Help with LPSPI DMA in Synchronous Mode on RT1060EVKB

[ofirshe]

Hi @DerekSnell and @decsny,

After rebasing to align with the latest fix in the LPSPI driver Fix NXP LPSPI native chip select when using synchronous API with DMA, I’m seeing some unexpected behavior. For reference, I’m working with the RT1060EVKB board and have the following project configuration flags:

CONFIG_SPI=y
CONFIG_SPI_MCUX_LPSPI_DMA=y
CONFIG_SPI_ASYNC=n

I also updated the device tree to enable SPI transactions with DMA on the LPSPI peripheral:

&lpspi1 {
	status = "okay";
	/* DMA channels 0 and 1, muxed to LPSPI1 RX and TX */
	dmas = <&edma0 0 13>, <&edma0 1 14>;
	dma-names = "rx", "tx";
	pinctrl-0 = <&pinmux_lpspi1>;
	pinctrl-names = "default";
	transfer-delay = <500>;
	si5402: spi-dev-si5402@0 {
		compatible = "skyworks,si5402";
		status = "okay";
		spi-max-frequency = <1000000>;
		reg = <0>;
	};
};

Here’s the code I’m using for the transaction:

uint8_t tx_data[2] = { 0 };
uint8_t rx_data[4]  = { 0 };
uint16_t rx_len;
uint16_t tx_len;

tx_data[0] = 0xD0;
tx_len = 1;
rx_len = 3;
const struct spi_buf tx_buf = { .buf = tx_data, .len = tx_len };
const struct spi_buf rx_buf = { .buf = rx_data, .len = rx_len };
const struct spi_buf_set tx = { .buffers = &tx_buf, .count = 1 };
const struct spi_buf_set rx = { .buffers = &rx_buf, .count = 1 };
return spi_transceive_dt(&cfg->bus, &tx, &rx);

SPI configured mode: SPI_WORD_SET(8) | SPI_OP_MODE_MASTER | SPI_TRANSFER_MSB

From the waveform output , I noticed some issues:

1. The clock line remains high throughout the transaction, which is unexpected, as I’ve configured it for 1 MHz.
2. The MOSI channel does not display the expected data (0xD0).

Additionally, spi_transceive_dt returns -116, with an error log indicating <err> spi_mcux_lpspi: Timeout waiting for transfer complete.

When using the default LPSPI mode (non-DMA path) with the cs-gpios workaround in the DTS, I noticed this output from the digital analyzer:

Aside from the issue with the component on the MISO channel (which I'm troubleshooting separately), I'm unsure which of the two modes reflects the correct behavior for the code I shared above. In the DMA path, I observe a single transaction from the RT1060, whereas in the non-DMA path, I see two transactions.

Best regards,
Ofir.

[DerekSnell]

This is confirmed as an issue in the LPSPI driver, and this GitHub Issue will be used for tracking and further communication:
LPSPI driver with DMA does not work on NXP RT platform

[ofirshe]

Thanks @DerekSnell for the update.

Could you confirm the expected behavior of the LPSPI in non-DMA mode (assuming it is functioning correctly)? Should the RT1060 be issuing two separate transactions for the code I provided?

BR

[decsny]

non DMA mode chip select also doesn't work correctly, this is longstanding issue #16544

[ofirshe]

@decsny I mentioned that I'm using the cs-gpios workaround in the DTS to address the CS issue, but my question is specifically about the expected driver behavior for the code I attached. I’m uncertain why it's sending two transactions instead of one.

[DerekSnell]

Linking to your newer discussion #81264, as it seems to be a duplicate