BCM270X_DT: Add pwm and pwm-2chan overlays

From the README entries: Legal pin,function combinations for each channel: PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0) 52,5(Alt1) PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1) N.B.: 1) Pin 18 is the only one available on all platforms, and it is the one used by the I2S audio interface. Pins 12 and 13 might be better choices on an A+, B+ or Pi2. 2) The onboard analogue audio output uses both PWM channels. 3) So be careful mixing audio and PWM. 4) Currently the clock must have been enabled and configured by other means. See: #756
raspberrypi · Aug 19, 2015 · 8bbf4b5 · 8bbf4b5
1 parent d657cbb
commit 8bbf4b5
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diff --git a/arch/arm/boot/dts/bcm2708_common.dtsi b/arch/arm/boot/dts/bcm2708_common.dtsi
@@ -154,6 +154,14 @@
 			status = "disabled";
 		};
 
+		pwm: pwm@7e20c000 {
+			compatible = "brcm,bcm2835-pwm";
+			reg = <0x7e20c000 0x28>;
+			clocks = <&clk_pwm>;
+			#pwm-cells = <2>;
+			status = "disabled";
+		};
+
 		uart1: uart@7e215040 {
 			compatible = "brcm,bcm2835-aux-uart", "ns16550";
 			reg = <0x7e215040 0x40>;
@@ -279,6 +287,14 @@
 			clock-output-names = "apb_pclk";
 			clock-frequency = <126000000>;
 		};
+
+		clk_pwm: clock@5 {
+			 compatible = "fixed-clock";
+			 reg = <3>;
+			 #clock-cells = <0>;
+			 clock-output-names = "pwm";
+			 clock-frequency = <100000000>;
+		};
 	};
 
 	__overrides__ {

diff --git a/arch/arm/boot/dts/overlays/Makefile b/arch/arm/boot/dts/overlays/Makefile
@@ -35,6 +35,8 @@ dtb-$(RPI_DT_OVERLAYS) += mz61581-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += piscreen-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += pitft28-resistive-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += pps-gpio-overlay.dtb
+dtb-$(RPI_DT_OVERLAYS) += pwm-overlay.dtb
+dtb-$(RPI_DT_OVERLAYS) += pwm-2chan-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += rpi-dac-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += rpi-display-overlay.dtb
 dtb-$(RPI_DT_OVERLAYS) += rpi-ft5406-overlay.dtb

diff --git a/arch/arm/boot/dts/overlays/README b/arch/arm/boot/dts/overlays/README
@@ -410,6 +410,47 @@ Load:   dtoverlay=pps-gpio,<param>=<val>
 Params: gpiopin                  Input GPIO (default "18")
 
 
+Name:   pwm
+Info:   Configures a single PWM channel
+        Legal pin,function combinations for each channel:
+          PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0)            52,5(Alt1)
+          PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1)
+        N.B.:
+          1) Pin 18 is the only one available on all platforms, and
+             it is the one used by the I2S audio interface.
+             Pins 12 and 13 might be better choices on an A+, B+ or Pi2.
+          2) The onboard analogue audio output uses both PWM channels.
+          3) So be careful mixing audio and PWM.
+          4) Currently the clock must have been enabled and configured
+             by other means.
+Load:   dtoverlay=pwm-2chan,<param>=<val>
+Load:   dtoverlay=pwm,<param>=<val>
+Params: pin                      Output pin (default 18) - see table
+        func                     Pin function (default 2 = Alt5) - see above
+        clock                    PWM clock frequency (informational)
+
+
+Name:   pwm-2chan
+Info:   Configures both PWM channels
+        Legal pin,function combinations for each channel:
+          PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0)            52,5(Alt1)
+          PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1)
+        N.B.:
+          1) Pin 18 is the only one available on all platforms, and
+             it is the one used by the I2S audio interface.
+             Pins 12 and 13 might be better choices on an A+, B+ or Pi2.
+          2) The onboard analogue audio output uses both PWM channels.
+          3) So be careful mixing audio and PWM.
+          4) Currently the clock must have been enabled and configured
+             by other means.
+Load:   dtoverlay=pwm-2chan,<param>=<val>
+Params: pin                      Output pin (default 18) - see table
+        pin2                     Output pin for other channel (default 19)
+        func                     Pin function (default 2 = Alt5) - see above
+        func2                    Function for pin2 (default 2 = Alt5)
+        clock                    PWM clock frequency (informational)
+
+
 Name:   rpi-dac
 Info:   Configures the RPi DAC audio card
 Load:   dtoverlay=rpi-dac

