Reference:https://xpack.github.io/blog/2022/05/18/riscv-none-elf-gcc-v12-1-0-2-released/
RISC-V ISA updates
Compared to previous releases, starting from 12.x, the compiler implements the new RISC-V ISA, which introduces an incompatibility issue, and builds might throw error messages like unrecognized opcode csrr.
The reason is that csr read/write (csrr*/csrw*) instructions and fence.i instruction were separated from the I extension, becoming two standalone extensions: Zicsr and Zifencei.
The solution is to add _zicsr and/or _zifencei to the -march option, e.g. -march=rv32imac becomes -march=rv32imac_zicsr_zifencei.
Initialize ICACHE way with correct mask.
Initialize scratchpad with constant g_init_marker as it has been done in HSS
Signed-off-by: Jani Paalijarvi <jani.paalijarvi@unikie.com>
Changes the executable type built against the `make export` target fully linked by default. This greatly improves performance when loading applications, as relocations no longer need to be processed.
In the default configuration, the Litex ethernet peripheral contains two RX and two TX buffers. The active buffer for the peripheral should be swapped as soon as possible, in order to reduce packet loss.
This modification acknowledges the receive buffer as soon as the pending data is copied into the NuttX device data buffer. Improving reliability under heavy load.
- Save the FPU registers into the tcb so they don't get lost if the stack
frame for xcp.regs moves (as it does)
- Handle interger and FPU register save/load separately
- Integer registers are saved/loaded always, like before
- FPU registers are only saved during a context switch:
- Save ONLY if FPU is dirty
- Restore always if FPU has been used (not in FSTATE_OFF, FSTATE_INIT)
- Remove all lazy-FPU related logic from the macros, it is not needed
Why? The tcb can contain info that is needed by the context switch
routine. One example is lazy-FPU handling; the integer registers can
be stored into the stack, because they are always stored & restored.
Lazy-FPU however needs a non-volatile location to store the FPU registers
as the save feature will skip saving a clean FPU, but the restore must
always restore the FPU registers if the thread uses FPU.
This adds support for the CoreMMC v3.1 FPGA driver as described
in Microchip Handbook HB0510. The driver doesn't support DMA.
Signed-off-by: Eero Nurkkala <eero.nurkkala@offcode.fi>
If a kernel stack exists, use that whenever the user process is in
privileged mode, i.e. running an exception or in system call. Previously
the exception context was stored into the user's stack, which is not ideal.
Why?
1. Because the exception entry status (REG_INT_CTX) is needed by the
kernel, and this is now in user memory which requires that the correct
user mappings are active when it is accessed.
2. The user must currently account for the exception stack frame (which
is BIG) in its own stack allocation. Moving the exception context save
to the kernel stack offloads this responsibility from the user to the
kernel, which is IMO the correct behavior.
3. The kernel access to user memory is currently allowed without condition,
however this is not ideal either. The privileged mode status CSR allows
blocking access to user memory via the STATUS_SUM-bit, which should be
disabled by default and only enabled when access to user space is really
needed. This patch allows implementing such features.
This is preparation to use kernel stack for everything when the user
process enters the kernel. Now the user stack is in use when the user
process runs a system call, which might not be the safest option.
This is a minimalistic SBI implementation for NuttX.
Provides a single service for now:
- Access to machine timer
Provides a start trampoline to start NuttX in S-mode:
- Exceptions / faults are delegated to S-mode.
- External interrupts are delegated to S-mode.
Machine mode timer is used as follows:
- The timer compare match register reload happens in M-mode, via
call gate "riscv_sbi_set_timer"
- The compare match event is dispatched to S-mode ISR, which will
notify the kernel to advance time
- Clearing the STIP interrupt does not work from S-mode,
so the call gate does this from M-mode
The only supported (tested) target for now is MPFS.
Remove unnecessary reading of the status register when loading / unloading
the FIFOs. Reading from the IP block is slow due to BUS synchronization and
this basically makes the SPI busy loop for no reason at all, destroying the
CPU usage.
The overall benefit of these changes is approx. 25%-points, which is a
MASSIVE improvement.
Adds a driver for an FPGA fabric / CoreSPI implementation.
Supports multiple instances, assuming they reside in some base address,
offsettable by a constant value.
External function to query vbus status. Reading from the block requires
the clock, but if no devices are open -> vbus detect does not work.
This creates a chicken / egg problem, if vbus detect is used to start
the usb device.
bmp388 works poorly as the system fires STOPs even in
a beginning of a transaction. Don't let unrelated STOPs
to distort the data flow.
Signed-off-by: Eero Nurkkala <eero.nurkkala@offcode.fi>
