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clk: Port clock dependency resolution code 

Port the clock dependency resolution algorithm utilized by Linux
kernel's version of of_clk_init(), to allow for SoCs whose DT clock
configuration reqires such behaviour for correct initialization (Vybrid
is one such example).

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
This commit is contained in:
Andrey Smirnov 2016-11-09 08:13:56 -08:00 committed by Sascha Hauer
parent 49877e3125
commit 764f84809f
1 changed files with 82 additions and 7 deletions
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89
drivers/clk/clk.c
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@ -404,7 +404,7 @@ EXPORT_SYMBOL_GPL(of_clk_del_provider);
struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec)
{
struct of_clk_provider *provider;
struct clk *clk = ERR_PTR(-ENOENT);
struct clk *clk = ERR_PTR(-EPROBE_DEFER);
/* Check if we have such a provider in our array */
list_for_each_entry(provider, &of_clk_providers, link) {
@ -437,6 +437,47 @@ char *of_clk_get_parent_name(struct device_node *np, unsigned int index)
}
EXPORT_SYMBOL_GPL(of_clk_get_parent_name);
struct clock_provider {
of_clk_init_cb_t clk_init_cb;
struct device_node *np;
struct list_head node;
};
/*
* This function looks for a parent clock. If there is one, then it
* checks that the provider for this parent clock was initialized, in
* this case the parent clock will be ready.
*/
static int parent_ready(struct device_node *np)
{
int i = 0;
while (true) {
struct clk *clk = of_clk_get(np, i);
/* this parent is ready we can check the next one */
if (!IS_ERR(clk)) {
clk_put(clk);
i++;
continue;
}
/* at least one parent is not ready, we exit now */
if (PTR_ERR(clk) == -EPROBE_DEFER)
return 0;
/*
* Here we make assumption that the device tree is
* written correctly. So an error means that there is
* no more parent. As we didn't exit yet, then the
* previous parent are ready. If there is no clock
* parent, no need to wait for them, then we can
* consider their absence as being ready
*/
return 1;
}
}
/**
* of_clk_init() - Scan and init clock providers from the DT
* @root: parent of the first level to probe or NULL for the root of the tree
@ -449,8 +490,11 @@ EXPORT_SYMBOL_GPL(of_clk_get_parent_name);
*/
int of_clk_init(struct device_node *root, const struct of_device_id *matches)
{
struct clock_provider *clk_provider, *next;
bool is_init_done;
bool force = false;
LIST_HEAD(clk_provider_list);
const struct of_device_id *match;
int rc;
if (!root)
root = of_find_node_by_path("/");
@ -459,12 +503,43 @@ int of_clk_init(struct device_node *root, const struct of_device_id *matches)
if (!matches)
matches = __clk_of_table_start;
/* First prepare the list of the clocks providers */
for_each_matching_node_and_match(root, matches, &match) {
of_clk_init_cb_t clk_init_cb = (of_clk_init_cb_t)match->data;
rc = clk_init_cb(root);
if (rc)
pr_err("%s: failed to init clock for %s: %d\n",
__func__, root->full_name, rc);
struct clock_provider *parent;
if (!of_device_is_available(root))
continue;
parent = xzalloc(sizeof(*parent));
parent->clk_init_cb = match->data;
parent->np = root;
list_add_tail(&parent->node, &clk_provider_list);
}
while (!list_empty(&clk_provider_list)) {
is_init_done = false;
list_for_each_entry_safe(clk_provider, next,
&clk_provider_list, node) {
if (force || parent_ready(clk_provider->np)) {
clk_provider->clk_init_cb(clk_provider->np);
list_del(&clk_provider->node);
free(clk_provider);
is_init_done = true;
}
}
/*
* We didn't manage to initialize any of the
* remaining providers during the last loop, so now we
* initialize all the remaining ones unconditionally
* in case the clock parent was not mandatory
*/
if (!is_init_done)
force = true;
}
return 0;