[RFC] Bouffalolab Vendor Support

[VynDragon]

Introduction

There is community interest to add support for Bouffalolab SoCs in Zephyr. This RFC was opened to serve as an umbrella to help community and Zephyr members know the initiatives.

Problem description

There is a pull request for the initial support: #78795 .
Work is ongoing for more.

Proposed changes

Give an overview about all pieces required to add Bouffalolab SoCs in Zephyr.

Detailed RFC

In this section of the document the target audience is the dev team. Upon reading this section each engineer should have a rather clear picture of what needs to be done in order to implement the described feature.

Vendor Documentation and SDK

Bouffalolab provides a open source SDK which can be used for reference, especially for peripherals for which the documentation is incomplete or absent.
There is some significant amount of documentation available in https://github.com/bouffalolab/bl_docs .

HAL

There is no HAL per se for Bouffalolab devices, the only materials from the vendor that are directly used are the headers providing peripheral register lists. These headers are Apache 2 and we are awaiting Bouffalolab confirmation for their usage in a zephyr HAL repository.

CPUs

Bouffalolab SoCs use various CPU designs: from SiFive (SiFive E24 on BL60x, BL70x and BL70xL), and from Xuantie T-HEAD (E907 on BL61x, and C906, E907, E902 on BL808 and BL606P).
SiFive E24 Reference Manual is available from sources such as starfive or alibaba. Xuantie CPUs reference manuals are available directly on Xuantie's website after registration.

Caches

Xuantie CPUs provide instruction caches and branch prediction, configured via the XTHeadCMO RISCV extension and various CSR.
The SiFive E24 used in BL60x and BL70x do not provide a cache, but Bouffalolab uses a peripheral, called L1C (Level 1 Cache) to use part of the ITCM from E24 as a fast instruction cache.
BL60x, BL70x, and BL61x rely heavily on these caching mechanisms due to slow flash, with 16KB to 48KB dedicated to instruction caching on the fastest memory in the device, it is recommended to pay close attention to it.
Examples of using those mechanisms and their pitfalls within zephyr are available in the initialization code, the flash driver, and the BL61x USB driver. It is very critical in drivers interacting with the flash or DMA.

Availability for developers

Devboards and modules for BL60x and BL61x are easily available from AI-Thinker, Pine64, and Sipeed via typical channels (Amazon, Aliexpress, LCSC...).
Devboards and modules for BL70x are sometimes available from XT/DOIT. Some noname boards are also available. It is also embbeded in some Sipeed products, such as the RV-debugger.
Devboards and modules for BL808 are available from Sipeed and Pine64.
BL606P is so far only available in the Pine64 PineVox.
TG7100C is a alternative packaging of BL602, available from AI-Thinker via typical channels.
Xiaomi offers modules for BL616 and BL602 at https://iot.mi.com/moduleBrowser.html
Qualcomm offers BL61x as QCC74x.

Peripherals Drivers

Most peripherals are either the same or very similar between SoCs. It is recommended to implement drivers in a way that make them usable for all SoCs.

Task List

Essentials

Essentials are understood to be:

• HAL repository HAL module request: hal_bouffalolab #84174
• CPU support
  BL60x, BL70x, and BL61x can use riscv-privileged arch in CLIC vectored mode, and so all the basic features are supported out the box by Zephyr once the right settings are set.
• SoC initialization
• USART driver
• Interrupts
• GPIO driver
• PinCtrl driver
• System Timer driver drivers: timer: Enable clic riscv machine timer #84103

The initial support will be submitted in a series:

• Introduce Bouffalo Lab SoC's [patch 1] #84173

Future

• 72102 Clock driver for BL60x
• 72102 Clock driver for BL61x
• 72102 Clock driver for BL70x

SoCs

• BL60x: BL602, BL604
  Introduce Bouffalo Lab SoC's #78795
• BL70x: BL702, BL706
  Complete: https://github.com/VynDragon/zephyr/tree/bflb_upstreaming_efuse
• BL61x: BL616, BL618
  Mostly Complete (no AUPLL init): https://github.com/VynDragon/zephyr/tree/bflb/bl61x
  https://github.com/VynDragon/zephyr/tree/bflb/bl61x_usb
• BL70xL: BL702L, BL704L
• BL808
• BL606P
• LF68x: LF686 (BL602), LF688 (BL604)
• TG7100C (BL602)

Boards

• bl604e_iot_dvk (BL604)
  Introduce Bouffalo Lab SoC's #78795
• dt_bl10_devkit (BL602)
• dt_XT-ZB1-DevKit (BL702)
• ai_WB2-12F-Kit (BL602)
• ai_WB2-32S-Kit (BL602)
• ai_M62-12F-Kit (BL616)
• ai_M62-32S-Kit (BL616)
• ai_M61-32S-Kit (BL618)
• ai_TG-12F-Kit (TG7100C)
• sipeed_M0P-Dock (BL618)
• sipeed_M0s-Dock (BL616)
• sipeed_M0sense (BL702)
• sipeed_M1s-Dock (BL808)
• pine64_PineVox (BL606P)
• pine64_Ox64 (BL808)
• pine64_PineCone (BL602)
• others_BL702S-Blue (BL702) https://aliexpress.com/item/1005005927910587.html keyword 'BL702S'
• others_BL616-Blue (BL616) https://aliexpress.com/item/1005006916672346.html keyword 'BL616'

Drivers

Drivers are 'complete' if they support all currently complete SoCs.

• ADC
  Complete in: https://github.com/VynDragon/zephyr/tree/bflb/bl61x
• Audio ADC
• CAM (DVP)
• Audio DAC
• DAC
  https://github.com/VynDragon/zephyr/tree/bflb/bl61x but for BL61x
• DBI
• DMA
• Ethernet EMAC
• Efuses (dependency)
  Complete in: https://github.com/VynDragon/zephyr/tree/bflb/bl61x
• Flash Single Bank
  Complete in: https://github.com/VynDragon/zephyr/tree/bflb/bl61x
• Flash Multi Banks
• GPIO FIFO Mode
• I2C
  Complete in: https://github.com/VynDragon/zephyr/tree/bflb/bl61x
• I2S
• IR
• JDEC
• KeyScan
• LINbus
• LPM (Low Power Modes)
  Work Started in: https://github.com/VynDragon/zephyr/tree/bflb/bl61x_usb
• MJPEG
• PIR Sensor Controller
• PMP
• PSRAM
• PWM
• QDEC (rotary encoders)
• Security Engine/Accelerator
• SDH
• SDIO
• SPI
  Complete in: https://github.com/VynDragon/zephyr/tree/bflb/bl61x
• Timers (!= riscv system timer)
• USB Device BL61x
  Complete in: https://github.com/VynDragon/zephyr/tree/bflb/bl61x_usb
• USB Host BL61x
• USB Device/Host BL808/606P
• USB Device BL70x
• VENC
• BLE BL60x
• BLE BL70x
• BLE BL70xL
• Bluetooth/BLE BL61x
• Bluetooth/BLE BL808/606P
• Wifi Bl60x
• Wifi BL61x
• Wifi BL808/BL606P
• 802.15.4 BL61x
• 802.15.4 BL70x
• 802.15.4 BL70xL
• 802.15.4 BL808/BL606P

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