nerves-project
Update PRU driver
As stated in the provisioning.conf, uboot_overlay_pru is currently broken due to changes in the kernel.
However, it works fine in BeagleBoard's latest distro, AM335x 11.7 2023-09-02 4GB microSD IoT, which also uses kernel 5.10.
Here's my uEnv.txt:
uname_r=5.10.168-ti-r71
enable_uboot_overlays=1
uboot_overlay_pru=/lib/firmware/AM335X-PRU-RPROC-4-19-TI-00A0.dtbo
enable_uboot_cape_universal=1
console=ttyS0,115200n8
cmdline=coherent_pool=1M net.ifnames=0 lpj=1990656 rng_core.default_quality=100 quiet
The system starts up and it's possible to load a new firmware onto the PRU.
A similar config in Nerves breaks the system:
cmd("fw_setenv enable_uboot_overlays 1")
cmd("fw_setenv uboot_overlay_pru /lib/firmware/AM335X-PRU-RPROC-4-19-TI-00A0.dtbo")
cmd("fw_setenv enable_uboot_cape_universal 1")
Perhaps, it's necessary to use a different version of AM335X-PRU-RPROC-4-19-TI-00A0.dtbo?
Unfortunately, I'm not familiar with the topic enough to contribute anything else.
I'm currently not using the PRUs and haven't for years. They definitely did work with nerves_system_bbb at one time, but I think Linux or BeagleBoard changed how they wanted things to work and I got it wrong.
My memory is that there were two ways of interacting with the PRU. One is via UIO and the other is via RPROC. You found the RPROC way. The UIO way is to use AM335X-PRU-UIO-00A0.dtbo. Based on your report, I think that I got confused and thought that they were changing to UIO back when two ways were introduced. This was quite a long time ago.
I don't know if UIO is even viable for the PRUs these days, but if it is, I think it will work. I think that there are Linux device drivers that need to be enabled to support the AM335X-PRU-RPROC-4-19-TI-00A0.dtbo overlay. It's probably enabling one or two kernel options. I don't have access to a Linux machine this evening to poke around and take a guess. A good hint would be for you to run lsmod on the Beagleboard distro. I would expect kernel modules that have pru or rproc in their name to show up. Sorry about not having a better answer now. I'll should have access to a Linux machine next week.
Thank you for the response!
As it stands, both AM335X-PRU-UIO-00A0.dtbo and AM335X-PRU-RPROC-4-19-TI-00A0.dtbo crash the Nerves system.
Here's the output of lsmod for 4 different configurations:
(Module order is listed as it was outputted. Dashes were used for clarity)
| Default | RPROC | UIO | Working UIO |
|---|---|---|---|
| pru_rproc | pru_rproc | - | - |
| irq_pruss_intc | irq_pruss_intc | - | - |
| pm33xx | pm33xx | pm33xx | pm33xx |
| pruss | pruss | - | - |
| - | - | - | uio_pruss |
| - | pvrsrvkm | pvrsrvkm | pvrsrvkm |
| - | - | uio_pruss | - |
| ti_eqep | ti_eqep | ti_eqep | ti_eqep |
| counter | counter | counter | counter |
| c_can_platform | c_can_platform | c_can_platform | c_can_platform |
| c_can | c_can | c_can | c_can |
| can_dev | can_dev | can_dev | can_dev |
| evdev | evdev | evdev | evdev |
| wkup_m3_ipc | wkup_m3_ipc | wkup_m3_ipc | wkup_m3_ipc |
| uio_pdrv_genirq | uio_pdrv_genirq | uio_pdrv_genirq | uio_pdrv_genirq |
| uio | uio | uio | uio |
| cpufreq_dt | cpufreq_dt | cpufreq_dt | cpufreq_dt |
| spidev | spidev | spidev | spidev |
The default configuration doesn't have uboot_overlay_pru at all.
"UIO" configuration doesn't seem to work - there are no uio devices under /dev/
The difference between "UIO" and "Working UIO" is the way uboot_overlay_pru is assigned:
UIO: uboot_overlay_pru=/lib/firmware/AM335X-PRU-UIO-00A0.dtbo
Working UIO: uboot_overlay_pru=AM335X-PRU-UIO-00A0.dtbo
RPROC is enabled via: uboot_overlay_pru=/lib/firmware/AM335X-PRU-RPROC-4-19-TI-00A0.dtbo