On Tue, Apr 25, 2017 at 12:11:00PM +0200, Richard Henderson wrote:
On 04/23/2017 11:54 PM, Stafford Horne wrote:
The OpenRISC architecture has the Power Management Register (PMR)
special purpose register to manage cpu power states. The interesting
modes are:
* Doze Mode (DME) - Stop cpu except timer & pic - wake on interrupt
* Sleep Mode (SME) - Stop cpu and all units - wake on interrupt
* Suspend Model (SUME) - Stop cpu and all units - wake on reset
The linux kernel will set DME when idle.
And SUME would be, essentially, poweroff? Perhaps at least for the purposes
of QEMU; on real hardware one could press a button to assert reset and
reboot.
Yes, that is what I am thinking, but I could add this later, after some
reviews with other OpenRISC folks.
Also, I don't know if its due to this patch of an issue with the timer
interrupts. After applying this patch the timer interrupts do not trigger
until a keypress is make. i.e. something like this...
$ sleep 5
<hangs forever until a key is pressed>
...
+ cpu_restore_state(cs, GETPC() + 4);
This isn't correct. You want
cpu_restore_state(cs, GETPC());
cs->env.pc += 4;
So what's happening is that you're re-executing the MTSPR and going back to
sleep again. Which probably explains the hang.
I have changed to the above, but I think its essentially the same. It
resumes after the MTSPR in both cases.
I fixed this now though, you should see another patch. The issue is the
timer events get ignored once the cpu is in halt state, I added a
qemu_cpu_kick() call in the timer hardware to wake up the cpu on timer
interrupts. Not sure if thats the best way to do it, but it works 100%
now.