target/linux/brcm2708/patches-4.4/0143-Allow-up-to-24dB-digital-gain-to-be-applied-when-usi.patch

   1 From e7fc348fed61518907205603a7d0d6038cecfa1f Mon Sep 17 00:00:00 2001
   2 From: Digital Dreamtime <clive.messer@digitaldreamtime.co.uk>
   3 Date: Thu, 4 Feb 2016 14:14:44 +0000
   4 Subject: [PATCH 143/156] Allow up to 24dB digital gain to be applied when
   5  using 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  arch/arm/boot/dts/overlays/README                    | 17 +++++++++++++++--
  12  .../boot/dts/overlays/iqaudio-dacplus-overlay.dts    |  6 +++++-
  13  sound/soc/bcm/iqaudio-dac.c                          | 20 ++++++++++++++------
  14  3 files changed, 34 insertions(+), 9 deletions(-)
  15
  16 --- a/arch/arm/boot/dts/overlays/README
  17 +++ b/arch/arm/boot/dts/overlays/README
  18 @@ -362,8 +362,21 @@ Params: <None>
  19
  20  Name:   iqaudio-dacplus
  21  Info:   Configures the IQaudio DAC+ audio card
  22 -Load:   dtoverlay=iqaudio-dacplus
  23 -Params: <None>
  24 +Load:   dtoverlay=iqaudio-dacplus,<param>=<val>
  25 +Params: 24db_digital_gain       Allow gain to be applied via the PCM512x codec
  26 +                                Digital volume control. Enable with
  27 +                                "dtoverlay=iqaudio-dacplus,24db_digital_gain"
  28 +                                (The default behaviour is that the Digital
  29 +                                volume control is limited to a maximum of
  30 +                                0dB. ie. it can attenuate but not provide
  31 +                                gain. For most users, this will be desired
  32 +                                as it will prevent clipping. By appending
  33 +                                the 24db_digital_gain parameter, the Digital
  34 +                                volume control will allow up to 24dB of
  35 +                                gain. If this parameter is enabled, it is the
  36 +                                responsibility of the user to ensure that
  37 +                                the Digital volume control is set to a value
  38 +                                that does not result in clipping/distortion!)
  39
  40
  41  Name:   lirc-rpi
  42 --- a/arch/arm/boot/dts/overlays/iqaudio-dacplus-overlay.dts
  43 +++ b/arch/arm/boot/dts/overlays/iqaudio-dacplus-overlay.dts
  44 @@ -7,7 +7,7 @@
  45
  46         fragment@0 {
  47                 target = <&sound>;
  48 -               __overlay__ {
  49 +               frag0: __overlay__ {
  50                         compatible = "iqaudio,iqaudio-dac";
  51                         i2s-controller = <&i2s>;
  52                         status = "okay";
  53 @@ -36,4 +36,8 @@
  54                         };
  55                 };
  56         };
  57 +
  58 +       __overrides__ {
  59 +               24db_digital_gain = <&frag0>,"iqaudio,24db_digital_gain?";
  60 +       };
  61  };
  62 --- a/sound/soc/bcm/iqaudio-dac.c
  63 +++ b/sound/soc/bcm/iqaudio-dac.c
  64 @@ -23,14 +23,19 @@
  65  #include <sound/soc.h>
  66  #include <sound/jack.h>
  67
  68 +static bool digital_gain_0db_limit = true;
  69 +
  70  static int snd_rpi_iqaudio_dac_init(struct snd_soc_pcm_runtime *rtd)
  71  {
  72 -       int ret;
  73 -       struct snd_soc_card *card = rtd->card;
  74 -
  75 -       ret = snd_soc_limit_volume(card, "Digital Playback Volume", 207);
  76 -       if (ret < 0)
  77 -               dev_warn(card->dev, "Failed to set volume limit: %d\n", ret);
  78 +       if (digital_gain_0db_limit)
  79 +       {
  80 +               int ret;
  81 +               struct snd_soc_card *card = rtd->card;
  82 +
  83 +               ret = snd_soc_limit_volume(card, "Digital Playback Volume", 207);
  84 +               if (ret < 0)
  85 +                       dev_warn(card->dev, "Failed to set volume limit: %d\n", ret);
  86 +       }
  87
  88         return 0;
  89  }
  90 @@ -94,6 +99,9 @@ static int snd_rpi_iqaudio_dac_probe(str
  91                 dai->platform_name = NULL;
  92                 dai->platform_of_node = i2s_node;
  93             }
  94 +
  95 +           digital_gain_0db_limit = !of_property_read_bool(pdev->dev.of_node,
  96 +                                       "iqaudio,24db_digital_gain");
  97         }
  98
  99         ret = snd_soc_register_card(&snd_rpi_iqaudio_dac);