hwspinlock: add the 'in_atomic' API

Add the 'in_atomic' mode which can be called from an atomic context.
This mode relies on the existing 'raw' mode (no lock, no preemption/irq
disabling) with the difference that the timeout is not based on jiffies
(jiffies won't increase when irq are disabled) but handled with
busy-waiting udelay() calls.

Signed-off-by: Fabien Dessenne <fabien.dessenne@st.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

1 files changed, 39 insertions, 0 deletions

diff --git a/Documentation/hwspinlock.txt b/Documentation/hwspinlock.txt
index c3403f9ae27a..6f03713b7003 100644
--- a/Documentation/hwspinlock.txt
+++ b/Documentation/hwspinlock.txt
@@ -153,6 +153,22 @@ The function will never sleep.
 
 ::
 
+  int hwspin_lock_timeout_in_atomic(struct hwspinlock *hwlock, unsigned int to);
+
+Lock a previously-assigned hwspinlock with a timeout limit (specified in
+msecs). If the hwspinlock is already taken, the function will busy loop
+waiting for it to be released, but give up when the timeout elapses.
+
+This function shall be called only from an atomic context and the timeout
+value shall not exceed a few msecs.
+
+Returns 0 when successful and an appropriate error code otherwise (most
+notably -ETIMEDOUT if the hwspinlock is still busy after timeout msecs).
+
+The function will never sleep.
+
+::
+
   int hwspin_trylock(struct hwspinlock *hwlock);
 
 
@@ -218,6 +234,19 @@ The function will never sleep.
 
 ::
 
+  int hwspin_trylock_in_atomic(struct hwspinlock *hwlock);
+
+Attempt to lock a previously-assigned hwspinlock, but immediately fail if
+it is already taken.
+
+This function shall be called only from an atomic context.
+
+Returns 0 on success and an appropriate error code otherwise (most
+notably -EBUSY if the hwspinlock was already taken).
+The function will never sleep.
+
+::
+
   void hwspin_unlock(struct hwspinlock *hwlock);
 
 Unlock a previously-locked hwspinlock. Always succeed, and can be called
@@ -264,6 +293,16 @@ This function will never sleep.
 
 ::
 
+  void hwspin_unlock_in_atomic(struct hwspinlock *hwlock);
+
+Unlock a previously-locked hwspinlock.
+
+The caller should **never** unlock an hwspinlock which is already unlocked.
+Doing so is considered a bug (there is no protection against this).
+This function will never sleep.
+
+::
+
   int hwspin_lock_get_id(struct hwspinlock *hwlock);
 
 Retrieve id number of a given hwspinlock. This is needed when an