Hello, I encountered a problem when using lpspi0 of imx8dxp as a slave controller in linux. The linux kernel build by Yocto, uses NXP i.MX Release Distro 5.4-zeus.
Connected to lpspi0 is an MCU spi controller pin, there is a 100R resistor between the two chip's spi pins connected. MCU spi controller as master, and sends messages periodically.
Device tree set as follow(only the relevant parts are listed):
pinctrl_lpspi0: lpspi0grp {
fsl,pins = <
IMX8QXP_SPI0_CS0_ADMA_SPI0_CS0 0x0600004c
IMX8QXP_SPI0_SCK_ADMA_SPI0_SCK 0x0600004c
IMX8QXP_SPI0_SDI_ADMA_SPI0_SDI 0x0600004c
IMX8QXP_SPI0_SDO_ADMA_SPI0_SDO 0x0600004c
>;
};
&lpspi0 {
#address-cells = <0>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_lpspi0>;
status = "okay";
/* as a slave mode */
spi-slave;
slave {
compatible = "rohm,dh2228fv";
}
};
Now I can find the correct device node in /dev directory, but in user space open /dev/spidev0.0 node calls kenel space read interface of spidev.c sync to read the message, the read result is all 0.
Observe each signal pin through an oscilloscope. When the user space program is not running, the signal of the MOSI pin is normal(about 3.3V). When the user space test program is run, the signal level of the MOSI pin is about 300mv, but MCU's MOSI pin is correct.( there is a 100R resistor between the two pins connected.)
The strange thing is that the CS and SCLK signals are correct regardless of whether the user space program is running or not.
I have tried to modify the pin configuration status of lpspi0 of imx8dxp, but it has no effect. Can any friends provide some solutions? Thank you very much !
