Apple M1 FPWM (MacBook Pro keyboard backlight) driver

Documentation/devicetree/bindings/pwm/apple,fpwm.yaml

@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/pwm/apple,fpwm.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Apple M1 FPWM controller
+
+maintainers:
+  - Pip Cet <pipcet@gmail.com>
+
+description:
+  Single-channel PWM connected to the keyboard backlight on at least
+  some MacBook Pros.
+
+allOf:
+  - $ref: pwm.yaml#
+
+properties:
+  compatible:
+    const: apple,t8103-fpwm
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  "#pwm-cells":
+    const: 0
+
+additionalProperties: false
+
+required:
+  - reg
+  - clocks
+
+examples:
+  - |
+    pwm@235044000 {
+        compatible = "apple,t8103-fpwm";
+        reg = <0x35044000 0x4000>;
+        clocks = <&fpwm0_clk>;
+        #pwm-cells = <0>;
+    };

MAINTAINERS

@@ -1702,8 +1702,10 @@ T:	git https://github.com/AsahiLinux/linux.git
 F:	Documentation/devicetree/bindings/arm/apple.yaml
 F:	Documentation/devicetree/bindings/interrupt-controller/apple,aic.yaml
 F:	Documentation/devicetree/bindings/pinctrl/apple,pinctrl.yaml
+F:	Documentation/devicetree/bindings/pwm/apple,fpwm.yaml
 F:	arch/arm64/boot/dts/apple/
 F:	drivers/irqchip/irq-apple-aic.c
+F:	drivers/pwm/pwm-apple-m1.c
 F:	include/dt-bindings/interrupt-controller/apple-aic.h
 F:	include/dt-bindings/pinctrl/apple.h
 

arch/arm64/boot/dts/apple/Makefile

@@ -1,2 +1,2 @@
 # SPDX-License-Identifier: GPL-2.0
-dtb-$(CONFIG_ARCH_APPLE) += t8103-j274.dtb
+dtb-$(CONFIG_ARCH_APPLE) += t8103-j274.dtb t8103-j293.dtb

arch/arm64/boot/dts/apple/t8103-j293.dts

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0+ OR MIT
+/*
+ * Apple MacBook Pro (13-inch, M1, 2020)
+ *
+ * target-type: J293
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+/dts-v1/;
+
+#include "t8103.dtsi"
+
+/ {
+	compatible = "apple,j293", "apple,t8103", "apple,arm-platform";
+	model = "Apple MacBook Pro (13-inch, M1, 2020)";
+
+	aliases {
+		serial0 = &serial0;
+	};
+
+	soc {
+		pwm@235044000 {
+			compatible = "apple,t8103-fpwm";
+			reg = <0x2 0x35044000 0x0 0x4000>;
+			clocks = <&clk24>;
+			#pwm-cells = <0>;
+		};
+	};
+
+	chosen {
+		#address-cells = <2>;
+		#size-cells = <2>;
+		ranges;
+
+		stdout-path = "serial0";
+
+		framebuffer0: framebuffer@0 {
+			compatible = "apple,simple-framebuffer", "simple-framebuffer";
+			reg = <0 0 0 0>; /* To be filled by loader */
+			/* Format properties will be added by loader */
+			status = "disabled";
+		};
+	};
+
+	memory@800000000 {
+		device_type = "memory";
+		reg = <0x8 0 0x2 0>; /* To be filled by loader */
+	};
+};
+
+&serial0 {
+	status = "okay";
+};

drivers/pwm/Kconfig

@@ -51,6 +51,18 @@ config PWM_AB8500
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-ab8500.
 
+config PWM_APPLE_M1
+	tristate "Apple M1 PWM support"
+	depends on ARCH_APPLE || COMPILE_TEST
+	depends on HAS_IOMEM && OF
+	help
+	  PWM driver for the FPWM found on Apple M1 SoCs. This is
+	  connected to the keyboard backlight on at least some
+	  MacBook Pros.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-apple-m1.
+
 config PWM_ATMEL
 	tristate "Atmel PWM support"
 	depends on ARCH_AT91 || COMPILE_TEST

drivers/pwm/Makefile

@@ -2,6 +2,7 @@
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
+obj-$(CONFIG_PWM_APPLE_M1)	+= pwm-apple-m1.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
 obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
 obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o

