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Documentation: clk: enable lock is not held for clk_is_enabled API

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

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Suggested-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Dong Aisheng <aisheng.dong@nxp.com>
[sboyd: Clarified the last sentence a little more and fixed a spelling
error]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
This commit is contained in:
Dong Aisheng 2018-01-19 21:37:15 +08:00 committed by Stephen Boyd
parent 7928b2cbe5
commit 5bc5673c09
1 changed files with 13 additions and 3 deletions
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16
Documentation/clk.txt
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@ -268,9 +268,19 @@ 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 the user of this API
needs to handle synchronizing the read of the state with whatever they're
using it for to make sure that the enable state doesn't change during that
time.
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