret) {
+ pr_debug("%s: failed pre_rate_req via top clk %s: %d\n",
+ __func__, top->name, ret);
+ goto pre_rate_req;
+ }
+
/* Construct the list of changes */
clk_prepare_changes(&changes, top);
@@ -2100,11 +2179,19 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
if (fail_clk) {
pr_debug("%s: failed to set %s rate\n", __func__,
fail_clk->name);
- clk_propagate_rate_change(top, ABORT_RATE_CHANGE);
ret = -EBUSY;
- goto err;
+ goto prop_rate;
+ }
+
+ ret = clk_change_rates(&pre_changes);
+ if (ret) {
+ pr_debug("%s: rate rate changes failed via top clk %s: %d\n",
+ __func__, top->name, ret);
+ goto pre_rate_req;
}
+ list_splice_tail(&post_changes, &changes);
+
/* change the rates */
ret = clk_change_rates(&changes);
list_for_each_entry_safe(change, tmp, &changes, change_list) {
@@ -2112,16 +2199,28 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
change->parent = NULL;
list_del_init(&change->change_list);
}
-
if (ret) {
pr_debug("%s: failed to set %s rate via top clk %s\n", __func__,
core->name, top->name);
- clk_propagate_rate_change(top, ABORT_RATE_CHANGE);
- goto err;
+ goto change_rates;
}
+ list_splice(&pre_changes, &pre_change_free_list);
core->req_rate = req_rate;
-err:
+
+ return 0;
+
+change_rates:
+ WARN_ON(clk_change_rates(&pre_changes));
+pre_rate_req:
+ list_splice(&pre_changes, &pre_change_free_list);
+prop_rate:
+ clk_propagate_rate_change(top, ABORT_RATE_CHANGE);
+ list_for_each_entry_safe(change, tmp, &changes, change_list) {
+ change->rate = 0;
+ change->parent = NULL;
+ list_del_init(&change->change_list);
+ }
clk_pm_runtime_put(core);
return ret;
@@ -3139,7 +3238,9 @@ static int __clk_core_init(struct clk_core *core)
/* check that clk_ops are sane. See Documentation/driver-api/clk.rst */
if (core->ops->set_rate &&
- !((core->ops->round_rate || core->ops->determine_rate) &&
+ !((core->ops->round_rate ||
+ core->ops->determine_rate ||
+ core->ops->pre_rate_req) &&
core->ops->recalc_rate)) {
pr_err("%s: %s must implement .round_rate or .determine_rate in addition to .recalc_rate\n",
__func__, core->name);
@@ -3175,6 +3276,20 @@ static int __clk_core_init(struct clk_core *core)
"%s: invalid NULL in %s's .parent_names\n",
__func__, core->name);
+ /* Allocate a clk_change struct for pre_rate_reqs */
+ if (core->ops->pre_rate_req) {
+ struct clk_change *change = kzalloc(sizeof(*change),
+ GFP_KERNEL);
+ if (!change) {
+ ret = -ENOMEM;
+ kfree(core->parents);
+ goto out;
+ }
+
+ INIT_LIST_HEAD(&change->change_list);
+ list_add(&pre_change_free_list, &change->change_list);
+ }
+
core->parent = __clk_init_parent(core);
/*
@@ -3476,6 +3591,13 @@ static void __clk_release(struct kref *ref)
while (--i >= 0)
kfree_const(core->parent_names[i]);
+ if (core->ops->pre_rate_req) {
+ struct clk_change *change =
+ list_first_entry(&pre_change_free_list,
+ struct clk_change, change_list);
+ list_del(&change->change_list);
+ kfree(change);
+ }
kfree(core->parent_names);
kfree_const(core->name);
kfree(core);
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 60c51871b04b..98a65c6c326d 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -138,6 +138,13 @@ struct clk_duty {
* actually supported by the clock, and optionally the parent clock
* that should be used to provide the clock rate.
*
+ * @pre_rate_req: Given the next state that the clk will enter via a
+ * clk_rate_request struct, next, fill in another clk_rate_request
+ * struct, pre, with any desired intermediate state to change to
+ * before the state in next is applied. Returns positive to request
+ * an intermediate state transition, 0 for no transition, and
+ * -EERROR otherwise.
+ *
* @set_parent: Change the input source of this clock; for clocks with multiple
* possible parents specify a new parent by passing in the index
* as a u8 corresponding to the parent in either the .parent_names
@@ -236,6 +243,9 @@ struct clk_ops {
unsigned long *parent_rate);
int (*determine_rate)(struct clk_hw *hw,
struct clk_rate_request *req);
+ int (*pre_rate_req)(struct clk_hw *hw,
+ const struct clk_rate_request *next,
+ struct clk_rate_request *pre);
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 rate,
--
2.19.1.568.g152ad8e336-goog
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