Rpi3 baremetal

rpi3/00_simple/.gitignore

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+kernel8.*
+.gdbinit
+*.o

rpi3/00_simple/Makefile

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+#
+# Simplest bootloader example (prints hello world on serial port, UART0, then echos what you type at it)
+#
+
+all: clean kernel8.elf
+
+# note the target is rpi3_bl in this directory
+kernel8.elf: simple.go rpi3_bl.o
+	tinygo build --target=rpi3_bl  -target 'rpi3_bl.json' -ldflags 'rpi3_bl.o' -o kernel8.elf .
+
+rpi3_bl.o: rpi3_bl.S
+	clang --target=aarch64-elf -c rpi3_bl.S
+
+clean:
+	rm kernel8.elf kernel8.img *.o >/dev/null 2>/dev/null || true

rpi3/00_simple/go.mod

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+module interrupts
+
+go 1.11
+
+require github.com/tinygo-org/tinygo v0.7.1 // indirect

rpi3/00_simple/go.sum

@@ -0,0 +1,16 @@
+github.com/blakesmith/ar v0.0.0-20150311145944-8bd4349a67f2 h1:oMCHnXa6CCCafdPDbMh/lWRhRByN0VFLvv+g+ayx1SI=
+github.com/blakesmith/ar v0.0.0-20150311145944-8bd4349a67f2/go.mod h1:PkYb9DJNAwrSvRx5DYA+gUcOIgTGVMNkfSCbZM8cWpI=
+github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/marcinbor85/gohex v0.0.0-20180128172054-7a43cd876e46 h1:wXG2bA8fO7Vv7lLk2PihFMTqmbT173Tje39oKzQ50Mo=
+github.com/marcinbor85/gohex v0.0.0-20180128172054-7a43cd876e46/go.mod h1:Pb6XcsXyropB9LNHhnqaknG/vEwYztLkQzVCHv8sQ3M=
+github.com/tinygo-org/tinygo v0.7.1 h1:DbKW4LglJLr9L3zykwFkUR/974mVwZEtnSeOzUsslRQ=
+github.com/tinygo-org/tinygo v0.7.1/go.mod h1:lw4bWjN/+Nm/9ypTo6BgAlYNLS9GrpP7Rw5g0bWAwew=
+golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/net v0.0.0-20190213061140-3a22650c66bd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/tools v0.0.0-20190227180812-8dcc6e70cdef h1:ymc9FeDom3RIEA3coKokSllBB1hRcMT0tZ1W3Jf9Ids=
+golang.org/x/tools v0.0.0-20190227180812-8dcc6e70cdef/go.mod h1:9Yl7xja0Znq3iFh3HoIrodX9oNMXvdceNzlUR8zjMvY=
+google.golang.org/appengine v1.4.0/go.mod h1:xpcJRLb0r/rnEns0DIKYYv+WjYCduHsrkT7/EB5XEv4=
+tinygo.org/x/go-llvm v0.0.0-20190224120431-7707ae5d1261 h1:rJS2Hga39YAnm7DE4qrPm6Dr/67EOojL0XPzvbEeBiw=
+tinygo.org/x/go-llvm v0.0.0-20190224120431-7707ae5d1261/go.mod h1:fv1F0BSNpxMfCL0zF3M4OPFbgYHnhtB6ST0HvUtu/LE=

rpi3/00_simple/rpi3_bl.S

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+.section ".text.boot_bl"
+
+//
+// The bootloader changes execution state for bootloaded code to EL2 if that is
+// needed. This is after execution switches to the bootloaded code, and it drops
+// to EL1 once the stack is setup ok.
+//
+
+// startup parameters are:
+// x0 - start address (also in PC)
+// x1 - stack ptr
+// x2 - heap ptr
+// x3 - unix time
+.global _start
+	//set the sp for el1, but we have to have the fp space so subtract 16 (two 64bit ptr)
+	sub x1,x1,#16
+	msr     sp_el1, x1
+
+
+	// enable CNTP for EL1
+	mrs     x27, cnthctl_el2
+	orr     x27, x27, #3
+	msr     cnthctl_el2, x27
+	msr     cntvoff_el2, xzr
+
+	// enable AArch64 in EL1
+	mov     x27, #(1 << 31)      // AArch64
+	orr     x27, x27, #(1 << 1)   // SWIO hardwired on Pi3
+	msr     hcr_el2, x27
+	mrs     x27, hcr_el2
+
+	// system control register
+	mov     x4, #0x0800
+	movk    x4, #0x30d0, lsl #16
+	msr     sctlr_el1, x4
+
+	//insert default vectors for core 0
+	ldr x27, =vectors
+	msr vbar_el1, x27
+
+	// change execution level to EL1
+	mov     x27, #0x3c5  //5! not 4! we have our own stack
+	msr     spsr_el2, x27
+	adr     x27, 1f
+	msr     elr_el2, x27
+	eret
+
+## getting the stack and fp in order, we subtracted 16 from x1 earlier in bootloader
+## note that we store 0 for the link and ret values because we are at the
+## bottom of the stack and want stack to correctly show in GDB and similar
+1:
+	# fp to bottom of frame
+	add x27, x1, #16
+	mov x29, x27
+
+	#shove values in based on top of stack
+	str xzr, [sp, #8]
+	str xzr, [sp, #16]
+
+	//sp points to top of stack (for Bootloaded code 0x30000 - 0x20)
+	//fp points to bottom (x29) (for Bootloaded code 0x30000 - 0x10)
+
+	//tell hardware that EL0 has own stack
+	//msr SPSel, #1
+
+	// jump to go code
+	bl      mainFromBootloader
+	// for failsafe, halt this core too
+	wfe

