RP2350: SPI with DMA seems not working

[advancedlogic]

First of all, thanks for the amazing effort to develop TinyGo.
I am creating a library to experiment with the Geeek Pico Breadboard https://github.com/geeekpi/pico_breadboard_kit using the RP PICO 2 (RP2350).

• NeoPixel: OK
• Joystick: OK
• Leds: OK
• Buzzer (Speaker): KO, PWM seems not yet available for RP PICO 2
• Display (ST7796U): OK but without DMA
• Touch: Not implemented yet

I was able to modify the driver ST7789 to work with the ST7796U (480x320) but if I try to use the method Tx(w,r []byte) with more than 1 byte, the PICO 2 freezes during the initialization process and I did not find a way to understand why. Everything works if I send each byte using Transfer (but it's slow for a decent refresh rate). - https://github.com/tinygo-org/tinygo/blob/release/src/machine/machine_rp2_spi.go

I also tried with an ST7789 using the driver available https://github.com/tinygo-org/drivers/tree/release/st7789, with the RP PICO 2 and it freezes during the initialization process.

It seems related to the DMA access. In the RP2350 Datasheet it seems that for payloads less than 250MB it should be retro-compatible with RP2040 but the DMA SPI addresses seem different. I maybe wrong (I am not an expert in microcontrollers)

[advancedlogic]

I don't think the behavior is supposed to be this one, but I managed to make it work, transferring 4 Bytes at the time:

func (d *DeviceOf[T]) sendCommand(command uint8) error {
	d.dcPin.Low()
	d.csPin.Low()
	err := d.bus.Tx([]byte{command}, nil)
	d.csPin.High()
	return err
}

func (d *DeviceOf[T]) sendData(data []byte) error {
	d.dcPin.High()
	d.csPin.Low()
	for i := 0; i < len(data); i += 4 {
		end := i + 4
		if end > len(data) {
			end = len(data)
		}
		if err := d.bus.Tx(data[i:end], nil); err != nil {
			return err
		}
	}
	d.csPin.High()
	return nil
}