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-rw-r--r--target/linux/brcm2708/patches-4.4/0143-Allow-up-to-24dB-digital-gain-to-be-applied-when-usi.patch99
1 files changed, 99 insertions, 0 deletions
diff --git a/target/linux/brcm2708/patches-4.4/0143-Allow-up-to-24dB-digital-gain-to-be-applied-when-usi.patch b/target/linux/brcm2708/patches-4.4/0143-Allow-up-to-24dB-digital-gain-to-be-applied-when-usi.patch
new file mode 100644
index 0000000000..258210bd42
--- /dev/null
+++ b/target/linux/brcm2708/patches-4.4/0143-Allow-up-to-24dB-digital-gain-to-be-applied-when-usi.patch
@@ -0,0 +1,99 @@
+From e7fc348fed61518907205603a7d0d6038cecfa1f Mon Sep 17 00:00:00 2001
+From: Digital Dreamtime <clive.messer@digitaldreamtime.co.uk>
+Date: Thu, 4 Feb 2016 14:14:44 +0000
+Subject: [PATCH 143/156] Allow up to 24dB digital gain to be applied when
+ using IQAudIO DAC+
+
+24db_digital_gain DT param can be used to specify that PCM512x
+codec "Digital" volume control should not be limited to 0dB gain,
+and if specified will allow the full 24dB gain.
+---
+ arch/arm/boot/dts/overlays/README | 17 +++++++++++++++--
+ .../boot/dts/overlays/iqaudio-dacplus-overlay.dts | 6 +++++-
+ sound/soc/bcm/iqaudio-dac.c | 20 ++++++++++++++------
+ 3 files changed, 34 insertions(+), 9 deletions(-)
+
+--- a/arch/arm/boot/dts/overlays/README
++++ b/arch/arm/boot/dts/overlays/README
+@@ -362,8 +362,21 @@ Params: <None>
+
+ Name: iqaudio-dacplus
+ Info: Configures the IQaudio DAC+ audio card
+-Load: dtoverlay=iqaudio-dacplus
+-Params: <None>
++Load: dtoverlay=iqaudio-dacplus,<param>=<val>
++Params: 24db_digital_gain Allow gain to be applied via the PCM512x codec
++ Digital volume control. Enable with
++ "dtoverlay=iqaudio-dacplus,24db_digital_gain"
++ (The default behaviour is that the Digital
++ volume control is limited to a maximum of
++ 0dB. ie. it can attenuate but not provide
++ gain. For most users, this will be desired
++ as it will prevent clipping. By appending
++ the 24db_digital_gain parameter, the Digital
++ volume control will allow up to 24dB of
++ gain. If this parameter is enabled, it is the
++ responsibility of the user to ensure that
++ the Digital volume control is set to a value
++ that does not result in clipping/distortion!)
+
+
+ Name: lirc-rpi
+--- a/arch/arm/boot/dts/overlays/iqaudio-dacplus-overlay.dts
++++ b/arch/arm/boot/dts/overlays/iqaudio-dacplus-overlay.dts
+@@ -7,7 +7,7 @@
+
+ fragment@0 {
+ target = <&sound>;
+- __overlay__ {
++ frag0: __overlay__ {
+ compatible = "iqaudio,iqaudio-dac";
+ i2s-controller = <&i2s>;
+ status = "okay";
+@@ -36,4 +36,8 @@
+ };
+ };
+ };
++
++ __overrides__ {
++ 24db_digital_gain = <&frag0>,"iqaudio,24db_digital_gain?";
++ };
+ };
+--- a/sound/soc/bcm/iqaudio-dac.c
++++ b/sound/soc/bcm/iqaudio-dac.c
+@@ -23,14 +23,19 @@
+ #include <sound/soc.h>
+ #include <sound/jack.h>
+
++static bool digital_gain_0db_limit = true;
++
+ static int snd_rpi_iqaudio_dac_init(struct snd_soc_pcm_runtime *rtd)
+ {
+- int ret;
+- struct snd_soc_card *card = rtd->card;
+-
+- ret = snd_soc_limit_volume(card, "Digital Playback Volume", 207);
+- if (ret < 0)
+- dev_warn(card->dev, "Failed to set volume limit: %d\n", ret);
++ if (digital_gain_0db_limit)
++ {
++ int ret;
++ struct snd_soc_card *card = rtd->card;
++
++ ret = snd_soc_limit_volume(card, "Digital Playback Volume", 207);
++ if (ret < 0)
++ dev_warn(card->dev, "Failed to set volume limit: %d\n", ret);
++ }
+
+ return 0;
+ }
+@@ -94,6 +99,9 @@ static int snd_rpi_iqaudio_dac_probe(str
+ dai->platform_name = NULL;
+ dai->platform_of_node = i2s_node;
+ }
++
++ digital_gain_0db_limit = !of_property_read_bool(pdev->dev.of_node,
++ "iqaudio,24db_digital_gain");
+ }
+
+ ret = snd_soc_register_card(&snd_rpi_iqaudio_dac);