target/linux/brcm2708/patches-4.4/0141-Limit-PCM512x-Digital-gain-to-0dB-by-default-with-Hi.patch

   1 From 3f38eac723b07d22f70a77ae006d18eb84218a9e Mon Sep 17 00:00:00 2001
   2 From: Digital Dreamtime <clive.messer@digitaldreamtime.co.uk>
   3 Date: Thu, 4 Feb 2016 20:04:00 +0000
   4 Subject: [PATCH] Limit PCM512x "Digital" gain to 0dB by default with HiFiBerry
   5  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  .../arm/boot/dts/overlays/hifiberry-dacplus-overlay.dts |  6 +++++-
  13  sound/soc/bcm/hifiberry_dacplus.c                       | 14 ++++++++++++++
  14  3 files changed, 34 insertions(+), 3 deletions(-)
  15
  16 --- a/arch/arm/boot/dts/overlays/README
  17 +++ b/arch/arm/boot/dts/overlays/README
  18 @@ -273,8 +273,21 @@ Params: <None>
  19
  20  Name:   hifiberry-dacplus
  21  Info:   Configures the HifiBerry DAC+ audio card
  22 -Load:   dtoverlay=hifiberry-dacplus
  23 -Params: <None>
  24 +Load:   dtoverlay=hifiberry-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=hifiberry-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:   hifiberry-digi
  42 --- a/arch/arm/boot/dts/overlays/hifiberry-dacplus-overlay.dts
  43 +++ b/arch/arm/boot/dts/overlays/hifiberry-dacplus-overlay.dts
  44 @@ -17,7 +17,7 @@
  45
  46         fragment@1 {
  47                 target = <&sound>;
  48 -               __overlay__ {
  49 +               frag1: __overlay__ {
  50                         compatible = "hifiberry,hifiberry-dacplus";
  51                         i2s-controller = <&i2s>;
  52                         status = "okay";
  53 @@ -47,4 +47,8 @@
  54                         };
  55                 };
  56         };
  57 +
  58 +       __overrides__ {
  59 +               24db_digital_gain = <&frag1>,"hifiberry,24db_digital_gain?";
  60 +       };
  61  };
  62 --- a/sound/soc/bcm/hifiberry_dacplus.c
  63 +++ b/sound/soc/bcm/hifiberry_dacplus.c
  64 @@ -48,6 +48,7 @@ struct pcm512x_priv {
  65  #define CLK_48EN_RATE 24576000UL
  66
  67  static bool snd_rpi_hifiberry_is_dacpro;
  68 +static bool digital_gain_0db_limit = true;
  69
  70  static void snd_rpi_hifiberry_dacplus_select_clk(struct snd_soc_codec *codec,
  71         int clk_id)
  72 @@ -167,6 +168,16 @@ static int snd_rpi_hifiberry_dacplus_ini
  73         snd_soc_update_bits(codec, PCM512x_GPIO_OUTPUT_4, 0x0f, 0x02);
  74         snd_soc_update_bits(codec, PCM512x_GPIO_CONTROL_1, 0x08, 0x08);
  75
  76 +       if (digital_gain_0db_limit)
  77 +       {
  78 +               int ret;
  79 +               struct snd_soc_card *card = rtd->card;
  80 +
  81 +               ret = snd_soc_limit_volume(card, "Digital Playback Volume", 207);
  82 +               if (ret < 0)
  83 +                       dev_warn(card->dev, "Failed to set volume limit: %d\n", ret);
  84 +       }
  85 +
  86         return 0;
  87  }
  88
  89 @@ -299,6 +310,9 @@ static int snd_rpi_hifiberry_dacplus_pro
  90                         dai->platform_name = NULL;
  91                         dai->platform_of_node = i2s_node;
  92                 }
  93 +
  94 +               digital_gain_0db_limit = !of_property_read_bool(
  95 +                       pdev->dev.of_node, "hifiberry,24db_digital_gain");
  96         }
  97
  98         ret = snd_soc_register_card(&snd_rpi_hifiberry_dacplus);