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.
CortexR52 can have a optional FPU.
- VFPv3 with FP16
- Option 1: 16 x double-prevision registers - -mfpu=vfpv3-d16-fp16
- Option 1: 32 x double-prevision registers - -mfpu=vfpv3-fp16
Summary:
- I noticed that ./tools/configure.sh fvp-armv8r:nsh_smp shows
warning: (ARCH_CHIP_FVP_R52 && ARCH_CHIP_FVP_R82) selects ARMV8R_HAVE_GICv3 which has unmet direct dependencies (ARCH_ARM && ARCH_ARMV8R)
- I think ARMV8R_HAVE_GICv3 is only used for aarch32.
- This commit fixes this issue.
Impact:
- None
Testing:
- Tested with nsh_smp on FVP
Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>
This adds functionality to map pages dynamically into kernel virtual
memory. This allows implementing I/O remap for example, which is a useful
(future) feature.
Now, the first target is to support mapping user pages for the kernel.
Why? There are some userspace structures that might be needed when the
userspace process is not running. Semaphores are one such example. Signals
and the WDT timeout both need access to the user semaphore to work
properly. Even though for this only obtaining the kernel addressable
page pool virtual address is needed, for completeness a procedure is
provided to map several pages.
During initialization it isn't possible to use up_puts once it's
protected against concurrent access through a mutex lock. Instead,
using up_putc makes it similar to ESP32S2 and ESP32S3 and perfectly
fits for showprogress usage.
Basic work required for uniprocessor CortexR52 (ARMv8R AARCH32) using
GICv3 and CP15 mapped arch timer.
Tested on ARM FVP 11.20.
Port is based on ARMv8R AARCH64 and ARMv7R code. Excuse possible copy-paste leftovers.
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.
Add an interface that validate if EasyDMA transfer is possible.
EasyDMA cannot access flash memory which can cause hard to detect silent bugs.
This feature is enabled if CONFIG_DEBUG_FEATURES=y and CONFIG_DEBUG_ASSERTIONS=y.
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.
