# --- T2-COPYRIGHT-BEGIN ---
# t2/package/*/linux/riscv-unmatched-fans.patch
# Copyright (C) 2021 - 2025 The T2 SDE Project
# SPDX-License-Identifier: GPL-2.0 or patched project license
# --- T2-COPYRIGHT-END ---

Let's implement some minimal viable HiFive Unmatched PWM fan control.

Signed-off-by: René Rebe <rene@exactcode.com>

--- ./arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts.vanilla	2024-04-01 18:58:55.930393689 +0200
+++ ./arch/riscv/boot/dts/sifive/hifive-unmatched-a00.dts	2024-04-01 20:32:34.682852300 +0200
@@ -47,6 +47,18 @@
 		gpios = <&gpio 2 GPIO_ACTIVE_LOW>;
 	};
 
+	fan1 {
+		compatible = "pwm-fan";
+		pwms = <&pwm1 2 7812500 PWM_POLARITY_INVERTED>;
+		active-low;
+	};
+
+	fan2 {
+		compatible = "pwm-fan";
+		pwms = <&pwm1 3 7812500 PWM_POLARITY_INVERTED>;
+		active-low;
+	};
+
 	led-controller-1 {
 		compatible = "pwm-leds";
 
--- linux-6.13/drivers/hwmon/pwm-fan.c.vanilla	2025-02-03 11:42:43.909573585 +0100
+++ linux-6.13/drivers/hwmon/pwm-fan.c	2025-02-03 11:44:47.423592732 +0100
@@ -45,6 +45,7 @@
 	enum pwm_fan_enable_mode enable_mode;
 	bool regulator_enabled;
 	bool enabled;
+	bool active_low;
 
 	int tach_count;
 	struct pwm_fan_tach *tachs;

@@ -227,6 +227,9 @@
 		if (!ret && update) {
 			pwm = final_pwm;
 			state->duty_cycle = DIV_ROUND_UP(pwm * (period - 1), MAX_PWM);
+			if (ctx->active_low)
+				state->duty_cycle = state->period - state->duty_cycle;
+
 			usleep_range(ctx->pwm_usec_from_stopped,
 				     ctx->pwm_usec_from_stopped * 2);
 			ret = pwm_apply_might_sleep(ctx->pwm, state);
@@ -476,6 +480,7 @@
 {
 	struct thermal_cooling_device *cdev;
 	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
 	struct pwm_fan_ctx *ctx;
 	struct device *hwmon;
 	int ret;
@@ -526,6 +532,7 @@
 	}
 
 	ctx->enable_mode = pwm_disable_reg_enable;
+	ctx->active_low = of_property_read_bool(np, "active-low");
 
 	/*
 	 * Set duty cycle to maximum allowed and enable PWM output as well as