[ALSA] Fix CS4270 volume control and optimize I2C operations

[pandora-kernel.git] / sound / soc / codecs / cs4270.c

diff --git a/sound/soc/codecs/cs4270.c b/sound/soc/codecs/cs4270.c
index 43d50a4..5d601ad 100644 (file)
--- a/sound/soc/codecs/cs4270.c
+++ b/sound/soc/codecs/cs4270.c
@@ -294,19 +294,24 @@ static unsigned int cs4270_read_reg_cache(struct snd_soc_codec *codec,
 static int cs4270_i2c_write(struct snd_soc_codec *codec, unsigned int reg,
                            unsigned int value)
 {
+       u8 *cache = codec->reg_cache;
+
        if ((reg < CS4270_FIRSTREG) || (reg > CS4270_LASTREG))
                return -EIO;
 
-       if (i2c_smbus_write_byte_data(codec->control_data, reg, value) == 0) {
+       /* Only perform an I2C operation if the new value is different */
+       if (cache[reg - CS4270_FIRSTREG] != value) {
+               struct i2c_client *client = codec->control_data;
+               if (i2c_smbus_write_byte_data(client, reg, value)) {
+                       printk(KERN_ERR "cs4270: I2C write failed\n");
+                       return -EIO;
+               }
+
                /* We've written to the hardware, so update the cache */
-               u8 *cache = codec->reg_cache;
                cache[reg - CS4270_FIRSTREG] = value;
-               return 0;
-       } else {
-               printk(KERN_ERR "cs4270: I2C write of register %u failed\n",
-                       reg);
-               return -EIO;
        }
+
+       return 0;
 }
 
 /*
@@ -521,7 +526,7 @@ static int cs4270_i2c_detach(struct i2c_client *client)
 /* A list of non-DAPM controls that the CS4270 supports */
 static const struct snd_kcontrol_new cs4270_snd_controls[] = {
        SOC_DOUBLE_R("Master Playback Volume",
-               CS4270_VOLA, CS4270_VOLB, 0, 0xFF, 0)
+               CS4270_VOLA, CS4270_VOLB, 0, 0xFF, 1)
 };
 
 static struct i2c_driver cs4270_i2c_driver = {