100 строки
2,6 КиБ
Go
100 строки
2,6 КиБ
Go
//go:build rp2040
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package machine
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import (
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"device/rp"
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"runtime/volatile"
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"unsafe"
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)
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type pll struct {
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cs volatile.Register32
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pwr volatile.Register32
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fbDivInt volatile.Register32
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prim volatile.Register32
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}
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var (
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pllSys = (*pll)(unsafe.Pointer(rp.PLL_SYS))
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pllUSB = (*pll)(unsafe.Pointer(rp.PLL_USB))
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)
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// init initializes pll (Sys or USB) given the following parameters.
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//
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// Input clock divider, refdiv.
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//
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// Requested output frequency from the VCO (voltage controlled oscillator), vcoFreq.
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//
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// Post Divider 1, postDiv1 with range 1-7 and be >= postDiv2.
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//
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// Post Divider 2, postDiv2 with range 1-7.
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func (pll *pll) init(refdiv, vcoFreq, postDiv1, postDiv2 uint32) {
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refFreq := xoscFreq / refdiv
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// What are we multiplying the reference clock by to get the vco freq
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// (The regs are called div, because you divide the vco output and compare it to the refclk)
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fbdiv := vcoFreq / (refFreq * MHz)
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// Check fbdiv range
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if !(fbdiv >= 16 && fbdiv <= 320) {
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panic("fbdiv should be in the range [16,320]")
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}
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// Check divider ranges
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if !((postDiv1 >= 1 && postDiv1 <= 7) && (postDiv2 >= 1 && postDiv2 <= 7)) {
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panic("postdiv1, postdiv1 should be in the range [1,7]")
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}
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// postDiv1 should be >= postDiv2
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// from appnote page 11
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// postdiv1 is designed to operate with a higher input frequency
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// than postdiv2
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if postDiv1 < postDiv2 {
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panic("postdiv1 should be greater than or equal to postdiv2")
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}
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// Check that reference frequency is no greater than vco / 16
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if refFreq > vcoFreq/16 {
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panic("reference frequency should not be greater than vco frequency divided by 16")
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}
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// div1 feeds into div2 so if div1 is 5 and div2 is 2 then you get a divide by 10
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pdiv := postDiv1<<rp.PLL_SYS_PRIM_POSTDIV1_Pos | postDiv2<<rp.PLL_SYS_PRIM_POSTDIV2_Pos
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if pll.cs.HasBits(rp.PLL_SYS_CS_LOCK) &&
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refdiv == pll.cs.Get()&rp.PLL_SYS_CS_REFDIV_Msk &&
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fbdiv == pll.fbDivInt.Get()&rp.PLL_SYS_FBDIV_INT_FBDIV_INT_Msk &&
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pdiv == pll.prim.Get()&(rp.PLL_SYS_PRIM_POSTDIV1_Msk&rp.PLL_SYS_PRIM_POSTDIV2_Msk) {
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// do not disrupt PLL that is already correctly configured and operating
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return
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}
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var pllRst uint32
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if pll == pllSys {
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pllRst = rp.RESETS_RESET_PLL_SYS
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} else {
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pllRst = rp.RESETS_RESET_PLL_USB
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}
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resetBlock(pllRst)
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unresetBlockWait(pllRst)
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// Load VCO-related dividers before starting VCO
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pll.cs.Set(refdiv)
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pll.fbDivInt.Set(fbdiv)
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// Turn on PLL
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pwr := uint32(rp.PLL_SYS_PWR_PD | rp.PLL_SYS_PWR_VCOPD)
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pll.pwr.ClearBits(pwr)
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// Wait for PLL to lock
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for !(pll.cs.HasBits(rp.PLL_SYS_CS_LOCK)) {
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}
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// Set up post dividers
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pll.prim.Set(pdiv)
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// Turn on post divider
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pll.pwr.ClearBits(rp.PLL_SYS_PWR_POSTDIVPD)
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}
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