Add WM8960 soundcard support

Signed-off-by: Devendra Tewari <devendra.tewari@gmail.com>

conf/machine/include/rpi-base.inc

@@ -50,6 +50,7 @@ RPI_KERNEL_DEVICETREE_OVERLAYS ?= " \
     overlays/vc4-kms-dsi-7inch.dtbo \
     overlays/w1-gpio.dtbo \
     overlays/w1-gpio-pullup.dtbo \
+    overlays/wm8960-soundcard.dtbo \
     "
 
 RPI_KERNEL_DEVICETREE ?= " \

docs/extra-build-config.md

@@ -349,3 +349,24 @@ Also, this will enable adding Contiguous Memory Allocation value in the cmdline.
 Ref.:
 * <https://github.com/raspberrypi/documentation/blob/master/linux/software/libcamera/README.md>
 * <https://www.raspberrypi.org/blog/an-open-source-camera-stack-for-raspberry-pi-using-libcamera/>
+
+## WM8960 soundcard support
+
+Support for WM8960 based sound cards such as the WM8960 Hi-Fi Sound Card HAT for Raspberry Pi from Waveshare, and ReSpeaker 2 / 4 / 6 Mics Pi HAT from Seeed Studio, can be enabled in `local.conf`
+
+    ```conf
+    MACHINE_FEATURES += "wm8960"
+    ```
+
+You may need to adjust volume and toggle switches that are off by default
+
+    ```bash
+    amixer -c1 sset 'Headphone',0 80%,80%
+    amixer -c1 sset 'Speaker',0 80%,80%
+    amixer -c1 sset 'Left Input Mixer Boost' toggle
+    amixer -c1 sset 'Left Output Mixer PCM' toggle
+    amixer -c1 sset 'Right Input Mixer Boost' toggle
+    amixer -c1 sset 'Right Output Mixer PCM' toggle
+    ```
+
+Audio capture on ReSpeaker 2 / 4 / 6 Mics Pi HAT from Seeed Studio is very noisy.

recipes-bsp/bootfiles/rpi-config_git.bb

@@ -30,6 +30,8 @@ GPIO_IR_TX ?= "17"
 
 CAN_OSCILLATOR ?= "16000000"
 
+WM8960="${@bb.utils.contains("MACHINE_FEATURES", "wm8960", "1", "0", d)}"
+
 inherit deploy nopackages
 
 do_deploy() {
@@ -251,6 +253,12 @@ do_deploy() {
                 ;;
         esac
     fi
+
+    # WM8960 support
+    if [ "${WM8960}" = "1" ]; then
+        echo "# Enable WM8960" >> $CONFIG
+        echo "dtoverlay=wm8960-soundcard" >> $CONFIG
+    fi
 }
 
 do_deploy_append_raspberrypi3-64() {

recipes-kernel/linux/files/wm8960.cfg

@@ -0,0 +1,2 @@
+CONFIG_I2C_BCM2835=y
+CONFIG_SND_SOC_WM8960=y

recipes-kernel/linux/linux-raspberrypi.inc

@@ -14,6 +14,7 @@ require recipes-kernel/linux/linux-yocto.inc
 SRC_URI += " \
     ${@bb.utils.contains("INITRAMFS_IMAGE_BUNDLE", "1", "file://initramfs-image-bundle.cfg", "", d)} \
     ${@bb.utils.contains("MACHINE_FEATURES", "vc4graphics", "file://vc4graphics.cfg", "", d)} \
+    ${@bb.utils.contains("MACHINE_FEATURES", "wm8960", "file://wm8960.cfg", "", d)} \
     "
 
 KCONFIG_MODE = "--alldefconfig"