regmap: Use different lockdep class for each regmap init call

Lockdep validator complains about recursive locking and deadlock
when two different regmap instances are called in a nested order.
That happens anytime a regmap read/write call needs to access
another regmap.

This is because, for performance reason, lockdep groups all locks
initialized by the same mutex_init() in the same lock class.
Therefore all regmap mutexes are in the same lock class, leading
to lockdep "nested locking" warnings if a regmap accesses another
regmap.

In general, it is impossible to establish in advance the hierarchy
of regmaps, so we make sure that each regmap init call initializes
its own static lock_class_key. This is done by wrapping all
regmap_init calls into macros.

This also allows us to give meaningful names to the lock_class_key.
For example, in rt5677 case, we have in /proc/lockdep_chains:
irq_context: 0
[ffffffc0018d2198] &dev->mutex
[ffffffc0018d2198] &dev->mutex
[ffffffc001bd7f60] rt5677:5104:(&rt5677_regmap)->_lock
[ffffffc001bd7f58] rt5677:5096:(&rt5677_regmap_physical)->_lock
[ffffffc001b95448] &(&base->lock)->rlock

The above would have resulted in a lockdep recursive warning
previously. This is not the case anymore as the lockdep validator
now clearly identifies the 2 regmaps as separate.

Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 17 insertions, 10 deletions

diff --git a/drivers/base/regmap/regmap-mmio.c b/drivers/base/regmap/regmap-mmio.c
index 04a329a377e9..a1b2b270e4bc 100644
--- a/drivers/base/regmap/regmap-mmio.c
+++ b/drivers/base/regmap/regmap-mmio.c
@@ -307,9 +307,11 @@ err_free:
  * The return value will be an ERR_PTR() on error or a valid pointer to
  * a struct regmap.
  */
-struct regmap *regmap_init_mmio_clk(struct device *dev, const char *clk_id,
-				    void __iomem *regs,
-				    const struct regmap_config *config)
+struct regmap *__regmap_init_mmio_clk(struct device *dev, const char *clk_id,
+				      void __iomem *regs,
+				      const struct regmap_config *config,
+				      struct lock_class_key *lock_key,
+				      const char *lock_name)
 {
 	struct regmap_mmio_context *ctx;
 
@@ -317,9 +319,10 @@ struct regmap *regmap_init_mmio_clk(struct device *dev, const char *clk_id,
 	if (IS_ERR(ctx))
 		return ERR_CAST(ctx);
 
-	return regmap_init(dev, &regmap_mmio, ctx, config);
+	return __regmap_init(dev, &regmap_mmio, ctx, config,
+			     lock_key, lock_name);
 }
-EXPORT_SYMBOL_GPL(regmap_init_mmio_clk);
+EXPORT_SYMBOL_GPL(__regmap_init_mmio_clk);
 
 /**
  * devm_regmap_init_mmio_clk(): Initialise managed register map with clock
@@ -333,9 +336,12 @@ EXPORT_SYMBOL_GPL(regmap_init_mmio_clk);
  * to a struct regmap.  The regmap will be automatically freed by the
  * device management code.
  */
-struct regmap *devm_regmap_init_mmio_clk(struct device *dev, const char *clk_id,
-					 void __iomem *regs,
-					 const struct regmap_config *config)
+struct regmap *__devm_regmap_init_mmio_clk(struct device *dev,
+					   const char *clk_id,
+					   void __iomem *regs,
+					   const struct regmap_config *config,
+					   struct lock_class_key *lock_key,
+					   const char *lock_name)
 {
 	struct regmap_mmio_context *ctx;
 
@@ -343,8 +349,9 @@ struct regmap *devm_regmap_init_mmio_clk(struct device *dev, const char *clk_id,
 	if (IS_ERR(ctx))
 		return ERR_CAST(ctx);
 
-	return devm_regmap_init(dev, &regmap_mmio, ctx, config);
+	return __devm_regmap_init(dev, &regmap_mmio, ctx, config,
+				  lock_key, lock_name);
 }
-EXPORT_SYMBOL_GPL(devm_regmap_init_mmio_clk);
+EXPORT_SYMBOL_GPL(__devm_regmap_init_mmio_clk);
 
 MODULE_LICENSE("GPL v2");