Jetson Orin Nano - Unable to lower SPI clock speed

[cduarte0306]

Hello,

I have SPI configured on my Jetson Orin Nano but I am unable to lower the speed below 3.2 MHz

root@rc-car-machine:~# spidev_test -D /dev/spidev0.0 -s 1000000 -v
spi mode: 0x0
bits per word: 8
max speed: 1000000 Hz (1000 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 | 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  |................................|
root@rc-car-machine:~# cat /sys/kernel/debug/clk/clk_summary | grep spi
       qspi1_2x_pm                    0        0        0   199999804          0     0  50000         Y
          qspi1_pm                    0        0        0   199999804          0     0  50000         Y
       qspi0_2x_pm                    0        0        0   199999804          0     0  50000         Y
          qspi0_pm                    0        0        0    99999902          0     0  50000         Y
    spi5                              0        0        0    81600000          0     0  50000         Y
    spi4                              0        0        0    81600000          0     0  50000         Y
    spi3                              0        0        0    81600000          0     0  50000         Y
    spi2                              0        0        0    81600000          0     0  50000         Y
    spi1                              0        0        0     3187500          0     0  50000         Y
root@rc-car-machine:~# cat /sys/firmware/devicetree/base/compatible
oe4t,p3768-0000+p3767-0000+tegrademonvidia,p3768-0000+p3767-0000-supernvidia,p3767-0000nvidia,tegra234root@rc-car-machine:~#

Is there a device tree setting I need to modify in order to achieve lower frequencies?

[madisongh]

Have you looked at the kernel documentation on SPI interfaces, the driver for the specific SPI controller that you're using (and its device tree bindings documentation), and/or the Orin technical reference manual? Those would be the first places I'd look to investigate what the supported frequencies are on that interface and how to set them.