[1/1] Documentation: clk: enable lock is not held for clk_is_enabled API

Commit Message

Aisheng Dong Jan. 19, 2018, 1:37 p.m. UTC

The core does not need to hold enable lock for clk_is_enabled API.
Update the doc to reflect it.

Cc: Jonathan Corbet <[e-mail]>
Cc: Stephen Boyd <[e-mail]>
Suggested-by: Stephen Boyd <[e-mail]>
Signed-off-by: Dong Aisheng <[e-mail]>
---
 Documentation/clk.txt | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

Comments

Stephen Boyd March 16, 2018, 10:44 p.m. UTC | #1

Quoting Dong Aisheng (2018-01-19 05:37:15)
> The core does not need to hold enable lock for clk_is_enabled API.
> Update the doc to reflect it.
> 
> Cc: Jonathan Corbet <[e-mail]>
> Cc: Stephen Boyd <[e-mail]>
> Suggested-by: Stephen Boyd <[e-mail]>
> Signed-off-by: Dong Aisheng <[e-mail]>
> ---

Applied to clk-next

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Patch

diff --git a/Documentation/clk.txt b/Documentation/clk.txt
index be909ed..f286ff5 100644
--- a/Documentation/clk.txt
+++ b/Documentation/clk.txt
@@ -268,9 +268,17 @@  The common clock framework uses two global locks, the prepare lock and the
 enable lock.
 
 The enable lock is a spinlock and is held across calls to the .enable,
-.disable and .is_enabled operations. Those operations are thus not allowed to
-sleep, and calls to the clk_enable(), clk_disable() and clk_is_enabled() API
-functions are allowed in atomic context.
+.disable operations. Those operations are thus not allowed to sleep,
+and calls to the clk_enable(), clk_disable() API functions are allowed in
+atomic context.
+
+For clk_is_enabled() API, it is also designed to be allowed to be used in
+atomic context. However, it doesn't really make any sense to hold the enable
+lock in core, unless you want to do something else with the information of
+the enable state with that lock held. Otherwise, seeing if a clk is enabled is
+a one-shot read of the enabled state, which could just as easily change after
+the function returns because the lock is released. Thus driver onwer needs
+judge and take care of it in their driver if it needs lock.
 
 The prepare lock is a mutex and is held across calls to all other operations.
 All those operations are allowed to sleep, and calls to the corresponding API