Jetson Nano SPI Bus Not Working

Robotics & Edge Computing Jetson & Embedded Systems Jetson Nano
10

Please refer to the following steps for SPI loopback test

Step 1. Connect MOSI and MISO of SPI1
MOSI(PIN19 of 40-pin GPIO header)
MISO(PIN21 of 40-pin GPIO header)

Step 2. Remove GPIO usage of SPI pins
2-1. Check flash log to know which dtb you are using (ex. tegra210-p3448-0000-p3449-0000-b00.dtb)
2-2. Remove GPIO usage in that device tree
2-2-1. Method 1 - Remove from source
diff --git a/kernel-dts/porg-platforms/tegra210-porg-gpio-p3448-0000-b00.dtsi b/kernel-dts/porg-platforms/tegra210-porg-gpio-p3448-0000-b00.dtsi
index 1ea952f..49d4196 100644
--- a/kernel-dts/porg-platforms/tegra210-porg-gpio-p3448-0000-b00.dtsi
+++ b/kernel-dts/porg-platforms/tegra210-porg-gpio-p3448-0000-b00.dtsi
@@ -27,11 +27,6 @@
                gpio_default: default {
                        gpio-input = <
                                TEGRA_GPIO(BB, 0)
-                               TEGRA_GPIO(B, 4)
-                               TEGRA_GPIO(B, 5)
-                               TEGRA_GPIO(B, 6)
-                               TEGRA_GPIO(B, 7)
-                               TEGRA_GPIO(DD, 0)
                                TEGRA_GPIO(E, 6)
                                TEGRA_GPIO(S, 5)
                                TEGRA_GPIO(A, 5)
@@ -49,11 +44,6 @@
                                TEGRA_GPIO(J, 7)
                                TEGRA_GPIO(G, 2)
                                TEGRA_GPIO(G, 3)
-                               TEGRA_GPIO(C, 0)
-                               TEGRA_GPIO(C, 1)
-                               TEGRA_GPIO(C, 2)
-                               TEGRA_GPIO(C, 3)
-                               TEGRA_GPIO(C, 4)
                                TEGRA_GPIO(H, 2)
                                TEGRA_GPIO(H, 5)
                                TEGRA_GPIO(H, 6)

2-2-2. Method 2 - Remove from decompiled dtb
2-2-2-1 Find you dtb in Linux_for_Tegra/kernel/dtb/tegra210-p3448-0000-p3449-0000-b00.dtb

2-2-2-2 Dissemble the dtb to dts
dtc -I dtb -O dts -o temp.dts tegra210-p3448-0000-p3449-0000-b00.dtb

2-2-2-3 Modify the following line
-        gpio-input = <0xd8 0xc 0xd 0xe 0xf 0xe8 0x26 0x95 0x5 0xbc 0xbd 0xbe 0xc1 0xc2 0xa8 0xc8 0xca 0x4d 0x4e 0x4c 0x4f 0x32 0x33 0x10 0x11 0x12 0x13 0x14 0x3a 0x3d 0x3e 0x41 0xe4>;
+        gpio-input = <0xd8 0x26 0x95 0x5 0xbc 0xbd 0xbe 0xc1 0xc2 0xa8 0xc8 0xca 0x4d 0x4e 0x4c 0x4f 0x32 0x33 0x3a 0x3d 0x3e 0x41 0xe4>;

2-2-2-4 Assemble the dts back to dtb
dtc -I dts -O dtb -o tegra210-p3448-0000-p3449-0000-b00.dtb temp.dts

2-2-2-5 Flash the board

Step 3. Running Jetson-IO to enable SPI1
3-1. Run Jetson IO
$ sudo /opt/nvidia/jetson-io/jetson-io.py
3-2. Configure SPI1
Configure Jetson 40pin Header => Configure header pins manually => Select "spi1 (19,21,23,24,26)" => Back -> Save pin changes => Save and reboot to reconfigure pins
3-3. Check pinmux for SPI if the same as following
$  sudo cat /sys/kernel/debug/tegra_pinctrl_reg | grep -i spi
Bank: 1 Reg: 0x70003050 Val: 0x0000e044 -> spi1_mosi_pc0
Bank: 1 Reg: 0x70003054 Val: 0x0000e044 -> spi1_miso_pc1
Bank: 1 Reg: 0x70003058 Val: 0x0000e044 -> spi1_sck_pc2
Bank: 1 Reg: 0x7000305c Val: 0x0000e048 -> spi1_cs0_pc3
Bank: 1 Reg: 0x70003060 Val: 0x0000e048 -> spi1_cs1_pc4
Bank: 1 Reg: 0x70003064 Val: 0x00006044 -> spi2_mosi_pb4
Bank: 1 Reg: 0x70003068 Val: 0x00006044 -> spi2_miso_pb5
Bank: 1 Reg: 0x7000306c Val: 0x00006044 -> spi2_sck_pb6
Bank: 1 Reg: 0x70003070 Val: 0x00006048 -> spi2_cs0_pb7
Bank: 1 Reg: 0x70003074 Val: 0x00006048 -> spi2_cs1_pdd0

Step 4. Probe SPI driver
$ sudo modprobe spidev

Step 5. Download/build this test file:
5-1 Download
$ wget https://raw.githubusercontent.com/torvalds/linux/v4.9/tools/spi/spidev_test.c
5-2 Build on the board
$ gcc -o spidev_test spidev_test.c

Step 6. Run the command and check if the result is expected:
$ sudo ./spidev_test -D /dev/spidev0.0 -v -p "HelloWorld123456789abcdef"
Or 
$ sudo ./spidev_test -D /dev/spidev0.0 -s 10000000 -v
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