From: Wei Huang <wei@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>,
Shannon Zhao <shannon.zhao@linaro.org>
Cc: QEMU Trivial <qemu-trivial@nongnu.org>,
Michael Tokarev <mjt@tls.msk.ru>,
QEMU Developers <qemu-devel@nongnu.org>,
Shannon Zhao <zhaoshenglong@huawei.com>
Subject: Re: [Qemu-devel] [PATCH 1/1] arm: virt: change GPIO trigger interrupt to pulse
Date: Fri, 26 Feb 2016 09:28:41 -0600 [thread overview]
Message-ID: <56D06F29.7040106@redhat.com> (raw)
In-Reply-To: <CAFEAcA8DE2Sx4+Rm8cg-tLktW0hz9VcV_7O2jWN5OeA9CwyF4w@mail.gmail.com>
On 02/26/2016 09:06 AM, Peter Maydell wrote:
> On 26 February 2016 at 14:54, Shannon Zhao <shannon.zhao@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
>
next prev parent reply other threads:[~2016-02-26 15:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 18:22 [Qemu-devel] [PATCH 1/1] arm: virt: change GPIO trigger interrupt to pulse Wei Huang
2016-01-29 10:10 ` Shannon Zhao
2016-01-29 14:35 ` Wei Huang
2016-01-29 14:46 ` Shannon Zhao
2016-01-29 14:50 ` Wei Huang
2016-01-29 15:22 ` Shannon Zhao
2016-01-29 14:50 ` Peter Maydell
2016-01-29 15:13 ` Wei Huang
2016-01-29 15:29 ` Peter Maydell
2016-02-01 10:17 ` Igor Mammedov
2016-02-01 17:24 ` Wei Huang
2016-01-30 8:18 ` Shannon Zhao
2016-02-03 7:15 ` Michael Tokarev
2016-02-03 10:46 ` Peter Maydell
2016-02-03 16:01 ` Wei Huang
2016-02-04 1:44 ` Shannon Zhao
2016-02-04 6:10 ` Wei Huang
2016-02-04 6:51 ` Shannon Zhao
2016-02-09 22:59 ` Wei Huang
2016-02-20 10:53 ` Shannon Zhao
2016-02-24 22:22 ` Wei Huang
2016-02-26 12:31 ` Shannon Zhao
2016-02-26 12:53 ` Peter Maydell
2016-02-26 14:54 ` Shannon Zhao
2016-02-26 15:06 ` Peter Maydell
2016-02-26 15:28 ` Wei Huang [this message]
2016-02-26 15:42 ` Peter Maydell
2016-02-27 1:55 ` Shannon Zhao
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