Patch "drm/fsl-dcu: use flat regmap cache" has been added to the 4.6-stable tree

This is a note to let you know that I've just added the patch titled

drm/fsl-dcu: use flat regmap cache

to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-fsl-dcu-use-flat-regmap-cache.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Stefan Agner <[email protected]>
Date: Fri, 3 Jun 2016 14:21:34 -0700
Subject: drm/fsl-dcu: use flat regmap cache

From: Stefan Agner <[email protected]>

commit ce492b3b8f99cf9d2f807ec22d8805c996a09503 upstream.

Using flat regmap cache instead of RB-tree to avoid the following lockdep warning on driver load:

WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:2755 lockdep_trace_alloc+0x15c/0x160()

DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))

The RB-tree regmap cache needs to allocate new space on first writes. However, allocations in an atomic context (e.g. when a spinlock is held) are not allowed. The function regmap_write calls map->lock, which acquires a spinlock in the fast_io case. Since the FSL DCU driver uses MMIO, the regmap bus of type regmap_mmio is being used which has fast_io set to true.

Use flat regmap cache and specify max register to be large enouth to cover all registers available in LS1021a and Vybrids register space.

---
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -40,9 +40,10 @@ static const struct regmap_config fsl_dc
 	.reg_bits = 32,
 	.reg_stride = 4,
 	.val_bits = 32,
-	.cache_type = REGCACHE_RBTREE,
+	.cache_type = REGCACHE_FLAT,
 
 	.volatile_reg = fsl_dcu_drm_is_volatile_reg,
+	.max_register = 0x11fc,
 };
 
 static int fsl_dcu_drm_irq_init(struct drm_device *dev)

Patches currently in stable-queue which might be from [email protected] are

queue-4.6/drm-fsl-dcu-use-flat-regmap-cache.patch