github.com/f-secure-foundry/tamago@v0.0.0-20220307101044-d73fcdd7f11b/soc/bcm2835/bcm2835.go (about)

     1  // BCM2835 SoC support
     2  // https://github.com/f-secure-foundry/tamago
     3  //
     4  // Copyright (c) the bcm2835 package authors
     5  //
     6  // Use of this source code is governed by the license
     7  // that can be found in the LICENSE file.
     8  
     9  // Package bcm2835 provides support to Go bare metal unikernels written using
    10  // the TamaGo framework on BCM2835/BCM2836 SoCs.
    11  //
    12  // This package is only meant to be used with `GOOS=tamago GOARCH=arm` as
    13  // supported by the TamaGo framework for bare metal Go on ARM SoCs, see
    14  // https://github.com/f-secure-foundry/tamago.
    15  package bcm2835
    16  
    17  import (
    18  	_ "unsafe"
    19  
    20  	"github.com/f-secure-foundry/tamago/arm"
    21  )
    22  
    23  // nanos - should be same value as arm/timer.go refFreq
    24  const refFreq int64 = 1000000000
    25  
    26  // DRAM_FLAG_NOCACHE disables caching by setting to high bits
    27  const DRAM_FLAG_NOCACHE = 0xC0000000
    28  
    29  // peripheralBase represents the (remapped) peripheral base address, it varies
    30  // by model and it is therefore initialized (see Init) by individual board
    31  // packages.
    32  var peripheralBase uint32
    33  
    34  // ARM processor instance
    35  var ARM = &arm.CPU{}
    36  
    37  //go:linkname ramStackOffset runtime.ramStackOffset
    38  var ramStackOffset uint32 = 0x100000 // 1 MB
    39  
    40  //go:linkname nanotime1 runtime.nanotime1
    41  func nanotime1() int64 {
    42  	return read_systimer() * ARM.TimerMultiplier + ARM.TimerOffset
    43  }
    44  
    45  // Init takes care of the lower level SoC initialization triggered early in
    46  // runtime setup.
    47  func Init(base uint32) {
    48  	peripheralBase = base
    49  
    50  	ARM.Init()
    51  	ARM.EnableVFP()
    52  
    53  	// required when booting in SDP mode
    54  	ARM.EnableSMP()
    55  
    56  	// MMU initialization is required to take advantage of data cache
    57  	ARM.InitMMU()
    58  	ARM.EnableCache()
    59  
    60  	ARM.TimerMultiplier = refFreq / SysTimerFreq
    61  	ARM.TimerFn = read_systimer
    62  
    63  	// initialize serial console
    64  	MiniUART.Init()
    65  }
    66  
    67  // PeripheralAddress returns the absolute address for a peripheral. The Pi
    68  // boards map 'bus addresses' to board specific base addresses but with
    69  // consistent layout otherwise.
    70  func PeripheralAddress(offset uint32) uint32 {
    71  	return peripheralBase + offset
    72  }