ASoC: bcm: add I2S MEMS Microphone driver

- https://github.com/adafruit/Raspberry-Pi-Installer-Scripts/tree/master/i2s_mic_module

arch/arm64/configs/bcm2711_defconfig

@@ -1037,7 +1037,7 @@ CONFIG_SND_USB_6FIRE=m
 CONFIG_SND_USB_HIFACE=m
 CONFIG_SND_USB_TONEPORT=m
 CONFIG_SND_SOC=y
-CONFIG_SND_BCM2835_SOC_I2S=m
+CONFIG_SND_BCM2835_SOC_I2S=y
 CONFIG_SND_BCM2708_SOC_CHIPDIP_DAC=m
 CONFIG_SND_BCM2708_SOC_GOOGLEVOICEHAT_SOUNDCARD=m
 CONFIG_SND_BCM2708_SOC_HIFIBERRY_DAC=m
@@ -1074,6 +1074,7 @@ CONFIG_SND_BCM2708_SOC_ALLO_BOSS2_DAC=m
 CONFIG_SND_BCM2708_SOC_ALLO_DIGIONE=m
 CONFIG_SND_BCM2708_SOC_ALLO_KATANA_DAC=m
 CONFIG_SND_BCM2708_SOC_FE_PI_AUDIO=m
+CONFIG_SND_BCM2708_SOC_I2SMIC_RPI=y
 CONFIG_SND_PISOUND=m
 CONFIG_SND_DACBERRY400=m
 CONFIG_SND_SOC_AD193X_SPI=m
@@ -1088,7 +1089,7 @@ CONFIG_SND_SOC_MAX98357A=m
 CONFIG_SND_SOC_SPDIF=m
 CONFIG_SND_SOC_WM8804_I2C=m
 CONFIG_SND_SOC_WM8960=m
-CONFIG_SND_SIMPLE_CARD=m
+CONFIG_SND_SIMPLE_CARD=y
 CONFIG_HID_BATTERY_STRENGTH=y
 CONFIG_HIDRAW=y
 CONFIG_UHID=m

sound/soc/bcm/Kconfig

@@ -307,6 +307,12 @@ config SND_BCM2708_SOC_FE_PI_AUDIO
 	help
 	  Say Y or M if you want to add support for Fe-Pi-Audio.
 
+config SND_BCM2708_SOC_I2SMIC_RPI
+        tristate "Support for I2S MEMS Microphone"
+        depends on SND_BCM2708_SOC_I2S || SND_BCM2835_SOC_I2S
+        help
+         Say Y or M if you want to add support for I2S MEMS Microphone.
+
 config SND_PISOUND
 	tristate "Support for Blokas Labs pisound"
 	depends on SND_BCM2708_SOC_I2S || SND_BCM2835_SOC_I2S

sound/soc/bcm/Makefile

@@ -49,6 +49,7 @@ snd-soc-rpi-wm8804-soundcard-objs := rpi-wm8804-soundcard.o
 snd-soc-pifi-40-objs := pifi-40.o
 snd-soc-chipdip-dac-objs := chipdip-dac.o
 snd-soc-dacberry400-objs := dacberry400.o
+snd-soc-i2smic-rpi-objs := snd-i2smic-rpi.o
 
 obj-$(CONFIG_SND_BCM2708_SOC_GOOGLEVOICEHAT_SOUNDCARD)  += snd-soc-googlevoicehat-codec.o
 obj-$(CONFIG_SND_BCM2708_SOC_HIFIBERRY_DACPLUS) += snd-soc-hifiberry-dacplus.o
@@ -82,3 +83,4 @@ obj-$(CONFIG_SND_RPI_WM8804_SOUNDCARD) += snd-soc-rpi-wm8804-soundcard.o
 obj-$(CONFIG_SND_BCM2708_SOC_PIFI_40) += snd-soc-pifi-40.o
 obj-$(CONFIG_SND_BCM2708_SOC_CHIPDIP_DAC) += snd-soc-chipdip-dac.o
 obj-$(CONFIG_SND_DACBERRY400) += snd-soc-dacberry400.o
+obj-$(CONFIG_SND_BCM2708_SOC_I2SMIC_RPI) += snd-soc-i2smic-rpi.o

