regmap: Allocate buffers with GFP_ATOMIC when fast_io == true

If a regmap is using fast_io, allocate the scratch buffer in
regmap_bulk_write() with GFP_ATOMIC instead of GFP_KERNEL.
Otherwise we may schedule while atomic.

Reported-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/internal.h

@@ -59,6 +59,7 @@ struct regmap {
 	regmap_lock lock;
 	regmap_unlock unlock;
 	void *lock_arg; /* This is passed to lock/unlock functions */
+	gfp_t alloc_flags;
 
 	struct device *dev; /* Device we do I/O on */
 	void *work_buf;     /* Scratch buffer used to format I/O */

drivers/base/regmap/regmap.c

@@ -561,6 +561,16 @@ struct regmap *__regmap_init(struct device *dev,
 		}
 		map->lock_arg = map;
 	}
+
+	/*
+	 * When we write in fast-paths with regmap_bulk_write() don't allocate
+	 * scratch buffers with sleeping allocations.
+	 */
+	if ((bus && bus->fast_io) || config->fast_io)
+		map->alloc_flags = GFP_ATOMIC;
+	else
+		map->alloc_flags = GFP_KERNEL;
+
 	map->format.reg_bytes = DIV_ROUND_UP(config->reg_bits, 8);
 	map->format.pad_bytes = config->pad_bits / 8;
 	map->format.val_bytes = DIV_ROUND_UP(config->val_bits, 8);
@@ -1786,7 +1796,7 @@ out:
 		if (!val_count)
 			return -EINVAL;
 
-		wval = kmemdup(val, val_count * val_bytes, GFP_KERNEL);
+		wval = kmemdup(val, val_count * val_bytes, map->alloc_flags);
 		if (!wval) {
 			dev_err(map->dev, "Error in memory allocation\n");
 			return -ENOMEM;