target/linux/brcm2708/patches-4.4/0323-Allow-up-to-24dB-digital-gain-to-be-applied-when-usi.patch

   1 From e38ba0616f674d2e78f8edd52f8fe770eb0e0a8e Mon Sep 17 00:00:00 2001
   2 From: DigitalDreamtime <clive.messer@digitaldreamtime.co.uk>
   3 Date: Fri, 6 May 2016 09:42:55 +0100
   4 Subject: [PATCH] Allow up to 24dB digital gain to be applied when using
   5  IQAudIO DAC
   6
   7 24db_digital_gain DT param can be used to specify that PCM512x
   8 codec "Digital" volume control should not be limited to 0dB gain,
   9 and if specified will allow the full 24dB gain.
  10
  11 Signed-off-by: DigitalDreamtime <clive.messer@digitaldreamtime.co.uk>
  12 ---
  13  arch/arm/boot/dts/overlays/README                  | 17 +++++++++++++++--
  14  arch/arm/boot/dts/overlays/iqaudio-dac-overlay.dts |  6 +++++-
  15  2 files changed, 20 insertions(+), 3 deletions(-)
  16
  17 --- a/arch/arm/boot/dts/overlays/README
  18 +++ b/arch/arm/boot/dts/overlays/README
  19 @@ -490,8 +490,21 @@ Params: <None>
  20
  21  Name:   iqaudio-dac
  22  Info:   Configures the IQaudio DAC audio card
  23 -Load:   dtoverlay=iqaudio-dac
  24 -Params: <None>
  25 +Load:   dtoverlay=iqaudio-dac,<param>
  26 +Params: 24db_digital_gain       Allow gain to be applied via the PCM512x codec
  27 +                                Digital volume control. Enable with
  28 +                                "dtoverlay=iqaudio-dac,24db_digital_gain"
  29 +                                (The default behaviour is that the Digital
  30 +                                volume control is limited to a maximum of
  31 +                                0dB. ie. it can attenuate but not provide
  32 +                                gain. For most users, this will be desired
  33 +                                as it will prevent clipping. By appending
  34 +                                the 24db_digital_gain parameter, the Digital
  35 +                                volume control will allow up to 24dB of
  36 +                                gain. If this parameter is enabled, it is the
  37 +                                responsibility of the user to ensure that
  38 +                                the Digital volume control is set to a value
  39 +                                that does not result in clipping/distortion!)
  40
  41
  42  Name:   iqaudio-dacplus
  43 --- a/arch/arm/boot/dts/overlays/iqaudio-dac-overlay.dts
  44 +++ b/arch/arm/boot/dts/overlays/iqaudio-dac-overlay.dts
  45 @@ -30,10 +30,14 @@
  46
  47         fragment@2 {
  48                 target = <&sound>;
  49 -               __overlay__ {
  50 +               frag2: __overlay__ {
  51                         compatible = "iqaudio,iqaudio-dac";
  52                         i2s-controller = <&i2s>;
  53                         status = "okay";
  54                 };
  55         };
  56 +
  57 +       __overrides__ {
  58 +               24db_digital_gain = <&frag2>,"iqaudio,24db_digital_gain?";
  59 +       };
  60  };