[RFC PATCH 00/17] sunxi: rework pinctrl and add T113s support

[Sam Edwards]

Hi Andre,

On 12/5/22 17:45, Andre Przywara wrote:
> Please let me know if you have any opinions!

I believe I promised you last month I'd let you know once I had a build 
I'm happy with, and I'm pleased to say that I think I've reached that 
point. I'm running quite rapidly out of sharp edges to sand down, too.

I have a build of U-Boot for my target, complete with:
- UART3 initialized correctly
- DRAM coming up correctly
- SPL sets configured boot clock correctly
- SPI-NAND support (SPL and U-Boot proper)
- MMC support (SPL and U-Boot proper)
- SPL boot from FEL
- USB gadget support
- Ethernet MAC+PHY support
- I²C support *
- GPIO support (LEDs, buttons, misc. board management)
- `reset` working (requries CONFIG_SYSRESET unset, WDT key)
- PSCI, nonsec
- Able to boot Linux ;)

* Requires nonzero `MVTWSI_CONTROL_CLEAR_IFLG` for NCAT2, and a patch to 
the pinctrl driver to configure the proper mux function for my necessary 
pins.

I figured I'd share this list as a sort of checklist for your own work, 
too. The remainder of my efforts now will probably be focused on 
mainlining this stuff (let me know how else I can be of help), and then 
I'm afraid I'll have to disappear back downstream to the Turing Pi 2 
development effort, but maybe our paths will cross again in the kernel 
lists. :)

Thank you greatly,
Sam

P.S. I figure the reason there aren't I²C function defs in the d1 
pinctrl table already is because Allwinner tends to kick around the I²C 
mux values a lot and we would need a per-pin lookup table that would eat 
up too much valuable image space?

In an entirely JUST FOR FUN exercise to give myself a break from staring 
at datasheets/patches and do a "pure CS" coding challenge for a change, 
I came up with a terse encoding scheme for this table. Here is the size 
(in bits) for a selection of D1's functions (pin assignments harvested 
from Linux):

  'emac': 50,
  'i2c0': 101,
  'i2c1': 64,
  'i2c2': 109,
  'i2c3': 91,
  'mmc0': 23,
  'mmc1': 23,
  'mmc2': 20,
  'spi0': 41,
  'spi1': 48,
  'uart0': 78,
  'uart1': 87,
  'uart2': 88,
  'uart3': 102,
  'uart4': 68,
  'uart5': 66,

...and yes, it also identifies invalid pin assignments! I'd be willing 
to contribute something like this if there's big interest, but I figure 
needing to compress this at build-time might be a bit too complicated 
for the U-Boot project's liking.