did something

vendor/periph.io/x/host/v3/allwinner/pwm.go

@@ -0,0 +1,197 @@
+// Copyright 2016 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package allwinner
+
+import (
+	"fmt"
+	"strings"
+	"time"
+)
+
+const pwmClock = 24000000
+const pwmMaxPeriod = 0x10000
+
+// prescalers is the value for pwm0Prescale*
+var prescalers = []struct {
+	freq   uint32
+	scaler pwmPrescale
+}{
+	// Base frequency (min freq is half that) / PWM clock at pwmMaxPeriod
+	{pwmClock, pwmPrescale1},             //  24MHz / 366Hz
+	{pwmClock / 120, pwmPrescale120},     // 200kHz / 3Hz
+	{pwmClock / 180, pwmPrescale180},     // 133kHz / 2Hz
+	{pwmClock / 240, pwmPrescale240},     // 100kHz / 1.5Hz
+	{pwmClock / 360, pwmPrescale360},     //  66kHz / 1.01Hz
+	{pwmClock / 480, pwmPrescale480},     //  50kHz / 0.7Hz
+	{pwmClock / 12000, pwmPrescale12000}, //   2kHz
+	{pwmClock / 24000, pwmPrescale24000}, //   1kHz
+	{pwmClock / 36000, pwmPrescale36000}, // 666 Hz
+	{pwmClock / 48000, pwmPrescale48000}, // 500 Hz
+	{pwmClock / 72000, pwmPrescale72000}, // 333 Hz / 0.005Hz
+}
+
+const (
+	// 31:29 reserved
+	pwmBusy pwmCtl = 1 << 28 // PWM0_RDY
+	// 27:10 reserved (used for pwm1)
+	pwm0Mask       pwmCtl = (1 << 10) - 1
+	pwm0Bypass     pwmCtl = 1 << 9 // PWM0_BYPASS (marked as unused on some drivers?)
+	pwm0PulseStart pwmCtl = 1 << 8 // PWM_CH0_PUL_START
+	pwm0ModePulse  pwmCtl = 1 << 7 // PWM_CHANNEL0_MODE
+	pwm0SCLK       pwmCtl = 1 << 6 // SCLK_CH0_GATING
+	pwm0Polarity   pwmCtl = 1 << 5 // PWM_CH0_ACT_STA
+	pwm0Enable     pwmCtl = 1 << 4 // PWM_CH0_EN
+	// 3:0
+	pwm0PrescaleMask pwmCtl = pwmCtl(pwmPrescaleMask) // PWM_CH0_PRESCAL
+	pwm0Prescale120  pwmCtl = pwmCtl(pwmPrescale120)
+	pwm0Prescale180  pwmCtl = pwmCtl(pwmPrescale180)
+	pwm0Prescale240  pwmCtl = pwmCtl(pwmPrescale240)
+	pwm0Prescale360  pwmCtl = pwmCtl(pwmPrescale360)
+	pwm0Prescale480  pwmCtl = pwmCtl(pwmPrescale480)
+	// 5, 6, 7 reserved
+	pwm0Prescale12000 pwmCtl = pwmCtl(pwmPrescale12000)
+	pwm0Prescale24000 pwmCtl = pwmCtl(pwmPrescale24000)
+	pwm0Prescale36000 pwmCtl = pwmCtl(pwmPrescale36000)
+	pwm0Prescale48000 pwmCtl = pwmCtl(pwmPrescale48000)
+	pwm0Prescale72000 pwmCtl = pwmCtl(pwmPrescale72000)
+	// 13, 14 reserved
+	pwm0Prescale1 pwmCtl = pwmCtl(pwmPrescale1)
+)
+
+// A64: Pages 194-195.
+// R8: Pages 83-84.
