@@ -67,6 +67,8 @@ struct clk_core {
struct hlist_head children;
struct hlist_node child_node;
struct hlist_head clks;
+ struct list_head prepare_list;
+ struct list_head enable_list;
unsigned int notifier_count;
#ifdef CONFIG_DEBUG_FS
struct dentry *dentry;
@@ -523,33 +525,43 @@ EXPORT_SYMBOL_GPL(clk_unprepare);
static int clk_core_prepare(struct clk_core *core)
{
int ret = 0;
+ struct clk_core *tmp, *parent;
+ LIST_HEAD(head);
lockdep_assert_held(&prepare_lock);
- if (!core)
- return 0;
+ while (core) {
+ list_add(&core->prepare_list, &head);
+ /* Stop once we see a clk that is already prepared */
+ if (core->prepare_count)
+ break;
+ core = core->parent;
+ }
- if (core->prepare_count == 0) {
- ret = clk_core_prepare(core->parent);
- if (ret)
- return ret;
+ list_for_each_entry_safe(core, tmp, &head, prepare_list) {
+ list_del_init(&core->prepare_list);
- trace_clk_prepare(core);
+ if (core->prepare_count == 0) {
+ trace_clk_prepare(core);
- if (core->ops->prepare)
- ret = core->ops->prepare(core->hw);
+ if (core->ops->prepare)
+ ret = core->ops->prepare(core->hw);
- trace_clk_prepare_complete(core);
+ trace_clk_prepare_complete(core);
- if (ret) {
- clk_core_unprepare(core->parent);
- return ret;
+ if (ret)
+ goto err;
}
+ core->prepare_count++;
}
- core->prepare_count++;
-
return 0;
+err:
+ parent = core->parent;
+ list_for_each_entry_safe_continue(core, tmp, &head, prepare_list)
+ list_del_init(&core->prepare_list);
+ clk_core_unprepare(parent);
+ return ret;
}
static int clk_core_prepare_lock(struct clk_core *core)
@@ -643,36 +655,49 @@ EXPORT_SYMBOL_GPL(clk_disable);
static int clk_core_enable(struct clk_core *core)
{
int ret = 0;
+ struct clk_core *tmp, *parent, *prev;
+ LIST_HEAD(head);
lockdep_assert_held(&enable_lock);
- if (!core)
- return 0;
-
- if (WARN_ON(core->prepare_count == 0))
- return -ESHUTDOWN;
+ while (core) {
+ list_add(&core->enable_list, &head);
+ /* Stop once we see a clk that is already enabled */
+ if (core->enable_count)
+ break;
+ core = core->parent;
+ }
- if (core->enable_count == 0) {
- ret = clk_core_enable(core->parent);
+ list_for_each_entry_safe(core, tmp, &head, enable_list) {
+ list_del_init(&core->enable_list);
- if (ret)
- return ret;
+ if (WARN_ON(core->prepare_count == 0)) {
+ ret = -ESHUTDOWN;
+ goto err;
+ }
- trace_clk_enable_rcuidle(core);
+ if (core->enable_count == 0) {
+ trace_clk_enable_rcuidle(core);
- if (core->ops->enable)
- ret = core->ops->enable(core->hw);
+ if (core->ops->enable)
+ ret = core->ops->enable(core->hw);
- trace_clk_enable_complete_rcuidle(core);
+ trace_clk_enable_complete_rcuidle(core);
- if (ret) {
- clk_core_disable(core->parent);
- return ret;
+ if (ret)
+ goto err;
}
+
+ core->enable_count++;
}
- core->enable_count++;
return 0;
+err:
+ parent = core->parent;
+ list_for_each_entry_safe_continue(core, tmp, &head, enable_list)
+ list_del_init(&core->enable_list);
+ clk_core_disable(parent);
+ return ret;
}
static int clk_core_enable_lock(struct clk_core *core)
@@ -2590,6 +2615,8 @@ struct clk *clk_register(struct device *dev, struct clk_hw *hw)
core->num_parents = hw->init->num_parents;
core->min_rate = 0;
core->max_rate = ULONG_MAX;
+ INIT_LIST_HEAD(&core->prepare_list);
+ INIT_LIST_HEAD(&core->enable_list);
hw->core = core;
/* allocate local copy in case parent_names is __initdata */
Enabling and preparing clocks can be written quite naturally with recursion. We start at some point in the tree and recurse up the tree to find the oldest parent clk that needs to be enabled or prepared. Then we enable/prepare and return to the caller, going back to the clk we started at and enabling/preparing along the way. The problem is recursion isn't great for kernel code where we have a limited stack size. Furthermore, we may be calling this code inside clk_set_rate() which also has recursion in it, so we're really not looking good if we encounter a tall clk tree. Let's create a stack instead by looping over the parent chain and collecting clks of interest. Then the enable/prepare becomes as simple as iterating over that list and calling enable. Cc: Jerome Brunet <jbrunet@baylibre.com> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> --- I have some vague fear that this may not work if a clk op is framework reentrant and attemps to call consumer clk APIs from within the clk ops. If the reentrant call tries to add a clk that's already in the list then we'll corrupt the list. Ugh. drivers/clk/clk.c | 91 ++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 59 insertions(+), 32 deletions(-)