diff options
author | Mike Tipton <quic_mdtipton@quicinc.com> | 2021-11-08 20:34:38 -0800 |
---|---|---|
committer | Stephen Boyd <sboyd@kernel.org> | 2021-12-07 19:20:35 -0800 |
commit | 54baf56eaa40aa5cdcd02b3c20d593e4e1211220 (patch) | |
tree | b77967d33946c158515e9a99028696a20d5935c1 | |
parent | 2d4fcc5ab35fac2e995f497d62439dcbb416babc (diff) |
clk: Don't parent clks until the parent is fully registered
Before commit fc0c209c147f ("clk: Allow parents to be specified without
string names") child clks couldn't find their parent until the parent
clk was added to a list in __clk_core_init(). After that commit, child
clks can reference their parent clks directly via a clk_hw pointer, or
they can lookup that clk_hw pointer via DT if the parent clk is
registered with an OF clk provider.
The common clk framework treats hw->core being non-NULL as "the clk is
registered" per the logic within clk_core_fill_parent_index():
parent = entry->hw->core;
/*
* We have a direct reference but it isn't registered yet?
* Orphan it and let clk_reparent() update the orphan status
* when the parent is registered.
*/
if (!parent)
Therefore we need to be extra careful to not set hw->core until the clk
is fully registered with the clk framework. Otherwise we can get into a
situation where a child finds a parent clk and we move the child clk off
the orphan list when the parent isn't actually registered, wrecking our
enable accounting and breaking critical clks.
Consider the following scenario:
CPU0 CPU1
---- ----
struct clk_hw clkBad;
struct clk_hw clkA;
clkA.init.parent_hws = { &clkBad };
clk_hw_register(&clkA) clk_hw_register(&clkBad)
... __clk_register()
hw->core = core
...
__clk_register()
__clk_core_init()
clk_prepare_lock()
__clk_init_parent()
clk_core_get_parent_by_index()
clk_core_fill_parent_index()
if (entry->hw) {
parent = entry->hw->core;
At this point, 'parent' points to clkBad even though clkBad hasn't been
fully registered yet. Ouch! A similar problem can happen if a clk
controller registers orphan clks that are referenced in the DT node of
another clk controller.
Let's fix all this by only setting the hw->core pointer underneath the
clk prepare lock in __clk_core_init(). This way we know that
clk_core_fill_parent_index() can't see hw->core be non-NULL until the
clk is fully registered.
Fixes: fc0c209c147f ("clk: Allow parents to be specified without string names")
Signed-off-by: Mike Tipton <quic_mdtipton@quicinc.com>
Link: https://lore.kernel.org/r/20211109043438.4639-1-quic_mdtipton@quicinc.com
[sboyd@kernel.org: Reword commit text, update comment]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
-rw-r--r-- | drivers/clk/clk.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index f467d63bbf1e..566ee2c78709 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -3418,6 +3418,14 @@ static int __clk_core_init(struct clk_core *core) clk_prepare_lock(); + /* + * Set hw->core after grabbing the prepare_lock to synchronize with + * callers of clk_core_fill_parent_index() where we treat hw->core + * being NULL as the clk not being registered yet. This is crucial so + * that clks aren't parented until their parent is fully registered. + */ + core->hw->core = core; + ret = clk_pm_runtime_get(core); if (ret) goto unlock; @@ -3582,8 +3590,10 @@ static int __clk_core_init(struct clk_core *core) out: clk_pm_runtime_put(core); unlock: - if (ret) + if (ret) { hlist_del_init(&core->child_node); + core->hw->core = NULL; + } clk_prepare_unlock(); @@ -3847,7 +3857,6 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw) core->num_parents = init->num_parents; core->min_rate = 0; core->max_rate = ULONG_MAX; - hw->core = core; ret = clk_core_populate_parent_map(core, init); if (ret) @@ -3865,7 +3874,7 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw) goto fail_create_clk; } - clk_core_link_consumer(hw->core, hw->clk); + clk_core_link_consumer(core, hw->clk); ret = __clk_core_init(core); if (!ret) |