drivers/pwm/pwm-apple-m1.c

@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for Apple M1 FPWM
+ *
+ * Used for the keyboard backlight on at least some MacBook Pros.
+ *
+ * This driver requires a clock, which should provide the standard 24 MHz
+ * reference clock rate on M1 systems.
+ *
+ * The actual hardware appears to provide interrupt facilities and
+ * other unknown features, but those have not been reverse-engineered
+ * yet.
+ *
+ * Hardware documentation:
+ *
+ *   https://github.com/AsahiLinux/docs/wiki/HW:MacBook-Pro-keyboard-backlight-(FPWM0)
+ *
+ * Copyright (C) 2021 Pip Cet <pipcet@gmail.com>
+ *
+ * Based on pwm-twl-led.c, which is:
+ *
+ * Copyright (C) 2012 Texas Instruments
+ * Author: Peter Ujfalusi <peter.ujfalusi@ti.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/math64.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/slab.h>
+
+#define FPWM_CONTROL		0x00
+#define   CONTROL_UPDATE	   0x4239
+#define   CONTROL_DISABLE	   0
+#define FPWM_STATUS		0x08
+#define FPWM_COUNT_OFF		0x18
+#define FPWM_COUNT_ON		0x1c
+
+struct fpwm_chip {
+	struct pwm_chip chip;
+	void __iomem *reg;
+	struct clk *clk;
+	u64 rate;
+};
+
+static inline struct fpwm_chip *to_fpwm(struct pwm_chip *chip)
+{
+	return container_of(chip, struct fpwm_chip, chip);
+}
+
+static int fpwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+		       int duty_ns, int period_ns)
+{
+	struct fpwm_chip *fpwm = to_fpwm(chip);
+	long duty_ticks = div_u64(duty_ns * fpwm->rate, 1000000000);
+	long period_ticks = div_u64(period_ns * fpwm->rate, 1000000000);
+	long off_ticks = period_ticks - duty_ticks;
+
+	writel(duty_ticks, fpwm->reg + FPWM_COUNT_ON);
+	writel(off_ticks, fpwm->reg + FPWM_COUNT_OFF);
+	writel(CONTROL_UPDATE, fpwm->reg + FPWM_CONTROL);
+
+	return 0;
+}
+
+static int fpwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct fpwm_chip *fpwm = to_fpwm(chip);
+
+	writel(CONTROL_UPDATE, fpwm->reg + FPWM_CONTROL);
+
+	return 0;
+}
+
+static void fpwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct fpwm_chip *fpwm = to_fpwm(chip);
+
+	writel(CONTROL_DISABLE, fpwm->reg + FPWM_CONTROL);
+}
+
+static const struct pwm_ops fpwm_ops = {
+	.enable = fpwm_enable,
+	.disable = fpwm_disable,
+	.config = fpwm_config,
+	.owner = THIS_MODULE,
+};
+
+static int fpwm_probe(struct platform_device *pdev)
+{
+	struct fpwm_chip *fpwm;
+	struct resource *res;
+	int ret;
+
+	fpwm = devm_kzalloc(&pdev->dev, sizeof(*fpwm), GFP_KERNEL);
+	if (!fpwm)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+
+	fpwm->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(fpwm->clk))
+		return PTR_ERR(fpwm->clk);
+
+	ret = clk_prepare_enable(fpwm->clk);
+	if (ret)
+		return ret;
+
+	fpwm->rate = clk_get_rate(fpwm->clk);
+
+	fpwm->reg = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(fpwm->reg)) {
+		clk_disable_unprepare(fpwm->clk);
+		return PTR_ERR(fpwm->reg);
+	}
+
+	fpwm->chip.ops = &fpwm_ops;
+	fpwm->chip.npwm = 1;
+	fpwm->chip.dev = &pdev->dev;
+	fpwm->chip.base = -1;
+
+	ret = devm_pwmchip_add(&pdev->dev, &fpwm->chip);
+	if (ret < 0) {
+		clk_disable_unprepare(fpwm->clk);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, fpwm);
+
+	return 0;
+}
+
+static int fpwm_remove(struct platform_device *pdev)
+{
+	struct fpwm_chip *fpwm = platform_get_drvdata(pdev);
+
+	clk_disable_unprepare(fpwm->clk);
+
+	return 0;
+}
+
+static const struct of_device_id fpwm_of_match[] = {
+	{ .compatible = "apple,t8103-fpwm" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, fpwm_of_match);
+
+static struct platform_driver fpwm_driver = {
+	.driver = {
+		.name = "apple-m1-fpwm",
+		.of_match_table = of_match_ptr(fpwm_of_match),
+	},
+	.probe = fpwm_probe,
+	.remove = fpwm_remove,
+};
+module_platform_driver(fpwm_driver);
+
+MODULE_AUTHOR("Pip Cet <pipcet@gmail.com>");
+MODULE_DESCRIPTION("PWM driver for Apple M1 FPWM");
+MODULE_LICENSE("GPL");