rpi3/00_simple/rpi3_bl.json

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+{
+	"inherits": ["rpi3"],
+	"linkerscript": "rpi3_bl.ld"
+}

rpi3/00_simple/rpi3_bl.ld

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+SECTIONS
+{
+. = 0x10000;
+.text : { KEEP(*(.text.boot_bl)) *(.text .text.* .gnu.linkonce.t*) }
+.rodata : { *(.rodata .rodata.* .gnu.linkonce.r*) }
+PROVIDE(_data = .);
+.data : { *(.data .data.* .gnu.linkonce.d*) }
+.bss (NOLOAD) : {
+		. = ALIGN(16);
+		__bss_start = .;
+		*(.bss .bss.*)
+		*(COMMON)
+		__bss_end = .;
+}
+_end = .;
+
+/DISCARD/ : { *(.comment) *(.gnu*) *(.note*) *(.eh_frame*) *(.text.boot)}
+}
+__bss_size = (__bss_end - __bss_start)>>3;

rpi3/00_simple/simple.go

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+package main
+
+import (
+	dev "device/rpi3"
+)
+
+func main() {
+	print("hello world!\nechoing what you type\n")
+	for {
+		c := dev.UART0Getc()
+		dev.UART0Send(c)
+	}
+}

rpi3/01_blinker/.gitignore

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+kernel8.*
+*.o

rpi3/01_blinker/Makefile

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+#
+# Use interrupts to blink the light on the RPI3.
+#
+
+all: clean kernel8.elf
+
+# note the target is rpi3_bl in this directory
+kernel8.elf: clean rpi3_bl.o
+	tinygo build --target=rpi3_bl.json -target 'rpi3_bl.json' -ldflags 'rpi3_bl.o' -o kernel8.elf .
+
+rpi3_bl.o: rpi3_bl.S
+	clang --target=aarch64-elf -c rpi3_bl.S
+
+clean:
+	rm kernel8.elf kernel8.img *.o >/dev/null 2>/dev/null || true

rpi3/01_blinker/blinker.go

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+package main
+
+import (
+	dev "device/rpi3"
+)
+
+var on = false
+var interval uint32
+
+// it's more than a little unclear that the values passed to this
+// interrupt handler are ever going to be useful
+func blinker(_ uint32, _ uint64) uint32 {
+	dev.LEDSet(on)
+	on = !on
+	print("set LED to ", on, "\n")
+	return interval
+}
+
+func main() {
+	hi, lo := dev.GetRPIID()
+	if hi == 0 && lo == 0 {
+		print("you are running on QEMU so you aren't going to see any lights blinking...\n")
+	}
+
+	freq := dev.CounterFreq() //getting my freq on
+	print("frequency per second is:")
+	dev.UART0Hex(freq) //this number is number of ticks/sec
+
+	//sets the timer for  N secs, where N is multiplier
+	interval = 1 * freq
+	dev.SetCounterTargetInterval(interval, blinker)
+	dev.Core0CounterToCore0Irq()
+	dev.EnableCounter()
+	dev.EnableTimerIRQ()
+	for {
+		dev.WaitForInterrupt()
+	}
+}

