machine,targets: add minimal esp32c6 implementation

This adds a minimal esp32c6 implementation, currently only
supporting the examples/serial and examples/blinky1 programs.
It does correctly output the expected "Hello, World" via the
serial port, as well as blink the onboard LED.

In addition, it adds support for the PLIC based IRQ handling
as used on the ESP32C6 processor.

Some parts of this code are loosely based on PR #5252 and #5248

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

builder/build.go

@@ -1076,7 +1076,7 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 		if err != nil {
 			return result, err
 		}
-	case "esp32", "esp32-img", "esp32c3", "esp32s3", "esp8266":
+	case "esp32", "esp32-img", "esp32c3", "esp32s3", "esp32c6", "esp8266":
 		// Special format for the ESP family of chips (parsed by the ROM
 		// bootloader).
 		result.Binary = filepath.Join(tmpdir, "main"+outext)

builder/builder_test.go

@@ -28,6 +28,7 @@ func TestClangAttributes(t *testing.T) {
 		"cortex-m4",
 		"cortex-m7",
 		"esp32c3",
+		"esp32c6",
 		"esp32s3",
 		"fe310",
 		"gameboy-advance",

builder/esp.go

@@ -100,12 +100,24 @@ func makeESPFirmwareImage(infile, outfile, format string) error {
 	chip_id := map[string]uint16{
 		"esp32":   0x0000,
 		"esp32c3": 0x0005,
+		"esp32c6": 0x000d,
 		"esp32s3": 0x0009,
 	}[chip]
 
+	// SPI flash speed/size byte (byte 3 of header):
+	//   Upper nibble = flash size, lower nibble = flash frequency.
+	//   The espflasher auto-detects and patches the flash size (upper nibble),
+	//   but the frequency (lower nibble) must be correct per chip.
+	spiSpeedSize := map[string]uint8{
+		"esp32":   0x1f, // 80MHz=0x0F, 2MB=0x10
+		"esp32c3": 0x1f, // 80MHz=0x0F, 2MB=0x10
+		"esp32c6": 0x10, // 80MHz=0x00, 2MB=0x10 (C6 uses different freq encoding)
+		"esp32s3": 0x1f, // 80MHz=0x0F, 2MB=0x10
+	}[chip]
+
 	// Image header.
 	switch chip {
-	case "esp32", "esp32c3", "esp32s3":
+	case "esp32", "esp32c3", "esp32s3", "esp32c6":
 		// Header format:
 		// https://github.com/espressif/esp-idf/blob/v4.3/components/bootloader_support/include/esp_app_format.h#L71
 		// Note: not adding a SHA256 hash as the binary is modified by
@@ -126,8 +138,8 @@ func makeESPFirmwareImage(infile, outfile, format string) error {
 		}{
 			magic:          0xE9,
 			segment_count:  byte(len(segments)),
-			spi_mode:       2,    // ESP_IMAGE_SPI_MODE_DIO
-			spi_speed_size: 0x1f, // ESP_IMAGE_SPI_SPEED_80M, ESP_IMAGE_FLASH_SIZE_2MB
+			spi_mode:       2, // ESP_IMAGE_SPI_MODE_DIO
+			spi_speed_size: spiSpeedSize,
 			entry_addr:     uint32(inf.Entry),
 			wp_pin:         0xEE, // disable WP pin
 			chip_id:        chip_id,