Late to the party. Porting aarch64 RPi3B+ to aarch64 RPi4B

[colinh]

I know this sort of things gets asked ad nauseam (at least, when a new processor comes out), but ancient posts seem to lose relevance with time :-/

Do I just need to:

* change peripherals base from 0x3f000000 to 0xfe000000

* add enable_gic=0 arm_peri_high=0 arm_64bit=1 to config.txt

I'm hoping mailboxes, MMU, SD/eMMC, DMA etc. haven't changed?

There's some code (like openocd ?) that just uses NOP loops (for very short delays). I guess these need to be modified?

PS. how does CPU throttling work? Is it automatic and only due to overheating? Or does Linux throttle down when it's idling?

[colinh]

Hmmm. Well GPIO pull-up/down configuration seems to have changed...

Code: Select all

.equiv GPIO_GPPUD,              0x00000094          // RPi 1-3
.equiv GPIO_GPPUDCLK0,          0x00000098
.equiv GPIO_GPPUDCLK1,          0x0000009C
.equiv GPIO_Test,               0x000000B0

.equiv GPIO_PUP_PDN_CNTRL_REG0, 0xe4                // *** RPi4 changed! ***
.equiv GPIO_PUP_PDN_CNTRL_REG1, 0xe8
.equiv GPIO_PUP_PDN_CNTRL_REG2, 0xec
.equiv GPIO_PUP_PDN_CNTRL_REG3, 0xf0

[pmoore]

That's a good start, but the hardware random number generator (rng) has changed, and usb now has a standard xhci controller over pcie (although the old usb interface is still present, and can be enabled in the config.txt, iirc). I believe the ARM is driven by a 54MHz crystal instead of a 19.2MHz now too.

There may be other things too, but those are the ones that I needed to update in my project.

If it helps, this is how I interface with both RNGs of rpi3b and rpi4: https://github.com/spectrum4/spectrum4/ ... rnel/rng.s

To determine at runtime if you are on a rpi3b or a rpi4b, read ARM register midr_el1 then AND with 0xfff0. 0xd030 => raspberry pi 3b.

Example: https://github.com/spectrum4/spectrum4/ ... #L465-L538

[rpdom]

Hmmm. Well GPIO pull-up/down configuration seems to have changed...

Yes. You can actually read the current pull state on the BCM2711. Previous chips were write-only.

[colinh]

Hmmm. Well GPIO pull-up/down configuration seems to have changed...

Yes. You can actually read the current pull state on the BCM2711. Previous chips were write-only.

Ah, I was just wondering why raspi-gpio didn't say anything about the pull state on the RPi 3...