[Milkymist-devel] QEMU/UART and HLT

[Takeshi MATSUYA]

Hi,Michael

On 2010/01/25, at 7:27, Michael Walle wrote:
> the output from userspace to the UART is really slow.
> The kernel messages are processed normally.
>
> It seems, that one character needs one timer tick until it gets passed to the 
> UART hardware.
>
> Takeshi, can you have a quick look at your uart driver and test it with the 
> HEAD of my qemu-lm32? Maybe my interrupt handling is still fucked up, but on 
> the other side, within the kernel the output works as expected.

When I tested the following commands, it took about 100 millisecond. 
It seems like there is no problem.
What test did you do?

  root:/> ls -la /etc/services
  -rw-r--r--    1 root     root         8205 Feb  6  2008 /etc/services
  root:/> cat /etc/services >/dev/ttyS0
  root:/> 

> Besides that, you could add the instruction
>  and r0, r0, r0
> to idle loop of the kernel. QEMU interprets this opcode as a HLT instruction, 
> so it doesn't need 100% cpu on the host system.

Thanks,
I will try.

Takeshi