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authorUlf Hansson <ulf.hansson@linaro.org>2013-04-02 23:09:39 +0200
committerMike Turquette <mturquette@linaro.org>2013-04-08 18:19:40 -0700
commita68de8e4ab2756d8e125cf327f044c895b6a6b3d (patch)
tree889c89b211daef76880c3563f20b2423fca771c7 /drivers/clk
parent031dcc9bd4164a7482b89987d5b9ecb3af5e9033 (diff)
downloadop-kernel-dev-a68de8e4ab2756d8e125cf327f044c895b6a6b3d.zip
op-kernel-dev-a68de8e4ab2756d8e125cf327f044c895b6a6b3d.tar.gz
clk: Fixup locking issues for clk_set_parent
Updating the clock tree topology must be protected with the spinlock when doing clk_set_parent, otherwise we can not handle the migration of the enable_count in a safe manner. While issuing the .set_parent callback to make the clk-hw perform the switch to the new parent, we can not hold the spinlock since it is must be allowed to be slow path. This complicates error handling, but is still possible to achieve. Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> Cc: Rajagopal Venkat <rajagopal.venkat@linaro.org> Signed-off-by: Mike Turquette <mturquette@linaro.org>
Diffstat (limited to 'drivers/clk')
-rw-r--r--drivers/clk/clk.c67
1 files changed, 52 insertions, 15 deletions
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index c83e8e5..de6b459 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1363,31 +1363,71 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent, u8 p_index)
unsigned long flags;
int ret = 0;
struct clk *old_parent = clk->parent;
+ bool migrated_enable = false;
- /* migrate prepare and enable */
+ /* migrate prepare */
if (clk->prepare_count)
__clk_prepare(parent);
- /* FIXME replace with clk_is_enabled(clk) someday */
flags = clk_enable_lock();
- if (clk->enable_count)
+
+ /* migrate enable */
+ if (clk->enable_count) {
__clk_enable(parent);
+ migrated_enable = true;
+ }
+
+ /* update the clk tree topology */
+ clk_reparent(clk, parent);
+
clk_enable_unlock(flags);
/* change clock input source */
if (parent && clk->ops->set_parent)
ret = clk->ops->set_parent(clk->hw, p_index);
- /* clean up old prepare and enable */
- flags = clk_enable_lock();
- if (clk->enable_count)
+ if (ret) {
+ /*
+ * The error handling is tricky due to that we need to release
+ * the spinlock while issuing the .set_parent callback. This
+ * means the new parent might have been enabled/disabled in
+ * between, which must be considered when doing rollback.
+ */
+ flags = clk_enable_lock();
+
+ clk_reparent(clk, old_parent);
+
+ if (migrated_enable && clk->enable_count) {
+ __clk_disable(parent);
+ } else if (migrated_enable && (clk->enable_count == 0)) {
+ __clk_disable(old_parent);
+ } else if (!migrated_enable && clk->enable_count) {
+ __clk_disable(parent);
+ __clk_enable(old_parent);
+ }
+
+ clk_enable_unlock(flags);
+
+ if (clk->prepare_count)
+ __clk_unprepare(parent);
+
+ return ret;
+ }
+
+ /* clean up enable for old parent if migration was done */
+ if (migrated_enable) {
+ flags = clk_enable_lock();
__clk_disable(old_parent);
- clk_enable_unlock(flags);
+ clk_enable_unlock(flags);
+ }
+ /* clean up prepare for old parent if migration was done */
if (clk->prepare_count)
__clk_unprepare(old_parent);
- return ret;
+ /* update debugfs with new clk tree topology */
+ clk_debug_reparent(clk, parent);
+ return 0;
}
/**
@@ -1450,14 +1490,11 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
/* do the re-parent */
ret = __clk_set_parent(clk, parent, p_index);
- /* propagate ABORT_RATE_CHANGE if .set_parent failed */
- if (ret) {
+ /* propagate rate recalculation accordingly */
+ if (ret)
__clk_recalc_rates(clk, ABORT_RATE_CHANGE);
- goto out;
- }
-
- /* propagate rate recalculation downstream */
- __clk_reparent(clk, parent);
+ else
+ __clk_recalc_rates(clk, POST_RATE_CHANGE);
out:
clk_prepare_unlock();
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