Allo Piano DAC boards: Initial 2 channel (stereo) support (#1645)

Add initial 2 channel (stereo) support for Allo Piano DAC (2.0/2.1) boards,
using allo-piano-dac-pcm512x-audio overlay and allo-piano-dac ALSA ASoC
machine driver.

NB. The initial support is 2 channel (stereo) ONLY!
(The Piano DAC 2.1 will only support 2 channel (stereo) left/right output,
 pending an update to the upstream pcm512x codec driver, which will have
 to be submitted via upstream. With the initial downstream support,
 provided by this patch, the Piano DAC 2.1 subwoofer outputs will
 not function.)

Signed-off-by: Baswaraj K <[email protected]>
Signed-off-by: Clive Messer <[email protected]>
Tested-by: Clive Messer <[email protected]>

sound/soc/bcm/Kconfig

@@ -116,3 +116,10 @@ config SND_BCM2708_SOC_DIONAUDIO_LOCO
 	select SND_SOC_PCM5102a
 	help
 	  Say Y or M if you want to add support for Dion Audio LOCO.
+
+config SND_BCM2708_SOC_ALLO_PIANO_DAC
+	tristate "Support for Allo Piano DAC"
+	depends on SND_BCM2708_SOC_I2S || SND_BCM2835_SOC_I2S
+	select SND_SOC_PCM512x_I2C
+	help
+	  Say Y or M if you want to add support for Allo Piano DAC.

sound/soc/bcm/Makefile

@@ -23,6 +23,7 @@ snd-soc-raspidac3-objs := raspidac3.o
 snd-soc-audioinjector-pi-soundcard-objs := audioinjector-pi-soundcard.o
 snd-soc-digidac1-soundcard-objs := digidac1-soundcard.o
 snd-soc-dionaudio-loco-objs := dionaudio_loco.o
+snd-soc-allo-piano-dac-objs := allo-piano-dac.o
 
 obj-$(CONFIG_SND_BCM2708_SOC_ADAU1977_ADC) += snd-soc-adau1977-adc.o
 obj-$(CONFIG_SND_BCM2708_SOC_HIFIBERRY_DAC) += snd-soc-hifiberry-dac.o
@@ -38,3 +39,4 @@ obj-$(CONFIG_SND_BCM2708_SOC_RASPIDAC3) += snd-soc-raspidac3.o
 obj-$(CONFIG_SND_AUDIOINJECTOR_PI_SOUNDCARD) += snd-soc-audioinjector-pi-soundcard.o
 obj-$(CONFIG_SND_DIGIDAC1_SOUNDCARD) += snd-soc-digidac1-soundcard.o
 obj-$(CONFIG_SND_BCM2708_SOC_DIONAUDIO_LOCO) += snd-soc-dionaudio-loco.o
+obj-$(CONFIG_SND_BCM2708_SOC_ALLO_PIANO_DAC) += snd-soc-allo-piano-dac.o

sound/soc/bcm/allo-piano-dac.c

@@ -0,0 +1,144 @@
+/*
+ * ALSA ASoC Machine Driver for Allo Piano DAC
+ *
+ * Author:	Baswaraj K <[email protected]>
+ *		Copyright 2016
+ *		based on code by Daniel Matuschek <[email protected]>
+ *		based on code by Florian Meier <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+#include <sound/core.h>
+#include <sound/pcm.h>
+#include <sound/pcm_params.h>
+#include <sound/soc.h>
+
+static bool digital_gain_0db_limit = true;
+
+static int snd_allo_piano_dac_init(struct snd_soc_pcm_runtime *rtd)
+{
+	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;
+}
+
+static int snd_allo_piano_dac_hw_params(
+	struct snd_pcm_substream *substream, struct snd_pcm_hw_params *params)
+{
+	struct snd_soc_pcm_runtime *rtd = substream->private_data;
+	struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
+
+	unsigned int sample_bits =
+		snd_pcm_format_physical_width(params_format(params));
+
+	return snd_soc_dai_set_bclk_ratio(cpu_dai, sample_bits * 2);
+}
+
+/* machine stream operations */
+static struct snd_soc_ops snd_allo_piano_dac_ops = {
+	.hw_params = snd_allo_piano_dac_hw_params,
+};
+
+static struct snd_soc_dai_link snd_allo_piano_dac_dai[] = {
+{
+	.name		= "Piano DAC",
+	.stream_name	= "Piano DAC HiFi",
+	.cpu_dai_name	= "bcm2708-i2s.0",
+	.codec_dai_name	= "pcm512x-hifi",
+	.platform_name	= "bcm2708-i2s.0",
+	.codec_name	= "pcm512x.1-004c",
+	.dai_fmt	= SND_SOC_DAIFMT_I2S |
+			  SND_SOC_DAIFMT_NB_NF |
+			  SND_SOC_DAIFMT_CBS_CFS,
+	.ops		= &snd_allo_piano_dac_ops,
+	.init		= snd_allo_piano_dac_init,
+},
+};
+
+/* audio machine driver */
+static struct snd_soc_card snd_allo_piano_dac = {
+	.name         = "PianoDAC",
+	.owner        = THIS_MODULE,
+	.dai_link     = snd_allo_piano_dac_dai,
+	.num_links    = ARRAY_SIZE(snd_allo_piano_dac_dai),
+};
+
+static int snd_allo_piano_dac_probe(struct platform_device *pdev)
+{
+	int ret = 0;
+
+	snd_allo_piano_dac.dev = &pdev->dev;
+
+	if (pdev->dev.of_node) {
+		struct device_node *i2s_node;
+		struct snd_soc_dai_link *dai;
+
+		dai = &snd_allo_piano_dac_dai[0];
+		i2s_node = of_parse_phandle(pdev->dev.of_node,
+					    "i2s-controller", 0);
+
+		if (i2s_node) {
+			dai->cpu_dai_name = NULL;
+			dai->cpu_of_node = i2s_node;
+			dai->platform_name = NULL;
+			dai->platform_of_node = i2s_node;
+		}
+
+		digital_gain_0db_limit = !of_property_read_bool(
+			pdev->dev.of_node, "allo,24db_digital_gain");
+	}
+
+	ret = snd_soc_register_card(&snd_allo_piano_dac);
+	if (ret)
+		dev_err(&pdev->dev,
+			"snd_soc_register_card() failed: %d\n", ret);
+
+	return ret;
+}
+
+static int snd_allo_piano_dac_remove(struct platform_device *pdev)
+{
+	return snd_soc_unregister_card(&snd_allo_piano_dac);
+}
+
+static const struct of_device_id snd_allo_piano_dac_of_match[] = {
+	{ .compatible = "allo,piano-dac", },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, snd_allo_piano_dac_of_match);
+
+static struct platform_driver snd_allo_piano_dac_driver = {
+	.driver = {
+		.name   = "snd-allo-piano-dac",
+		.owner  = THIS_MODULE,
+		.of_match_table = snd_allo_piano_dac_of_match,
+	},
+	.probe          = snd_allo_piano_dac_probe,
+	.remove         = snd_allo_piano_dac_remove,
+};
+
+module_platform_driver(snd_allo_piano_dac_driver);
+
+MODULE_AUTHOR("Baswaraj K <[email protected]>");
+MODULE_DESCRIPTION("ALSA ASoC Machine Driver for Allo Piano DAC");
+MODULE_LICENSE("GPL v2");