sound/soc/bcm/snd-i2smic-rpi.c

@@ -0,0 +1,151 @@
+/*
+ * =====================================================================================
+ *
+ *       Filename:  snd-i2smic-rpi
+ *
+ *    Description:  I2S microphone kernel module
+ *
+ *        Version:  0.1.0
+ *        Created:  2020-04-14
+ *       Revision:  none
+ *       Compiler:  gcc
+ *
+ *       Pi4 Mods:  Carter Nelson
+ *    Orig Author:  Huan Truong (htruong@tnhh.net), originally written by Paul Creaser
+ *
+ * =====================================================================================
+ */
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/kernel.h>
+#include <linux/kmod.h>
+#include <linux/platform_device.h>
+#include <sound/simple_card.h>
+#include <linux/delay.h>
+#include "snd-i2smic-rpi.h"
+
+/*
+ * modified for linux 4.1.5
+ * inspired by https://github.com/msperl/spi-config
+ * with thanks for https://github.com/notro/rpi-source/wiki
+ * as well as Florian Meier for the rpi i2s and dma drivers
+ *
+ * to use a differant (simple-card compatible) codec
+ * change the codec name string in two places and the
+ * codec_dai name string. (see codec's source file)
+ *
+ *
+ * N.B. playback vs capture is determined by the codec choice
+ * */
+
+static struct asoc_simple_card_info card_info;
+static struct platform_device card_device;
+
+/*
+ * Setup command line parameter
+ */
+static short rpi_platform_generation = 2;
+module_param(rpi_platform_generation, short, 0);
+MODULE_PARM_DESC(rpi_platform_generation, "Raspberry Pi generation: 0=Pi0, 1=Pi2/3, 2=Pi4");
+
+/*
+ * Dummy callback for release
+ */
+void device_release_callback(struct device *dev) { /*  do nothing */ };
+
+/*
+ * Setup the card info
+ */
+static struct asoc_simple_card_info default_card_info = {
+  .card = "snd_rpi_i2s_card",       // -> snd_soc_card.name
+  .name = "simple-card_codec_link", // -> snd_soc_dai_link.name
+  .codec = "snd-soc-dummy",         // "dmic-codec", // -> snd_soc_dai_link.codec_name
+  .platform = "not-set.i2s",
+  .daifmt = SND_SOC_DAIFMT_I2S | SND_SOC_DAIFMT_NB_NF | SND_SOC_DAIFMT_CBS_CFS,
+  .cpu_dai = {
+    .name = "not-set.i2s",          // -> snd_soc_dai_link.cpu_dai_name
+    .sysclk = 0
+  },
+  .codec_dai = {
+    .name = "snd-soc-dummy-dai",    //"dmic-codec", // -> snd_soc_dai_link.codec_dai_name
+    .sysclk = 0
+  },
+};
+
+/*
+ * Setup the card device
+ */
+static struct platform_device default_card_device = {
+  .name = "asoc-simple-card",   //module alias
+  .id = 0,
+  .num_resources = 0,
+  .dev = {
+    .release = &device_release_callback,
+    .platform_data = &default_card_info, // *HACK ALERT*
+  },
+};
+
+/*
+ * Callback for module initialization
+ */
+int i2s_mic_rpi_init(void)
+{
+  const char *dmaengine = "bcm2708-dmaengine"; //module name
+  static char *card_platform;
+  int ret;
+
+  printk(KERN_INFO "snd-i2smic-rpi: Version %s\n", SND_I2SMIC_RPI_VERSION);
+
+  // Set platform
+  switch (rpi_platform_generation) {
+    case 0:
+      // Pi Zero
+      card_platform = "20203000.i2s";
+      break;
+    case 1:
+      // Pi 2 and 3
+      card_platform = "3f203000.i2s";
+      break;
+    case 2:
+    default:
+      // Pi 4
+      card_platform = "fe203000.i2s";
+      break;
+  }
+
+  printk(KERN_INFO "snd-i2smic-rpi: Setting platform to %s\n", card_platform);
+
+  // request DMA engine module
+  ret = request_module(dmaengine);
+  pr_alert("request module load '%s': %d\n",dmaengine, ret);
+
+  // update info
+  card_info = default_card_info;
+  card_info.platform = card_platform;
+  card_info.cpu_dai.name = card_platform;
+
+  card_device = default_card_device;
+  card_device.dev.platform_data = &card_info;
+
+  // register the card device
+  ret = platform_device_register(&card_device);
+  pr_alert("register platform device '%s': %d\n",card_device.name, ret);
+
+  return 0;
+}
+
+/*
+ * Callback for module exit
+ */
+void i2s_mic_rpi_exit(void)
+{
+  platform_device_unregister(&card_device);
+  pr_alert("i2s mic module unloaded\n");
+}
+
+// Plumb it up
+module_init(i2s_mic_rpi_init);
+module_exit(i2s_mic_rpi_exit);
+MODULE_DESCRIPTION("ASoC simple-card I2S Microphone");
+MODULE_AUTHOR("Carter Nelson");
+MODULE_LICENSE("GPL v2");

sound/soc/bcm/snd-i2smic-rpi.h

@@ -0,0 +1,6 @@
+#ifndef _SND_I2SMIC_RPI_H_
+#define _SND_I2SMIC_RPI_H_
+
+#define SND_I2SMIC_RPI_VERSION  "0.1.0"
+
+#endif