NXP FlexComm LPSPI Problems - FRDM-MCXN947

[ECleverito]

I am looking to use the LPSPI modules available on the MCXN947's FlexComms, but I am unable to see any activity from the controllers when I attempt to write to them. I initially desired to use the LPSPI on FC6 in order to use a Mikroe Clickboard on the MikroBus slot. I added entries for this FlexComm module to my existing overlay:

/ {
	aliases{
		mikroe-slot-i2c = &flexcomm3_lpi2c3;
		mikroe-slot-spi = &flexcomm6_lpspi6;
		j2-spi = &flexcomm1_lpspi1;
	};
};

&pinctrl {

	pinmux_flexcomm3_lpi2c: pinmux_flexcomm3_lpi2c {
		group0 {
			pinmux = <FC3_P0_PIO1_0>,
				<FC3_P1_PIO1_1>;
			slew-rate = "fast";
			drive-strength = "low";
			input-enable;
			bias-pull-up;
			drive-open-drain;
		};
	};

	pinmux_flexcomm6_lpspi: pinmux_flexcomm6_lpspi {
		group0 {
			pinmux = <FC6_P1_PIO3_21>,
				<FC6_P2_PIO3_22>,
				<FC6_P0_PIO3_20>;
			slew-rate = "fast";
			drive-strength = "low";
			input-enable;
		};
	};

};

&peripheral
{
    flexcomm3: flexcomm@95000 {
        status = "okay";
        flexcomm3_lpi2c3: lpi2c@95800 {
            status = "okay";    
            pinctrl-0 = <&pinmux_flexcomm3_lpi2c>;
            pinctrl-names = "default";
			clock-frequency = <I2C_BITRATE_STANDARD>;
        };        
    };
    flexcomm6: flexcomm@b6000 {
        status = "okay";
        flexcomm6_lpspi6: spi@b6000 {
            status = "okay";    
	    cs-gpios = <&gpio3 23 GPIO_ACTIVE_LOW>;
            pinctrl-0 = <&pinmux_flexcomm6_lpspi>;
            pinctrl-names = "default";
			transfer-delay = <1000>;
			eInkDisp: eInkDisp@0 {
				compatible = "vnd,spi-device";
				status = "okay";
				reg = <0>;
				spi-max-frequency = <100000>;
				label = "eInkDisp";
			};
           };
    };
};
&flexcomm3 {
	status = "okay";
};

&flexcomm3_lpi2c3 {
	status = "okay";
};

&flexcomm6 {
	status = "okay";
};

&flexcomm6_lpspi6 {
	status = "okay";
};

I mainly followed the example in the frdm_mcxn947_mcxn947_cpu0.dtsi overlay, as support for LPSPI was added for this board earlier in this commit. The resulting zephyr.dts shows flexomm6_lpspi as "okay" and I am able to retrieve a node ID with the DEVICE_DT_GET() macro and a spi_dt_spec using SPI_DT_SPEC_GET(). To test writing to this device with the zephyr APIs, I have tried manually creating the spi_dt_spec with the node_id:

#define SPI_DEVICE_NODE DT_ALIAS(mikroe_slot_spi)

const struct device *const spi_dev = DEVICE_DT_GET(SPI_DEVICE_NODE);

struct spi_config my_spi_cfg;

int init_spi_device()
{
	my_spi_cfg.frequency = 100000;
	my_spi_cfg.operation = PERVASIVE_E_INK_SPI_OPS_CFG;
	my_spi_cfg.slave = 0;

	if (!device_is_ready(spi_dev))
    {
		LOG_ERR("SPI device not ready.");
		return -1;
	}    

	char str_to_send[] = "Hello World";
	struct spi_buf hello_world_buf;
	hello_world_buf.buf = str_to_send;
	hello_world_buf.len = sizeof(str_to_send);

	struct spi_buf_set hello_world_buf_set;
	hello_world_buf_set.buffers = &hello_world_buf;
	hello_world_buf_set.count = 1;

	int ret = spi_write(spi_dev, &my_spi_cfg, &hello_world_buf_set);
	if(ret < 0)
    {
		LOG_ERR("spi_write error: %d", ret);
		return -1;
	}    	

    return 0;
}

This however, results in the following runtime error:

[00:00:00.005,000] <err> spi_mcux_lpspi: Transfer could not start on spi@b6000: 4
[00:00:00.013,000] <err> e_ink_log: spi_write error: -22

This error is returned at the end of spi_mcux_transfer_next_packet() in the spi_mcux_lpspi.c driver file:

	status = LPSPI_MasterTransferNonBlocking(base, &data->handle, &transfer);
	if (status != kStatus_Success) {
		LOG_ERR("Transfer could not start on %s: %d", dev->name, status);
		return status == kStatus_LPSPI_Busy ? -EBUSY : -EINVAL;
	}

I find it strange that the ...NonBlocking() API is called since I do not have CONFIG_SPI_ASYNC set. Overall, I would like to know if there is anything glaring missing from my overlay device definitions. I have played with the "spi-max-frequency" property by lowering it as well as the spi_config frequency, as I have seen that this caused some troubles in other threads discussing LPSPI. Even at 100 kHz, I am still not seeing successful writes or any activity on the bus. I have tried this with LPSPI1 on FC1 as well, the default lpspi in the overlay, to no avail.

Additionally, here are the contents of my application-specific configuration file:

#Configurer Zephyr drivers
CONFIG_GPIO=y

CONFIG_SERIAL=y
CONFIG_UART_INTERRUPT_DRIVEN=y

CONFIG_I2C=y
CONFIG_SPI=y

CONFIG_CONSOLE=y
CONFIG_UART_CONSOLE=y

CONFIG_LOG=y

# Use level below to change level of log messages to filter:
# (O=OFF; 1=ERR; 2=WRN; 3=INF; 4=DBG)
CONFIG_LOG_MAX_LEVEL=1
CONFIG_LOG_DEFAULT_LEVEL=4

CONFIG_STDOUT_CONSOLE=y
CONFIG_LOG_BACKEND_UART=y
CONFIG_LOG_MODE_IMMEDIATE=y

I would like to add that I did learn that clock gating is performed in the board.c, which I have already modified to send the clock to FlexComm6:

#if DT_NODE_HAS_STATUS_OKAY(DT_NODELABEL(flexcomm6))
	CLOCK_SetClkDiv(kCLOCK_DivFlexcom6Clk, 1u);
	CLOCK_AttachClk(kFRO12M_to_FLEXCOMM6);
#endif

What would be the proper way to send this clock without modifying the zephyr source?

[ECleverito]

Tagging for visibility:

@mmahadevan108 I noticed you added the definition of flexcomm1_lpspi1 to the FRDM-MCXN947's base overlay. Were you able to utilize the LPSPI successfully?

@danieldegrasse I sent you an email earlier and you suggested moving this discussion to GitHub

@DerekSnell I have seen you commenting on related threads where you mentioned that work has been underway on the spi_mcux_plspi driver