+type pwmCtl uint32
+
+func (p pwmCtl) String() string {
+	var out []string
+	if p&pwmBusy != 0 {
+		out = append(out, "PWM0_RDY")
+		p &^= pwmBusy
+	}
+	if p&pwm0Bypass != 0 {
+		out = append(out, "PWM0_BYPASS")
+		p &^= pwm0Bypass
+	}
+	if p&pwm0PulseStart != 0 {
+		out = append(out, "PWM0_CH0_PUL_START")
+		p &^= pwm0PulseStart
+	}
+	if p&pwm0ModePulse != 0 {
+		out = append(out, "PWM0_CHANNEL0_MODE")
+		p &^= pwm0ModePulse
+	}
+	if p&pwm0SCLK != 0 {
+		out = append(out, "SCLK_CH0_GATING")
+		p &^= pwm0SCLK
+	}
+	if p&pwm0Polarity != 0 {
+		out = append(out, "PWM_CH0_ACT_STA")
+		p &^= pwm0Polarity
+	}
+	if p&pwm0Enable != 0 {
+		out = append(out, "PWM_CH0_EN")
+		p &^= pwm0Enable
+	}
+	out = append(out, pwmPrescale(p&pwm0PrescaleMask).String())
+	p &^= pwm0PrescaleMask
+	if p != 0 {
+		out = append(out, fmt.Sprintf("Unknown(0x%08X)", uint32(p)))
+	}
+	return strings.Join(out, "|")
+}
+
+const (
+	pwmPrescaleMask pwmPrescale = 0xF
+	pwmPrescale120  pwmPrescale = 0
+	pwmPrescale180  pwmPrescale = 1
+	pwmPrescale240  pwmPrescale = 2
+	pwmPrescale360  pwmPrescale = 3
+	pwmPrescale480  pwmPrescale = 4
+	// 5, 6, 7 reserved
+	pwmPrescale12000 pwmPrescale = 8
+	pwmPrescale24000 pwmPrescale = 9
+	pwmPrescale36000 pwmPrescale = 10
+	pwmPrescale48000 pwmPrescale = 11
+	pwmPrescale72000 pwmPrescale = 12
+	// 13, 14 reserved
+	pwmPrescale1 pwmPrescale = 15
+)
+
+type pwmPrescale uint32
+
+func (p pwmPrescale) String() string {
+	switch p {
+	case pwmPrescale120:
+		return "/120"
+	case pwmPrescale180:
+		return "/180"
+	case pwmPrescale240:
+		return "/240"
+	case pwmPrescale360:
+		return "/360"
+	case pwmPrescale480:
+		return "/480"
+	case pwmPrescale12000:
+		return "/12k"
+	case pwmPrescale24000:
+		return "/24k"
+	case pwmPrescale36000:
+		return "/36k"
+	case pwmPrescale48000:
+		return "/48k"
+	case pwmPrescale72000:
+		return "/72k"
+	case pwmPrescale1:
+		return "/1"
+	default:
+		return fmt.Sprintf("InvalidScalar(%d)", p&pwmPrescaleMask)
+	}
+}
+
+// A64: Page 195.
+// R8: Page 84
+type pwmPeriod uint32
+
+func (p pwmPeriod) String() string {
+	return fmt.Sprintf("%d/%d", p&0xFFFF, uint32((p>>16)&0xFFFF)+1)
+}
+
+func toPeriod(total uint32, active uint16) pwmPeriod {
+	if total > pwmMaxPeriod {
+		total = pwmMaxPeriod
+	}
+	return pwmPeriod(total-1)<<16 | pwmPeriod(active)
+}
+
+// getBestPrescale finds the best prescaler.
+//
+// Cycles must be between 2 and 0x10000/2.
+func getBestPrescale(period time.Duration) pwmPrescale {
+	// TODO(maruel): Rewrite this function, it is incorrect.
+	for _, v := range prescalers {
+		p := time.Second / time.Duration(v.freq)
+		smallest := (period / pwmMaxPeriod)
+		largest := (period / 2)
+		if p > smallest && p < largest {
+			return v.scaler
+		}
+	}
+	// Period is longer than 196s.
+	return pwmPrescale72000
+}
+
+// pwmMap represents the PWM memory mapped CPU registers.
+//
+// The base frequency is 24Mhz.
+//
+// TODO(maruel): Some CPU have 2 PWMs.
+type pwmMap struct {
+	ctl    pwmCtl    // PWM_CTRL_REG
+	period pwmPeriod // PWM_CH0_PERIOD
+}
+
+func (p *pwmMap) String() string {
+	return fmt.Sprintf("pwmMap{%s, %v}", p.ctl, p.period)
+}