BCM2711
Warning
The support for this chip is experimental. Not all features are implemented and they have not been extensively tested by many users.
Help is wanted if you are interested in supporting a feature or if you’ve found an issue with any of the implementation! See the contributing guidelines.
The BCM2711 is a Broadcom SoC used for the Raspberry Pi 4B board.
CPU: Quad-core ARM Cortex-A72
Interrupt Controller: GIC400
Supported Peripherals
Peripheral |
Support |
|---|---|
I2C |
Full interrupt-based support. No 10b addressing. |
UART |
Mini UART yes, PL011 no |
GPIO |
Partial |
MAILBOX |
Partial (polled method, only commands used by firmware are implemented) |
EMMC2 |
Interrupt-based support, no DMA. |
EMMC |
Supported alongside EMMC2 in theory, but untested. |
PWM |
No |
SPI |
Interrupt-based driver (no DMA) for all SPI except 1 & 2 (auxiliary) |
PCM |
No |
Warning
The SPI driver implemented for the BCM2711 has only been tested on SPI0. It appears that even using the special overlays for the device tree passed to the proprietary firmware does not properly initialize the remaining SPI interfaces, and thus they have not been working properly. More effort is required to reverse engineer the magic incantations required to initialize these interfaces, at which point it is assumed that the driver implementation should extend to SPI3-6.
Warning
The EMMC2 peripheral connects to the microSD card slot on the Raspberry Pi 4B. Currently, it has been tested using a 32GB Samsung microSD card and it has passed testing with that. The only quirks are:
No card insertion/removal interrupts work, so hotswapping isn’t possible
The sdstress example works unless the ‘number of bytes’ option is greater than 1023. I suspect this is something to do with the FIFO depth being only 1023 bytes.
However, the 64GB microSD card exhibits very strange behaviour. There are
often data CRC errors that prevent the boot filesystem from mounting. When
that somehow passes (intermittent), running ls on the filesystem repeatedly
sometimes causes certain files to disappear from the listing (they are not
deleted and appear again on next boot), or causes their filenames to be shown
in all caps. Writing to the card with echo often fails with data CRC
error or timeout, and then the card is buggy for the remainder of the
session. It is not recommended to use 64GB cards with this implementation
for the time being.