targets: add implementation for Tillitis TKey device (#4631)

* initial implementation for Tillitis TKey device
* add UART implementation for TKey
* add Pin interface implementation for TKey touch sensor
* add RNG interface implementation for TKey
* add helpful machine package functions to return identifiers such as name and version for TKey
* use built-in timer for sleep timing on TKey
* modify UART implementation for TKey to implement Serialer interface
* implement BLAKE2s ROM function call for TKey device
* handle abort by triggering TKey device fault using illegal instruction to halt CPU
* simplify TKey implementation by inheriting from existing riscv32 target
* return error for trying to configure invalid baudrates on UART
* add tkey to builder test
* be very specific for features passed to LLVM for specific config in use for TKey
* handle feedback items from TKey device code review

Signed-off-by: deadprogram <ron@hybridgroup.com>

src/machine/machine_tkey_rom.go

@@ -0,0 +1,59 @@
+//go:build tkey
+
+package machine
+
+/*
+	#define TK1_MMIO_TK1_BLAKE2S 0xff000040
+
+	typedef unsigned char uint8_t;
+	typedef unsigned long uint32_t;
+	typedef unsigned long size_t;
+
+	// blake2s state context
+	typedef struct {
+		uint8_t b[64]; // input buffer
+		uint32_t h[8]; // chained state
+		uint32_t t[2]; // total number of bytes
+		size_t c;      // pointer for b[]
+		size_t outlen; // digest size
+	} blake2s_ctx;
+
+	typedef int (*fw_blake2s_p)(void *out, unsigned long outlen, const void *key,
+		unsigned long keylen, const void *in,
+		unsigned long inlen, blake2s_ctx *ctx);
+
+	int blake2s(void *out, unsigned long outlen, const void *key, unsigned long keylen, const void *in, unsigned long inlen)
+	{
+		fw_blake2s_p const fw_blake2s =
+	    	(fw_blake2s_p) * (volatile uint32_t *)TK1_MMIO_TK1_BLAKE2S;
+		blake2s_ctx ctx;
+
+		return fw_blake2s(out, outlen, key, keylen, in, inlen, &ctx);
+	}
+*/
+import "C"
+import (
+	"errors"
+	"unsafe"
+)
+
+var (
+	ErrBLAKE2sInvalid = errors.New("invalid params for call to BLAKE2s")
+	ErrBLAKE2sFailed  = errors.New("call to BLAKE2s failed")
+)
+
+func BLAKE2s(output []byte, key []byte, input []byte) error {
+	if len(output) == 0 || len(input) == 0 {
+		return ErrBLAKE2sInvalid
+	}
+
+	op := unsafe.Pointer(&output[0])
+	kp := unsafe.Pointer(&key[0])
+	ip := unsafe.Pointer(&input[0])
+
+	if res := C.blake2s(op, C.size_t(len(output)), kp, C.size_t(len(key)), ip, C.size_t(len(input))); res != 0 {
+		return ErrBLAKE2sFailed
+	}
+
+	return nil
+}