Add PIO-assisted WS2812 LEDs driver

arch/arm/boot/dts/overlays/Makefile

@@ -342,7 +342,8 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
 	waveshare-can-fd-hat-mode-a.dtbo \
 	waveshare-can-fd-hat-mode-b.dtbo \
 	wittypi.dtbo \
-	wm8960-soundcard.dtbo
+	wm8960-soundcard.dtbo \
+	ws2812-pio.dtbo
 
 targets += dtbs dtbs_install
 targets += $(dtbo-y)

arch/arm/boot/dts/overlays/README

@@ -5599,6 +5599,28 @@ Params: alsaname                Changes the card name in ALSA
         compatible              Changes the codec compatibility
 
 
+Name:   ws2812-pio
+Info:   Configures a GPIO pin to drive a string of WS2812 LEDS using pio. It
+        can be enabled on any RP1 GPIO in bank 0 (0-27). Up to 4 are supported,
+        assuming nothing else is using PIO. Pi 5 only.
+Load:   dtoverlay=ws2812-pio,<param>=<val>
+Params: brightness              Set the initial brightness for the LEDs. The
+                                brightness can be changed at runtime by writing
+                                a single byte to offset 0 of the device. Note
+                                that brightness is a multiplier for the pixel
+                                values, and only white pixels can reach the
+                                maximum visible brightness. (range 0-255,
+                                default 255)
+        dev_name                The name for the /dev/ device entry. Note that
+                                if the name includes '%d' it will be replaced
+                                by the instance number. (default 'leds%d')
+        gpio                    Output GPIO (0-27, default 4)
+        num_leds                Number of LEDs (default 60)
+        rgbw                    'rgbw=on' (or 'rgbw') indicates that each pixel
+                                includes a white LED as well as the usual red,
+                                green and blue. (default 'off')
+
+
 Troubleshooting
 ===============
 

arch/arm/boot/dts/overlays/ws2812-pio-overlay.dts

@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+// Device tree overlay for RP1 PIO WS2812 driver.
+/dts-v1/;
+/plugin/;
+
+/ {
+	compatible = "brcm,bcm2712";
+
+	fragment@0 {
+		target = <&gpio>;
+		__overlay__ {
+			ws2812_pio_pins: ws2812_pio_pins@4 {
+				brcm,pins = <4>; /* gpio 4 */
+				function = "pio";
+				bias-disable;
+			};
+		};
+	};
+
+	fragment@1 {
+		target-path = "/";
+		__overlay__ {
+			ws2812_pio: ws2812_pio@4 {
+				compatible = "raspberrypi,ws2812-pio-rp1";
+				pinctrl-names = "default";
+				pinctrl-0 = <&ws2812_pio_pins>;
+				dev-name = "leds%d";
+				leds-gpios = <&gpio 4 0>;
+				rpi,num-leds = <60>;
+				rpi,brightness = <255>;
+			};
+		};
+	};
+
+	__overrides__ {
+		brightness = <&ws2812_pio>, "rpi,brightness:0";
+		dev_name = <&ws2812_pio>, "dev-name";
+		gpio = <&ws2812_pio>,"leds-gpios:4",
+		       <&ws2812_pio_pins>,"brcm,pins:0",
+		       /* modify reg values to allow multiple instantiation */
+		       <&ws2812_pio>,"reg:0",
+		       <&ws2812_pio_pins>,"reg:0";
+		num_leds = <&ws2812_pio>, "rpi,num-leds:0";
+		rgbw = <&ws2812_pio>, "rpi,rgbw?";
+	};
+};

arch/arm64/configs/bcm2711_defconfig

@@ -455,6 +455,7 @@ CONFIG_DEVTMPFS=y
 CONFIG_DEVTMPFS_MOUNT=y
 # CONFIG_BRCMSTB_GISB_ARB is not set
 CONFIG_RASPBERRYPI_FIRMWARE=y
+CONFIG_FIRMWARE_RP1=m
 # CONFIG_EFI_VARS_PSTORE is not set
 CONFIG_MTD=m
 CONFIG_MTD_BLOCK=m
@@ -475,6 +476,7 @@ CONFIG_BLK_DEV_RBD=m
 CONFIG_BLK_DEV_NVME=y
 CONFIG_NVME_HWMON=y
 CONFIG_RP1_PIO=m
+CONFIG_WS2812_PIO_RP1=m
 CONFIG_SRAM=y
 CONFIG_EEPROM_AT24=m
 CONFIG_EEPROM_AT25=m

arch/arm64/configs/bcm2712_defconfig

@@ -458,6 +458,7 @@ CONFIG_DEVTMPFS=y
 CONFIG_DEVTMPFS_MOUNT=y
 # CONFIG_BRCMSTB_GISB_ARB is not set
 CONFIG_RASPBERRYPI_FIRMWARE=y
+CONFIG_FIRMWARE_RP1=m
 # CONFIG_EFI_VARS_PSTORE is not set
 CONFIG_MTD=m
 CONFIG_MTD_BLOCK=m
@@ -478,6 +479,7 @@ CONFIG_BLK_DEV_RBD=m
 CONFIG_BLK_DEV_NVME=y
 CONFIG_NVME_HWMON=y
 CONFIG_RP1_PIO=m
+CONFIG_WS2812_PIO_RP1=m
 CONFIG_SRAM=y
 CONFIG_EEPROM_AT24=m
 CONFIG_EEPROM_AT25=m

drivers/misc/Kconfig

@@ -19,12 +19,22 @@ config BCM2835_SMI
 
 config RP1_PIO
 	tristate "Raspberry Pi RP1 PIO driver"
-	select FIRMWARE_RP1
+	depends on FIRMWARE_RP1 || COMPILE_TEST
 	default n
 	help
 		Driver providing control of the Raspberry Pi PIO block, as found in
 		RP1.
 
+config WS2812_PIO_RP1
+	tristate "Raspberry Pi PIO-base WS2812 driver"
+	depends on RP1_PIO || COMPILE_TEST
+	default n
+	help
+		Driver for the WS2812 (NeoPixel) LEDs using the RP1 PIO hardware.
+		The driver creates a character device to which rgbw pixels may be
+		written. Single-byte writes to offset 0 set the brightness at
+		runtime.
+
 config AD525X_DPOT
 	tristate "Analog Devices Digital Potentiometers"
 	depends on (I2C || SPI) && SYSFS

drivers/misc/Makefile

@@ -19,6 +19,7 @@ obj-$(CONFIG_PHANTOM)		+= phantom.o
 obj-$(CONFIG_QCOM_COINCELL)	+= qcom-coincell.o
 obj-$(CONFIG_QCOM_FASTRPC)	+= fastrpc.o
 obj-$(CONFIG_RP1_PIO)		+= rp1-pio.o
+obj-$(CONFIG_WS2812_PIO_RP1)	+= ws2812-pio-rp1.o
 obj-$(CONFIG_SENSORS_BH1770)	+= bh1770glc.o
 obj-$(CONFIG_SENSORS_APDS990X)	+= apds990x.o
 obj-$(CONFIG_ENCLOSURE_SERVICES) += enclosure.o