I would try to save you some time.
gpios are driven at the maximum available power on the MCU.
Ref: klipper/src/stm32/gpioperiph.c at master · Klipper3d/klipper · GitHub
SPI hardware block is goofy, so it can only use power-of-2 dividers.
STM32G0 at 64MHz, with a requested 4MHz, would give you that (if you overclock it to 96MHz, it would give you 3MHz on SPI).
STM32H7 at 520MHz, with a requested 4MHz would give you 520_000_000 / 256 = 2031250
Ref: klipper/src/stm32/spi.c at master · Klipper3d/klipper · GitHub
Then there are hardware-specific quirks:
- Octopus Pro (H723), for example, uses https://www.ti.com/lit/ds/symlink/txs0104e.pdf?ts=1763726585684 for 3.3v → 5v level shifting, for the drivers.
- Manta family boards use pull-ups and MOSFET
This limits its ability to do things a little.
For example, I’m sure that I can produce 8..10MHz signal on Octopus even with long cables to magnetic encoders. But we had issues with step/dir on Manta M8P v2 (H723).
So, I expect they would be on the SPI at a comparable frequency.
This does not mean it is bad; it is intended to work with the default configuration.
IIRC, TMC2240 does support the 10MHz SPI.
This does not mean it is bad or something (for any random reader who can read this), just implementation-specific details.
Hope that saves you some time.