ASoC: arizona: Implement stability check for LHPF coefficients

Specifying unstable coefficients for the low/high pass filters can have
a severe impact on the audio. This patchs adds a stability check on the
coefficients written to the low/high pass filter block to prevent this.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/sound/soc/codecs/arizona.c b/sound/soc/codecs/arizona.c
index 39967863d2ec..a88202d768f4 100644
--- a/sound/soc/codecs/arizona.c
+++ b/sound/soc/codecs/arizona.c
@@ -2372,6 +2372,23 @@ out:
 }
 EXPORT_SYMBOL_GPL(arizona_eq_coeff_put);
 
+int arizona_lhpf_coeff_put(struct snd_kcontrol *kcontrol,
+			   struct snd_ctl_elem_value *ucontrol)
+{
+	struct snd_soc_codec *codec = snd_soc_kcontrol_codec(kcontrol);
+	struct arizona *arizona = dev_get_drvdata(codec->dev->parent);
+	__be16 *data = (__be16 *)ucontrol->value.bytes.data;
+	s16 val = be16_to_cpu(*data);
+
+	if (abs(val) >= 4096) {
+		dev_err(arizona->dev, "Rejecting unstable LHPF coefficients\n");
+		return -EINVAL;
+	}
+
+	return snd_soc_bytes_put(kcontrol, ucontrol);
+}
+EXPORT_SYMBOL_GPL(arizona_lhpf_coeff_put);
+
 MODULE_DESCRIPTION("ASoC Wolfson Arizona class device support");
 MODULE_AUTHOR("Mark Brown <broonie@opensource.wolfsonmicro.com>");
 MODULE_LICENSE("GPL");