Change set to produce a working blinky example

This is a minimum viable set of changes to tinygo, to get a blinky
example running. These should be broken into separate steps. The
changes are roughly:

* Remove the second stage bootloader because it has been replaced by the
  boot rom on the rp2040
* Add a minimum viable image desciptor to the binary, to allow the
  boot rom to recongize the binary as an application
* Disable the peripheral resets because the hardware works differently
  than the RP2040 (need to re-evaluate this)
* Skip PLL init because the boot rom should have enabled it. This should
  definitely be fixed and then re-enabled.
* When enabling a GPIO pin, disable the isolation latch

Only the GPIO hardware seems functional, the init routines should be
improved before continuing with other peripherals.

src/machine/machine_rp2.go

@@ -58,7 +58,7 @@ func machineInit() {
 	bits = ^uint32(initUnreset)
 	unresetBlockWait(bits)
 
-	clocks.init()
+//	clocks.init()
 
 	// Peripheral clocks should now all be running
 	unresetBlockWait(RESETS_RESET_Msk)

src/machine/machine_rp2350_resets.go

@@ -25,20 +25,20 @@ var resets = (*resetsType)(unsafe.Pointer(rp.RESETS))
 // resetBlock resets hardware blocks specified
 // by the bit pattern in bits.
 func resetBlock(bits uint32) {
-	resets.frceOff.Set(bits)
+//	resets.frceOff.Set(bits)
 }
 
 // unresetBlock brings hardware blocks specified by the
 // bit pattern in bits out of reset.
 func unresetBlock(bits uint32) {
-	resets.frceOn.Set(bits)
+//	resets.frceOn.Set(bits)
 }
 
 // unresetBlockWait brings specified hardware blocks
 // specified by the bit pattern in bits
 // out of reset and wait for completion.
 func unresetBlockWait(bits uint32) {
-	unresetBlock(bits)
-	for !resets.resetDone.HasBits(bits) {
-	}
+//	unresetBlock(bits)
+//	for !resets.resetDone.HasBits(bits) {
+//	}
 }

src/machine/machine_rp2_2350.go

@@ -7,6 +7,8 @@ import (
 	"unsafe"
 )
 
+var DefaultUART = UART0
+
 const (
 	LED             = GPIO25
 	_NUMBANK0_GPIOS = 48

src/machine/machine_rp2_gpio.go

@@ -126,7 +126,7 @@ func (p Pin) setSchmitt(trigger bool) {
 func (p Pin) setFunc(fn pinFunc) {
 	// Set input enable, Clear output disable
 	p.padCtrl().ReplaceBits(rp.PADS_BANK0_GPIO0_IE,
-		rp.PADS_BANK0_GPIO0_IE_Msk|rp.PADS_BANK0_GPIO0_OD_Msk, 0)
+		rp.PADS_BANK0_GPIO0_IE_Msk|rp.PADS_BANK0_GPIO0_OD_Msk|rp.PADS_BANK0_GPIO0_ISO_Msk, 0)
 
 	// Zero all fields apart from fsel; we want this IO to do what the peripheral tells it.
 	// This doesn't affect e.g. pullup/pulldown, as these are in pad controls.
@@ -136,7 +136,9 @@ func (p Pin) setFunc(fn pinFunc) {
 // init initializes the gpio pin
 func (p Pin) init() {
 	mask := uint32(1) << p
+
 	rp.SIO.GPIO_OE_CLR.Set(mask)
+
 	p.clr()
 }
 

targets/arm.ld

@@ -9,6 +9,7 @@ SECTIONS
     .text :
     {
         KEEP(*(.isr_vector))
+        KEEP(*(.embedded_block))
         *(.text)
         *(.text.*)
         *(.rodata)

targets/embedded_block.S

@@ -0,0 +1,11 @@
+// Inspired by embedded_start_block.inc.S and embedded_end_block.inc.S
+// Minimum viable block image from datasheet section 5.9.5.1, "Minimum Arm IMAGE_DEF"
+.section .embedded_block, "a"
+.p2align 2
+embedded_block:
+.word 0xffffded3
+.word 0x10210142
+.word 0x000001ff
+.word 0x00000000
+.word 0xab123579
+embedded_block_end:

targets/pico2.json

@@ -3,8 +3,7 @@
         "rp2350"
     ],
     "build-tags": ["pico2"],
-    "linkerscript": "targets/pico2.ld",
+    "linkerscript": "targets/rp2350.ld",
     "extra-files": [
-        "targets/pico_boot_stage2.S"
     ]
 }

targets/rp2350.json

@@ -8,9 +8,10 @@
     "msd-firmware-name": "firmware.uf2",
     "binary-format": "uf2",
     "uf2-family-id": "0xe48bff59","comment":"See page 393 of RP2350 datasheet: RP2350 Arm Secure image (i.e. one intended to be booted directly by the bootrom)",
-    "rp2040-boot-patch": true,
     "extra-files": [
-        "targets/rp2350_boot2_generic03h.S"
+        "src/device/rp/rp2350.s",
+        "targets/rp2350_boot2_generic03h.S",
+        "targets/embedded_block.S"
     ],
     "linkerscript": "targets/rp2350.ld",
     "openocd-interface": "picoprobe",

targets/rp2350.ld

@@ -10,30 +10,16 @@ MEMORY
        i.e: Separate stacks for core0 and core1. */
     SRAM4 : ORIGIN = 0x20080000, LENGTH = 4k
     SRAM5 : ORIGIN = 0x20081000, LENGTH = 4k
-    /* Reserve exactly 256 bytes at start of flash for second stage bootloader */
-    BOOT2_TEXT (rx) : ORIGIN = 0x10000000, LENGTH = 256
-    FLASH_TEXT (rx) : ORIGIN = 0x10000000 + 256, LENGTH = 2048k - 256
+    FLASH_TEXT (rx) : ORIGIN = 0x10000000, LENGTH = 2048k
+
+
     RAM (rwx)       : ORIGIN = 0x20000000, LENGTH = 512k
 }
 
 _stack_size = 2K;
 
 SECTIONS
 {
-    /* Second stage bootloader is prepended to the image. It must be 256 bytes
-       and checksummed.  The gap to the checksum is zero-padded.
-    */
-    .boot2 : {
-        __boot2_start__ = .;
-        KEEP (*(.boot2));
-
-        /* Explicitly allocate space for CRC32 checksum at end of second stage
-           bootloader
-        */
-        . = __boot2_start__ + 256 - 4;
-        LONG(0)
-    } > BOOT2_TEXT = 0x0
-
     /* The second stage will always enter the image at the start of .text.
        The debugger will use the ELF entry point, which is the _entry_point
        symbol if present, otherwise defaults to start of .text.