diff --git a/arch/arm/boot/dts/overlays/pwm-2chan-overlay.dts b/arch/arm/boot/dts/overlays/pwm-2chan-overlay.dts
@@ -0,0 +1,46 @@
+/dts-v1/;
+/plugin/;
+
+/*
+This is the 2-channel overlay - only use it if you need both channels.
+
+Legal pin,function combinations for each channel:
+  PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0)            52,5(Alt1)
+  PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1)
+
+N.B.:
+  1) Pin 18 is the only one available on all platforms, and
+     it is the one used by the I2S audio interface.
+     Pins 12 and 13 might be better choices on an A+, B+ or Pi2.
+  2) The onboard analogue audio output uses both PWM channels.
+  3) So be careful mixing audio and PWM.
+*/
+
+/ {
+	fragment@0 {
+		target = <&gpio>;
+		__overlay__ {
+			pwm_pins: pwm_pins {
+				brcm,pins = <18 19>;
+				brcm,function = <2 2>; /* Alt5 */
+			};
+		};
+	};
+
+	fragment@1 {
+		target = <&pwm>;
+		__overlay__ {
+			pinctrl-names = "default";
+			pinctrl-0 = <&pwm_pins>;
+			status = "okay";
+		};
+	};
+
+	__overrides__ {
+		pin   = <&pwm_pins>,"brcm,pins:0";
+		pin2  = <&pwm_pins>,"brcm,pins:4";
+		func  = <&pwm_pins>,"brcm,function:0";
+		func2 = <&pwm_pins>,"brcm,function:4";
+		clock = <&clk_pwm>,"clock-frequency:0";
+	};
+};
diff --git a/arch/arm/boot/dts/overlays/pwm-overlay.dts b/arch/arm/boot/dts/overlays/pwm-overlay.dts
@@ -0,0 +1,42 @@
+/dts-v1/;
+/plugin/;
+
+/*
+Legal pin,function combinations for each channel:
+  PWM0: 12,4(Alt0) 18,2(Alt5) 40,4(Alt0)            52,5(Alt1)
+  PWM1: 13,4(Alt0) 19,2(Alt5) 41,4(Alt0) 45,4(Alt0) 53,5(Alt1)
+
+N.B.:
+  1) Pin 18 is the only one available on all platforms, and
+     it is the one used by the I2S audio interface.
+     Pins 12 and 13 might be better choices on an A+, B+ or Pi2.
+  2) The onboard analogue audio output uses both PWM channels.
+  3) So be careful mixing audio and PWM.
+*/
+
+/ {
+	fragment@0 {
+		target = <&gpio>;
+		__overlay__ {
+			pwm_pins: pwm_pins {
+				brcm,pins = <18>;
+				brcm,function = <2>; /* Alt5 */
+			};
+		};
+	};
+
+	fragment@1 {
+		target = <&pwm>;
+		__overlay__ {
+			pinctrl-names = "default";
+			pinctrl-0 = <&pwm_pins>;
+			status = "okay";
+		};
+	};
+
+	__overrides__ {
+		pin   = <&pwm_pins>,"brcm,pins:0";
+		func  = <&pwm_pins>,"brcm,function:0";
+		clock = <&clk_pwm>,"clock-frequency:0";
+	};
+};
diff --git a/arch/arm/configs/bcm2709_defconfig b/arch/arm/configs/bcm2709_defconfig
@@ -1087,6 +1087,7 @@ CONFIG_IIO_BUFFER=y
 CONFIG_IIO_BUFFER_CB=y
 CONFIG_IIO_KFIFO_BUF=m
 CONFIG_DHT11=m
+CONFIG_PWM_BCM2835=m
 CONFIG_RASPBERRYPI_FIRMWARE=y
 CONFIG_EXT4_FS=y
 CONFIG_EXT4_FS_POSIX_ACL=y

diff --git a/arch/arm/configs/bcmrpi_defconfig b/arch/arm/configs/bcmrpi_defconfig
@@ -1080,6 +1080,7 @@ CONFIG_IIO_BUFFER=y
 CONFIG_IIO_BUFFER_CB=y
 CONFIG_IIO_KFIFO_BUF=m
 CONFIG_DHT11=m
+CONFIG_PWM_BCM2835=m
 CONFIG_RASPBERRYPI_FIRMWARE=y
 CONFIG_EXT4_FS=y
 CONFIG_EXT4_FS_POSIX_ACL=y

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
@@ -85,7 +85,7 @@ config PWM_BCM_KONA
 
 config PWM_BCM2835
 	tristate "BCM2835 PWM support"
-	depends on ARCH_BCM2835
+	depends on ARCH_BCM2835 || ARCH_BCM2708 || ARCH_BCM2709
 	help
 	  PWM framework driver for BCM2835 controller (Raspberry Pi)