On Fri, Feb 11, 2011 at 1:12 AM, Michael Walle <mich...@walle.cc> wrote: > This patch adds general target documentation and a todo list. > > Signed-off-by: Michael Walle <mich...@walle.cc> > --- > target-lm32/README | 46 ++++++++++++++++++++++++++++++++++++++++++++++ > target-lm32/TODO | 3 +++ > 2 files changed, 49 insertions(+), 0 deletions(-) > create mode 100644 target-lm32/README > create mode 100644 target-lm32/TODO > > diff --git a/target-lm32/README b/target-lm32/README > new file mode 100644 > index 0000000..a1c2c7e > --- /dev/null > +++ b/target-lm32/README > @@ -0,0 +1,46 @@ > +LatticeMico32 target > +-------------------- > + > +General > +------- > +All opcodes including the JUART CSRs are supported. > + > + > +JTAG UART > +--------- > +JTAG UART is routed to a serial console device. For the current boards it > +is the second one. Ie to enable it in the qemu virtual console window use > +the following command line parameters: > + -serial vc -serial vc > +This will make serial0 (the lm32_uart) and serial1 (the JTAG UART) > +available as virtual consoles. > + > + > +Programmatically terminate the emulator > +---------------------------------------- > +Originally neither the LatticeMico32 nor its peripherals support a > +mechanism to shut down the machine. Emulation aware programs can write to a > +to a special register within the system control block to shut down the > +virtual machine. For more details see hw/lm32_sys.c. The lm32-evr is the > +first BSP which instantiate this model. A (32 bit) write to 0xfff0000 > +causes a vm shutdown. > + > + > +Special instructions > +-------------------- > +The translation recognizes one special instruction to halt the cpu: > + and r0, r0, r0 > +On real hardware this instruction is a nop. It is not used by GCC and > +should (hopefully) not be used within hand-crafted assembly. > +Insert this instruction in your idle loop to reduce the cpu load on the > +host.
It would be better to use MMIO or privileged instruction for this instead of changing an unprivileged instruction.