rpi3/01_blinker/rpi3_bl.S

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+.section ".text.boot_bl"
+
+//
+// The bootloader changes execution state for bootloaded code to EL2 if that is
+// needed. This is after execution switches to the bootloaded code, and it drops
+// to EL1 once the stack is setup ok.
+//
+
+// startup parameters are:
+// x0 - start address (also in PC)
+// x1 - stack ptr
+// x2 - heap ptr
+// x3 - unix time
+.global _start
+	//set the sp for el1, but we have to have the fp space so subtract 16 (two 64bit ptr)
+	sub x1,x1,#16
+	msr     sp_el1, x1
+
+
+	// enable CNTP for EL1
+	mrs     x27, cnthctl_el2
+	orr     x27, x27, #3
+	msr     cnthctl_el2, x27
+	msr     cntvoff_el2, xzr
+
+	// enable AArch64 in EL1
+	mov     x27, #(1 << 31)      // AArch64
+	orr     x27, x27, #(1 << 1)   // SWIO hardwired on Pi3
+	msr     hcr_el2, x27
+	mrs     x27, hcr_el2
+
+	// system control register
+	mov     x4, #0x0800
+	movk    x4, #0x30d0, lsl #16
+	msr     sctlr_el1, x4
+
+	//insert default vectors for core 0
+	ldr x27, =vectors
+	msr vbar_el1, x27
+
+	// change execution level to EL1
+	mov     x27, #0x3c5  //5! not 4! we have our own stack
+	msr     spsr_el2, x27
+	adr     x27, 1f
+	msr     elr_el2, x27
+	eret
+
+## getting the stack and fp in order, we subtracted 16 from x1 earlier in bootloader
+## note that we store 0 for the link and ret values because we are at the
+## bottom of the stack and want stack to correctly show in GDB and similar
+1:
+	# fp to bottom of frame
+	add x27, x1, #16
+	mov x29, x27
+
+	#shove values in based on top of stack
+	str xzr, [sp, #8]
+	str xzr, [sp, #16]
+
+	//sp points to top of stack (for Bootloaded code 0x30000 - 0x20)
+	//fp points to bottom (x29) (for Bootloaded code 0x30000 - 0x10)
+
+	//tell hardware that EL0 has own stack
+	//msr SPSel, #1
+
+	// jump to go code
+	bl      mainFromBootloader
+	// for failsafe, halt this core too
+	wfe

rpi3/01_blinker/rpi3_bl.json

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+{
+	"inherits": ["rpi3"],
+	"linkerscript": "rpi3_bl.ld"
+}

rpi3/01_blinker/rpi3_bl.ld

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+SECTIONS
+{
+. = 0x10000;
+.text : { KEEP(*(.text.boot_bl)) *(.text .text.* .gnu.linkonce.t*) }
+.rodata : { *(.rodata .rodata.* .gnu.linkonce.r*) }
+PROVIDE(_data = .);
+.data : { *(.data .data.* .gnu.linkonce.d*) }
+.bss (NOLOAD) : {
+		. = ALIGN(16);
+		__bss_start = .;
+		*(.bss .bss.*)
+		*(COMMON)
+		__bss_end = .;
+}
+_end = .;
+
+/DISCARD/ : { *(.comment) *(.gnu*) *(.note*) *(.eh_frame*) *(.text.boot)}
+}
+__bss_size = (__bss_end - __bss_start)>>3;

rpi3/02_delays/.gitignore

@@ -0,0 +1,2 @@
+kernel8.*
+*.o

rpi3/02_delays/Makefile

@@ -0,0 +1,15 @@
+#
+# Use the bootloader to test our delays.
+#
+
+all: clean kernel8.elf
+
+# note the target is rpi3_bl in this directory
+kernel8.elf: rpi3_bl.o
+	tinygo build -target 'rpi3_bl.json' -ldflags 'rpi3_bl.o' -no-debug  -o kernel8.elf .
+
+rpi3_bl.o: rpi3_bl.S
+	clang --target=aarch64-elf -c rpi3_bl.S
+
+clean:
+	rm kernel8.elf kernel8.img *.o >/dev/null 2>/dev/null || true

rpi3/02_delays/delays.go

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+package main
+
+import (
+	dev "device/rpi3"
+)
+
+var interval uint32
+
+// not sure how useful the current value is, but the virtual timer should
+// have increased by exactly interval (or very close to it)
+// return the amount of time to wait for the next call to this callback
+// return 0 if you don't want it anymore
+func myHandler(current uint32, virtualTimer uint64) uint32 {
+	print("my handler, current: ")
+	dev.UART0Hex(current)
+	print("my handler, virtual timer: ")
+	dev.UART0Hex64(virtualTimer)
+	return interval
+}
+
+func main() {
+	dev.UART0TimeDateString(dev.Now())
+	print("\n")
+	testDelays()
+	// dev.BComTimerInit(interval)
+	// dev.EnableInterruptController()
+	// dev.EnableTimerIRQ()
+	//
+	// for {
+	// 	dev.WaitForInterrupt()
+	// }
+	dev.Abort()
+}
+
+func testDelays() {
+	print("Waiting 3000000 CPU cycles (ARM CPU): ")
+	dev.WaitCycles(3000000)
+	print("OK\n")
+
+	print("Waiting 3000000 microsec (ARM CPU): ")
+	dev.WaitMuSec(3000000)
+	print("OK\n")
+
+	print("Waiting 3000000 microsec (BCM System Timer): ")
+	if dev.SysTimer() == 0 {
+		print("Not available\n")
+	} else {
+		dev.WaitMuSecST(3000000)
+		print("OK\n")
+	}
+}