7.14. riscv (RISC-V)

7.14.1. riscv

This BSP offers 13 variants:

  • rv32i
  • rv32iac
  • rv32im
  • rv32imac
  • rv32imafc
  • rv32imafd
  • rv32imafdc
  • rv64imac
  • rv64imac_medany
  • rv64imafd
  • rv64imafd_medany
  • rv64imafdc
  • rv64imafdc_medany

Each variant corresponds to a GCC multilib. A particular variant reflects an ISA with ABI and code model choice.

The basic hardware initialization is not performed by the BSP. A boot loader with device tree support must be used to start the BSP, e.g. BBL. The BSP must be started im machine mode.

The reference platform for this BSP is the Qemu virt machine.

7.14.1.1. Build Configuration Options

The following options are available at the configure command line.

BSP_PRESS_KEY_FOR_RESET
If defined to a non-zero value, then print a message and wait until pressed before resetting board when application terminates.
BSP_RESET_BOARD_AT_EXIT
If defined to a non-zero value, then reset the board when the application terminates.
BSP_PRINT_EXCEPTION_CONTEXT
If defined to a non-zero value, then print the exception context when an unexpected exception occurs.
BSP_FDT_BLOB_SIZE_MAX
The maximum size of the device tree blob in bytes (default is 65536).
BSP_CONSOLE_BAUD
The default baud for console driver devices (default 115200).
RISCV_MAXIMUM_EXTERNAL_INTERRUPTS
The maximum number of external interrupts supported by the BSP (default 64).
RISCV_ENABLE_HTIF_SUPPORT
Enables the HTIF support if defined to a non-zero value, otherwise it is disabled (disabled by default).
RISCV_CONSOLE_MAX_NS16550_DEVICES
The maximum number of NS16550 devices supported by the console driver (2 by default).
RISCV_RAM_REGION_BEGIN
The begin of the RAM region for linker command file (default is 0x70000000 for 64-bit with -mcmodel=medlow and 0x80000000 for all other).
RISCV_RAM_REGION_SIZE
The size of the RAM region for linker command file (default 64MiB).

7.14.1.2. Interrupt Controller

Exactly one Core Local Interruptor (CLINT) and exactly one Platform-Level Interrupt Controller (PLIC) are supported. The maximum number of external interrupts supported by the BSP is defined by the RISCV_MAXIMUM_EXTERNAL_INTERRUPTS BSP option.

7.14.1.3. Clock Driver

The clock driver uses the CLINT timer.

7.14.1.4. Console Driver

The console driver supports devices compatible to

  • “ucb,htif0” (depending on the RISCV_ENABLE_HTIF_SUPPORT BSP option),
  • “ns16550a” (see RISCV_CONSOLE_MAX_NS16550_DEVICES BSP option), and
  • “ns16750” (see RISCV_CONSOLE_MAX_NS16550_DEVICES BSP option).

They are initialized according to the device tree. The console driver does not configure the pins or peripheral clocks. The console device is selected according to the device tree “/chosen/stdout-path” property value.

7.14.2. griscv

This RISC-V BSP supports chips using the GRLIB.