[PATCH v2 10/10] ASoC: tegra: Fix kcontrol put callback in Mixer

[Sameer Pujar <spujar@nvidia.com>]

The kcontrol put callback is expected to return 1 when there is change
in HW or when the update is acknowledged by driver. This would ensure
that change notifications are sent to subscribed applications. Filter
out duplicate updates in Mixer driver.

Fixes: 05bb3d5ec64a ("ASoC: tegra: Add Tegra210 based Mixer driver")
Signed-off-by: Sameer Pujar <spujar@nvidia.com>
Suggested-by: Jaroslav Kysela <perex@perex.cz>
Suggested-by: Mark Brown <broonie@kernel.org>
---
 sound/soc/tegra/tegra210_mixer.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/soc/tegra/tegra210_mixer.c b/sound/soc/tegra/tegra210_mixer.c
index 55e6177..d2d1946 100644
--- a/sound/soc/tegra/tegra210_mixer.c
+++ b/sound/soc/tegra/tegra210_mixer.c
@@ -210,6 +210,9 @@ static int tegra210_mixer_put_gain(struct snd_kcontrol *kcontrol,
 	id = (reg - TEGRA210_MIXER_GAIN_CFG_RAM_ADDR_0) /
 	     TEGRA210_MIXER_GAIN_CFG_RAM_ADDR_STRIDE;
 
+	if (mixer->gain_value[id] == ucontrol->value.integer.value[0])
+		return 0;
+
 	mixer->gain_value[id] = ucontrol->value.integer.value[0];
 
 	err = tegra210_mixer_configure_gain(cmpnt, id, instant_gain);
-- 
2.7.4