I want to use two pins on the AML-S905X-CC, pins 16 and 18 on header 7J1, as interrupt inputs. Would it be possible to confirm if those are interrupt-capable or if most/all of the available GPIO pins are?
Not sure about the state of interrupts on specific pins but you can google meson pinctrl interrupt. I faintly remember there being some limitations about the number of interrupts. Jerome did it 5 years ago when we first launched Le Potato so best to check and test.
Thanks! From what I can find the interrupt controller in the Meson chips presents 8 hardware interrupts in total, that can be mapped to nearly any GPIO pin. I can see various iterations of kernel patches from ~2016-2017, I’ll see if I can find the equivalent references in the current kernel version.
This seems to be related: GPIOMON does not work on a Le Potato running your suggested Ubuntu image - #4 by Brad_Wigton
I think Armbian with its Linux 5.10 kernel supports the 8 interrupts. I’m not sure why this is not working in Linux 5.19. We are researching this issue.
Thanks! I have not gotten around to writing the dts overlay files I needed yet but I will look at Armbian as well.
Just to update you, the Amlogic GXL family has an interrupt controller that is able to monitor up to 8 interrupts. Each monitored interrupt can be falling or rising edge and monitoring both counts as 2 interrupts. So it’s very limited and reserved mostly for device-tree bound devices. You can look at the dtoverlays in the libretech-wiring-tool to see how it’s done. Due to the small number of monitorable interrupts, it is easy to exceed this if gpio_to_irq is enabled so upstream decided to leave that disabled for this SoC family. This effectively prevents gpiomon from working.
That works, thank you. I have been using spicc-ce1-ads7846-irq-22.dts and spicc-mcp2515-can0.dts as references to write overlays for PPS and the SC16IS752 (and ultimately more variants for SC16IS75x/76x) but have been short on time to work on it.
Feel free to send a pull request if it is a mass market peripheral! As long as the licensing terms are compatible with GPL 2.0.
In this specific case it’s just a custom board for my personal use, but the SC16IS75x/76x family are commonly used SPI/I2C to RS232 from NXP (1 or 2 rs232 ports depending on variants) present on a number of Pi hats, and an overlay for PPS would be useful for anyone who wants to interface a GPS receiver to the S905x for timing purposes (ntp time server, etc.)
I will share the overlay files when they are ready and tested.
Maes, any update on an overlay for PPS? I’ve been trying to write one but get an error from the kernel that it can’t allocate an interrupt:
pps-gpio pps: failed to map GPIO to IRQ: -6