regmap: cache: Do not fail silently from regcache_sync calls

Call stack of regcache_sync calls may not emit any error message even if
operation was cancelled due an error in I/O driver. One such a silent error
is for instance if I2C bus driver doesn't receive ACK from the I2C device
and returns -EREMOTEIO.

Since many users of regcache_sync() don't check and print the error there is
no any indication that HW registers are potentially out of sync.
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/regcache.c

@@ -269,8 +269,11 @@ static int regcache_default_sync(struct regmap *map, unsigned int min,
 		map->cache_bypass = 1;
 		ret = _regmap_write(map, reg, val);
 		map->cache_bypass = 0;
-		if (ret)
+		if (ret) {
+			dev_err(map->dev, "Unable to sync register %#x. %d\n",
+				reg, ret);
 			return ret;
+		}
 		dev_dbg(map->dev, "Synced register %#x, value %#x\n", reg, val);
 	}
 
@@ -615,8 +618,11 @@ static int regcache_sync_block_single(struct regmap *map, void *block,
 		ret = _regmap_write(map, regtmp, val);
 
 		map->cache_bypass = 0;
-		if (ret != 0)
+		if (ret != 0) {
+			dev_err(map->dev, "Unable to sync register %#x. %d\n",
+				regtmp, ret);
 			return ret;
+		}
 		dev_dbg(map->dev, "Synced register %#x, value %#x\n",
 			regtmp, val);
 	}
@@ -641,6 +647,9 @@ static int regcache_sync_block_raw_flush(struct regmap *map, const void **data,
 	map->cache_bypass = 1;
 
 	ret = _regmap_raw_write(map, base, *data, count * val_bytes);
+	if (ret)
+		dev_err(map->dev, "Unable to sync registers %#x-%#x. %d\n",
+			base, cur - map->reg_stride, ret);
 
 	map->cache_bypass = 0;