On 02/26/2016 09:06 AM, Peter Maydell wrote: > On 26 February 2016 at 14:54, Shannon Zhao <shannon.z...@linaro.org> wrote: >> On 2016/2/26 20:53, Peter Maydell wrote: >>> I don't understand why a 500ms pulse is better than a short one. >>> >> Oh, I just pick a value which seems like a real latency for pressing a >> button. What's your suggestion? > > I would prefer to avoid the pain of having a timer whose state > needs to be migrated. It's unclear to me why a 500ms pulse > will solve anything that an instantaneous pulse does not, > so I'd like to better understand the problem first.
The problem we found with pulse was: only the last state change in GPIO is received by guest VM. In other words, with 0(L)->1(H)->0(L) or 1(H)->0(L)->1(0), PL061 only sees the last state (0 and 1). I guess this is because QEMU is non-preemptive. The solution is to have the following steps: * qemu_set_irq(gpio_in, 1) * yeild to guest VM * qemu_set_irq(gpio_in, 0) Is there any way to do so in QEMU without using timer? > > thanks > -- PMM >
