[FAQ] CCS/TDA4VM: How to use SPI/SPI_DEV on TDA4/J721E?

Please find the answers in order:

1) How to enable SPI instances of TDA4VM?

For example lets us take main domain spi6 instance. To enable spi6 we need to add the device tree node & the corresponding pinmux node.

diff --git a/arch/arm64/boot/dts/ti/k3-j721e-common-proc-board.dts b/arch/arm64/boot/dts/ti/k3-j721e-common-proc-board.dts
index 6788a3611..77b845354 100644
--- a/arch/arm64/boot/dts/ti/k3-j721e-common-proc-board.dts
+++ b/arch/arm64/boot/dts/ti/k3-j721e-common-proc-board.dts
@@ -170,6 +170,18 @@
 		>;
 	};
 
+	spi6_pins_default: spi6_pins_default {
+		pinctrl-single,pins = <
+			J721E_IOPAD(0x9c, PIN_INPUT, 4) /* (AC22) PRG1_PRU1_GPO17.SPI6_CLK */
+			J721E_IOPAD(0x74, PIN_INPUT, 4) /* (AC21) PRG1_PRU1_GPO7.SPI6_CS0 */
+			J721E_IOPAD(0x28, PIN_INPUT, 4) /* (AG20) PRG1_PRU0_GPO9.SPI6_CS1 */
+			J721E_IOPAD(0x2c, PIN_INPUT, 4) /* (AD21) PRG1_PRU0_GPO10.SPI6_CS2 */
+			J721E_IOPAD(0x7c, PIN_INPUT, 4) /* (AF21) PRG1_PRU1_GPO9.SPI6_CS3 */
+			J721E_IOPAD(0xa0, PIN_INPUT, 4) /* (AJ22) PRG1_PRU1_GPO18.SPI6_D0 */
+			J721E_IOPAD(0xa4, PIN_INPUT, 4) /* (AH22) PRG1_PRU1_GPO19.SPI6_D1 */
+		>;
+	};
+

diff --git a/arch/arm64/boot/dts/ti/k3-j721e-main.dtsi b/arch/arm64/boot/dts/ti/k3-j721e-main.dtsi
index c036df124..edc42720f 100644
--- a/arch/arm64/boot/dts/ti/k3-j721e-main.dtsi
+++ b/arch/arm64/boot/dts/ti/k3-j721e-main.dtsi
@@ -74,6 +74,16 @@
 	    };
 	};
 
+	main_spi6: spi@2160000 {
+		compatible = "ti,am654-mcspi","ti,omap4-mcspi";
+		reg = <0x0 0x2160000 0x0 0x400>;
+		interrupts = <GIC_SPI 190 IRQ_TYPE_LEVEL_HIGH>;
+		clocks = <&k3_clks 272 1>;
+		power-domains = <&k3_pds 272 TI_SCI_PD_EXCLUSIVE>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+	};
+

CONFIG_SPI_OMAP24XX=y is already set in arch/arm64/configs/tisdk_j7-evm_defconfig. The SPI master driver is
drivers/spi/spi-omap2-mcspi.c

2) How to enable SPIDEV on TD4VM SDK?

Add a spidev node inside the spi6 node like below:

+&main_spi6 {
+    pinctrl-names = "default";
+    pinctrl-0 = <&spi6_pins_default>;
+    status="okay";
+
+    spidev@0 {
+
+       spi-max-frequency = <24000000>;
+       reg = <0>;
+       compatible = "linux,spidev";
+};
+};

Enable CONFIG_SPI_SPIDEV=y explicitly in arch/arm64/configs/tisdk_j7-evm_defconfig.

Once you boot Linux one should entries like below:

 ls -l /sys/class/spi*
/sys/class/spi_master:
total 0
lrwxrwxrwx    1 root     root             0 Jun 17 14:17 spi6 -> ../../devices/platform/interconnect@100000/2160000.spi/spi_master/spi6

/sys/class/spidev:
total 0
lrwxrwxrwx    1 root     root             0 Jun 17 14:17 spidev6.0 -> ../../devices/platform/interconnect@100000/2160000.spi/spi_master/spi6/spi6.0/spidev/spidev6.0

3. How to exercise from user space the TI J7/TDA4x SPI interface?

The Linux kernel provides spidev_test tool. We need just build & use that. Follow the instructions here:

cd ti-processor-sdk-linux-automotive-j7-evm-07_00_01/board-support/linux-5.4.40+gitAUTOINC+66cf445b76-g66cf445b76/tools/spi
make ARCH=arm64 CROSS_COMPILE=aarch64-none-linux-gnu-
cp spidev_test /media/$user/rootfs

The above should build spidev_test binary in the tools/spi folder and copy that to rootfs of your target filesystem.

Basic test output:

/spidev_test -v -D /dev/spidev6.0

                                                                                                                                                         
spi mode: 0x0
bits per word: 8
max speed: 500000 Hz (500 KHz)
TX | FF FF FF FF FF FF 40 00 00 00 00 95 FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF F0 0D  |......@.........................|
RX | FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF  |................................|

We can use our own TX and check if TX line is transmitting custom TX bytes using:

 /spidev_test -v -D /dev/spidev6.0 -p "HELLOWORLD"
spi mode: 0x0
bits per word: 8
max speed: 500000 Hz (500 KHz)
TX | 48 45 4C 4C 4F 57 4F 52 4C 44 __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __  |HELLOWORLD|
RX | FF FF FF FF FF FF FF FF FF FF __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __  |..........|

Since there is no Slave the RX we always see 0xFF.

Please find the patch attached here:0001-arm64-dts-ti-k3-j721e-common-proc-board-Enable-spi6-.patch

spidev_test binary attached here: spidev_test

Best Regards,
Keerthy