regmap: Ensure regmap_register_patch() is compatible with fast_io

With fast_io we use mutexes to lock the I/O operations so we would need
to do GFP_ATOMIC allocations if we wanted to do allocations inside the
lock as we do currently. Since it is unlikely that we will want to register
a patch outside of init where concurrency shouldn't be an issue move the
allocation of the patch data outside the lock.

Reported-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/base/regmap/regmap.c

@@ -2173,6 +2173,9 @@ EXPORT_SYMBOL_GPL(regmap_async_complete);
  * apply them immediately.  Typically this is used to apply
  * corrections to be applied to the device defaults on startup, such
  * as the updates some vendors provide to undocumented registers.
+ *
+ * The caller must ensure that this function cannot be called
+ * concurrently with either itself or regcache_sync().
  */
 int regmap_register_patch(struct regmap *map, const struct reg_default *regs,
 			  int num_regs)
@@ -2185,6 +2188,17 @@ int regmap_register_patch(struct regmap *map, const struct reg_default *regs,
 	    num_regs))
 		return 0;
 
+	p = krealloc(map->patch,
+		     sizeof(struct reg_default) * (map->patch_regs + num_regs),
+		     GFP_KERNEL);
+	if (p) {
+		memcpy(p + map->patch_regs, regs, num_regs * sizeof(*regs));
+		map->patch = p;
+		map->patch_regs += num_regs;
+	} else {
+		return -ENOMEM;
+	}
+
 	map->lock(map->lock_arg);
 
 	bypass = map->cache_bypass;
@@ -2202,17 +2216,6 @@ int regmap_register_patch(struct regmap *map, const struct reg_default *regs,
 		}
 	}
 
-	p = krealloc(map->patch,
-		     sizeof(struct reg_default) * (map->patch_regs + num_regs),
-		     GFP_KERNEL);
-	if (p) {
-		memcpy(p + map->patch_regs, regs, num_regs * sizeof(*regs));
-		map->patch = p;
-		map->patch_regs += num_regs;
-	} else {
-		ret = -ENOMEM;
-	}
-
 out:
 	map->async = false;
 	map->cache_bypass = bypass;