Change NRX offset to `3ff5c000`

[Frostie314159]

While reverse engineering Wi-Fi CSI, I found that the NRX peripheral offset may be wrong. I know, that in the blogpost the address offsets are different, but for the S2 it starts at 3f41c000. Configuring CSI requires five registers, starting from xxxx_c000:

1. 074 - ???
2. c0c - BB_CHAN_FILTER (These are preliminary names, inferred through RE)
3. d04 - ???
4. d08 - ???
5. d0c - BB_CHAN_DUMP
   Their function fits with NRX's purpose of controlling the RX path inside the baseband. Therefore, I suggest changing the offset to the proposed value.

[bugadani]

3ff5c000 is not an address accessible via either PeriBus1 or PeriBus2.

[Frostie314159]

My original message was incorrect. That address is only correct for the ESP32. For the S2 it will be different.

[bugadani]

I'm not entirely sure we should change NRX. esp-idf very consistently uses xxxxc00 as the base address. Without being able to see into the hardware, it seems to me that the registers you found may belong to different logical blocks.

Of course there is the chance that esp-idf's DR_REG_NRX_BASE points in the middle of NRX for some reason, but without knowing the specifics, I'd personally not go around changing addresses.

[Frostie314159]

I definitely understand the argument. My explanation for why it would be different in esp-idf is, since AFAIK the only public register in the whole block is NRXPD_CTRL, because all other registers aren't relevant outside the blob.

Also, keeping NRX at this address would mean, that it's the only peripheral address space, that doesn't start at an address aligned to 4096 bytes. All others start at 3ffx_0000 and are a multiple of 4kB long.

This is only an issue for the register at 3ff5c074, since it's outside any peripheral's address space.