linux-kernel - [PATCH] regmap: Make regmap-mmio usable from atomic contexts

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Date:	Fri, 24 May 2013 10:29:22 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Mark Brown <broonie@...nel.org>,
	Stephen Warren <swarren@...dotorg.org>
Cc:	linux-kernel@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>
Subject: [PATCH] regmap: Make regmap-mmio usable from atomic contexts

regmap-mmio uses a spinlock with spin_lock() and spin_unlock() for locking.
To be able to use the regmap API from different contexts (atomic vs non-atomic),
without the risk of race conditions, we need to use spin_lock_irqsave() and
spin_lock_irqrestore() instead. A new field, the spinlock_flags field, is added
to regmap struct to store the flags between regmap_{,un}lock_spinlock(). The
spinlock_flags field itself is also protected by the spinlock.

Thanks to Stephen Warren for the suggestion of this particular solution.

Signed-off-by: Lars-Peter Clausen <lars@...afoo.de>
---
 drivers/base/regmap/internal.h | 1 +
 drivers/base/regmap/regmap.c   | 7 +++++--
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index b33a4ff..ae23d83 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -52,6 +52,7 @@ struct regmap_async {
 struct regmap {
 	struct mutex mutex;
 	spinlock_t spinlock;
+	unsigned long spinlock_flags;
 	regmap_lock lock;
 	regmap_unlock unlock;
 	void *lock_arg; /* This is passed to lock/unlock functions */
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 307f5a1..1a01553 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -302,13 +302,16 @@ static void regmap_unlock_mutex(void *__map)
 static void regmap_lock_spinlock(void *__map)
 {
 	struct regmap *map = __map;
-	spin_lock(&map->spinlock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&map->spinlock, flags);
+	map->spinlock_flags = flags;
 }
 
 static void regmap_unlock_spinlock(void *__map)
 {
 	struct regmap *map = __map;
-	spin_unlock(&map->spinlock);
+	spin_unlock_irqrestore(&map->spinlock, map->spinlock_flags);
 }
 
 static void dev_get_regmap_release(struct device *dev, void *res)
-- 
1.8.0

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